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Chapter 3 BASIC

IDAHO MASTER GARDENER UNIVERSITY OF IDAHO EXTENSION

Introduction 2 and Classification 2 3 3 3 and 3 Plant Cycles 6 Annuals 6 Biennials 6 Perennials 6 Plant Parts and Their Functions 7 Vegetative Parts: , Stems, and 7 Reproductive Parts: , , and 10 Plant Development 14 14 Vegetative Growth Stage 14 Reproductive Growth Stage 14 15 Further Reading and Resources 15

CHAPTER 3 BASIC BOTANY 3 - 1 Chapter 3 Basic Botany

Jennifer Jensen, Extension Educator, Boundary County Susan Bell, Extension Educator, Ada County William Bohl, Extension Educator, Bingham County Stephen Love, Consumer Specialist, Aberdeen Research and Extension Center Illustrations by Jennifer Jensen

INTRODUCTION varying from country to country, region to region, and sometimes even within a local area. makes Botany is the study of . To become a it difficult to communicate about a plant. For knowledgeable plant person, it is essential to example, the state of Idaho is understand basic plant science. It is important to lewisii , commonly called in Idaho. In other understand how plants grow, how their various parts parts of the country, however, the same plant is function, how they are identified and named, and known as mock . To add to the confusion, how they interact with their environment. Learning Syringa is the genus for lilac . Another the language of botany means learning many new example of confusing common names is words. Making the effort to learn this material will parviflora , which is called little mallow, round prove extremely valuable and will create excitement mallow, cheeseweed, or sometimes buttonweed. The as you learn to unravel the mysteries of the plant same common name may also be used for several world. plants. An example is the common name , Like all living , plants are complex, and which can refer to plants in either the genus there is far more to know about them than can be Geranium or the genus . learned in an introductory Master Gardener course. With scientific names, a plant has only one name. Nonetheless, this chapter is designed to provide the Scientific names use the language and often Master Gardener student with a brief, but broad, are descriptive of some characteristic of the plant. A introduction to many aspects of botany. dictionary on plant names can help with pronunciation and clarify the meaning of Latin PLANT NOMENCLATURE AND words. CLASSIFICATION Plants are named using a binomial (two-part) Plant classification and the scientific naming of naming system. A binomial name includes the plants are important for correct and precise plant’s genus name (capitalized and italicized) plus identification. Plant classification can be useful for the specific epithet name (lowercased and Master Gardeners involved in identifying plants, italicized). The name may be followed by the initial germinating seeds, growing a garden, diagnosing of the person credited with originally describing and plant problems, or controlling pests. naming the plant. For example, L. indicates that Carl von Linne Plants generally have a common name and a tuberosum (Linnaeus), a Swedish physician, described and scientific name. Common names are usually simple named the white (Irish) . and easy to remember for the general public. They often are descriptive of the plant; for example, Plant classification groups plants with similar burning bush, bleeding heart, or paper . characteristics, first in a broad sense, then through a of subgroups, using progressively more There are problems, however, with using specific flower and plant traits. This process common names. The same species of plant may continues until a single, unique plant remains. have two or more common names, with names

3 - 2 BASIC BOTANY CHAPTER 3 This plant is given a binomial species name. Ranked In a family of plants, similarities occur primarily from general to specific, the plant classification with reproductive parts (flowers, , and seed), groups are as follows: , or , although leaves and other plant parts may also be , , family, genus, species, and variety or similar. Table 2 includes some common families and cultivar. Each species is assigned to a genus, each some of their characteristics. genus to a family, and so on. Refer to Table 1 for Genus examples of plant classification. Genus is a subdivision of a plant family. Plants of Understanding plant classification is useful for the same genus share similarities mostly in flower maintaining a successful garden. For example, characteristics and . Plants in one genus vegetable should be rotated each year, and usually cannot with plants in another, but rotation can be simplified by grouping plants from species within a genus will often intercross. The the same family. To do so, you need to know which first letter of the genus name is capitalized, and the plants belong in which family. A second example: entire name is italicized or underlined. when using the Internet to research solutions to a plant problem, it is absolutely essential to enter the Species correct scientific name. The more you study plants, Species is a group of individual plants that freely the more you likely will appreciate the usefulness of interbreed and have many (or all) characteristics in the scientific nomenclature system. common. Species names use the binomial naming system of genus and specific epithet. An important distinction among plants at the Division level is between those with seedlings Variety and cultivar having one seed leaf ( monocots , such as grasses Variety and lilies) and those with seedlings having two seed Variety is a word commonly used to describe leaves ( dicots , such as beans). Monocot and dicot cultivated and hybridized plant types. This is a seeds germinate differently. The distinction between misnomer; used in its proper context, a variety is a monocots and dicots becomes very important when botanical division of a species. It is a subgrouping using herbicides. For example, common of plants within a species that differs in some herbicides for broadleaf weeds (for example, 2,4-D) particular way from other members of that species. will kill only dicot plants, leaving the grass plants In the wild, variety may be used to describe a (monocots) unharmed. particular regional variant of a species with unique Family plant size, flower color, or other visible trait. In Master Gardeners usually work with the cultivated plants, variety may be used to designate a classification of plants at the family level and below. particular useful form of a species. For example, Plant families are important in gardening because ( oleracea var. botrytis ) and members of the same family often have similar ( var. capitata ) are cultural requirements and similar and varieties of the same species. The variety name disease problems. follows the abbreviation “var.” It is written in lower case and is italicized or underlined.

Table 1. Examples of plant classification.

Common name Black chokecherry Siskiyou blue Idaho fescue Western white Kingdom Planta Planta Planta Division or phylum Magnoliophyta Magnoliophyta Pinophyta Subdivision Angiospermae Angiospermae Gymnospermae Class Magnoliopsida (dicots) Liliopsida (monocots) Pinopsida Order Family Rosaceae Pinaceae Genus Pinus Species Festuca idahoensis Pinus monticola Variety or cultivar var. melanocarpa ‘Siskiyou Blue’

CHAPTER 3 BASIC BOTANY 3 - 3 Table 2. Common plant families.

Scientific Common family name family name Common plants in family Family traits family Carrot ( ) Flowers usually in simple or ( sativa ) compound, flat-topped clusters Dill ( Anethum graveolens ) called ; stems often Poison hemlock ( Conium maculatum ) hollow. Asteraceae or Sunflower family ( sativa ) Flowers organized as heads Compositae Sunflower ( annuus ) with ray and disk flowers. One ( ) of the largest families: 20,000 Spotted knapweed ( stoebe ) species. or Mustard family ( Brassica oleracea var. botrytis ) Flowers have four that Cruciferae ( Brassica oleracea var. acephala ) are not joined; there usually are Cabbage ( Brassica oleracea var. capitata ) six (four long, two Radish ( Raphanus sativus ) short). Shepherd’s-purse ( Capsella bursa-pastoris ) Fabaceae or or bean family Common pea ( Pisum sativum ) Flowers with a distinct upper Leguminosae Common bean ( vulgaris ) “flag” , arranged in heads Lupine ( argenteus ) or spikes. Hairy vetch ( villosa ) or Mint family ( x piperita ) Leaves usually opposite; flowers Labiatae Sweet basil ( Ocimum basilicum ) tubular; stems square. English lavender ( Lavendula angustifolia ) Henbit ( amplexicaule ) Poaceae Grass family Corn ( mays ) Leaves simple and strap-like; Kentucky bluegrass ( pratensis ) usually a long Blue fescue ( ) spike. Large family of between Quackgrass ( Elytrigia repens ) 7,500 and 10,000 species. Buttercup family Columbine ( vulgaris ) Large and variable family with Larkspur ( elatum ) variable flower form; most Lenten ( Helleborus orientalis ) species have showy Creeping buttercup ( repens ) rather than petals. Rosaceae Rose family ( pumila ) Flowers with five (or multiples of Garden ( x ananassa ) five) petals and many stamens Rose ( Rosa spp.) Sulfur cinquefoil ( recta ) Solanaceae Nightshade or ( esculentum ) Leaves alternate; flowers have potato family Pepper ( annuum var. annuum ) five petals fused at the base; Potato ( Solanum tuberosum ) stamens attached to the petals Black henbane ( Hyoscyamus niger ) and form a around the pistil.

3 - 4 BASIC BOTANY CHAPTER 3 Cultivar from hybrids, which are produced through a process This word is a contraction of the term “cultivated that completely controls transfer. Open- variety.” A cultivar is a very specific, -bred, pollinated will grow true-to- if seed is cultivated form of a useful species. If collected from parental plants that are isolated from propagated asexually (vegetatively), cultivars can be other cultivars of the same species. Most lettuce, termed clones . When vegetatively propagated, bean, and pea varieties for home gardeners are cultivars maintain their characteristics from examples of open-pollinated plants. generation to generation, thus preserving desirable Heirloom. No universally accepted definition of traits. However, seeds of clones will not produce heirloom exists. Some people consider varieties to plants with the same desirable characteristics as the be heirlooms only if they are at least 100 years old. cultivar. If propagated by seeds, cultivars can be Other people feel the proper cut-off date is 1951, the termed lines . year recognized as the point at which modern Cultivar names are indicated by placing the term cultivars became available. Nonetheless, there are in single quotation marks or by preceding the two fairly common characteristics attributed to cultivar name with the abbreviation cv. (do not use heirloom cultivars: (1) they are relatively old, and both). The first letter of the cultivar name is (2) they are not currently planted in large-scale capitalized, but the name is not italicized or production . underlined. An example is the tomato cultivar Early Cultivars designated as heirloom have recently Girl, expressed as Solanum lycopersicum ‘Early become very popular in home garden and small Girl’ or cv. Early Girl. agriculture production. They provide unique Both ancient practices of plant and appearance and quality characteristics. However, modern processes of have they also tend to be narrowly adapted and lack the contributed to the vast pool of plants we have pest resistance that is common in modern cultivars. available for , industry, and beautification. The terms “open-pollinated” and “heirloom” are Understanding the titles used to describe these often used synonymously. By any standard used to plants will help in making decisions as to which define heirloom, this is incorrect. Open-pollinated cultivars are suitable for specific uses. refers to any cultivar developed through modern . This term is used to describe a locally (traditional) breeding methods that is not a domesticated and utilized form of a plant species controlled- hybrid. Every year, modern that was developed through a long process of breeding programs release new open-pollinated selection without the use of modern genetics. cultivars of many crops and landscape species. typically have ancient origins, and their Cultivars designated as heirloom, on the other hand, production was historically limited to a very small include many of the older, lesser known open- geographical area. They often are specifically pollinated cultivars, clonal cultivars, and, in some adapted to production conditions typical of their cases, landraces. point of origin. One example is Palomero Hybrid. Hybrid cultivars are often referred to as Toluqueño, a type of popcorn that was historically F1 hybrids. This means that the seed we purchase grown in the highlands of Mexico. and the resulting plants grown are the first- Landraces typically have improved traits that generation offspring of two open-pollinated . make them valuable for human use in comparison (The abbreviation F1 stands for the term “first filial” with the original wild species. At the same time, generation.) Hybrid cultivars are limited almost individual plants within a landrace often vary in exclusively to food plants, with a few exceptions. In appearance, quality, and resistance traits. production agriculture, hybrid cultivars can provide many important advantages, including higher yield, Open-pollinated. These cultivars are developed greater plant uniformity, more consistent quality, through modern breeding practices, genetically and the combination of the superior traits of two stabilized to ensure uniformity, and then seed outstanding parents. propagated using methods that allow uncontrolled distribution of pollen within the crop. They differ

CHAPTER 3 BASIC BOTANY 3 - 5 The main difference between hybrid and open- Annuals pollinated cultivars is that subsequent generations Annuals grow, mature, flower, produce seed, and grown from the seed of a hybrid do not breed true to die in one season. An annual may be a type. Thus, growers cannot collect and use their summer or a . For summer annuals, own seed, but must purchase new seed each year. annual winter annual the seed germinates in the spring, and a plant For this reason, many people do not consider hybrid develops, matures, and produces seed by the end of cultivars sustainable in small-scale agricultural the growing season. Summer annuals include production. , corn, and beans. Winter annual seed Clonal. Many plant cultivars are not propagated germinates in the fall, producing a plant that from seed. They are propagated using vegetative overwinters, matures, and produces seed the parts. Some familiar plants propagated in this following growing season. Winter and downy manner include potatoes, , , bromegrass (a weed) are winter annuals. flowers, and most types of fruit . Types of plant Biennials material used to establish a new generation include tubers, , cuttings, stolons or runners, Biennials take 2 years or at least part of a second pieces, and stem cuttings. Many clonally year to complete their life cycle. During the first produced cultivars can trace their origins to a single season, they grow a hardy of leaves plant discovered many hundreds of years ago. that will overwinter. During the second season, the plant flowers, produces seeds, and then dies. Parsley GMO. Short for “genetically modified and table beets are examples of biennial plants. ,” GMO cultivars are radically different from the cultivar types discussed previously, all of Perennials which have their basis in traditional breeding and/or Perennials live for more than 2 years. selection. Biotechnologists have discovered ways to Herbaceous perennials have soft, nonwoody stems. isolate and remove specific from one Herbaceous perennials die back each winter, and a organism and attach them to the of a new plant grows from the or roots the different organism. This makes it possible to give following spring. Herbaceous perennials may live plants traits that did not provide. for 3 to 25 years, or even longer under ideal growing conditions. Many herbaceous plants, such This technology is widely used in production as tomatoes or (a flowering ), are agriculture to address critical production and perennial in warmer climates, but are grown as nutrition issues. Examples include insect-resistant annuals in temperate climates. corn and cotton cultivars (greatly reducing the need for insecticide use), herbicide-resistant and Woody perennials such as trees or shrubs have a beets (minimizing the need for expensive woody stem or trunk. Those that lose their leaves hand weeding), and cultivars with high levels of every fall and grow new leaves in the spring are vitamin A (reducing the incidence of blindness in called . many developing countries). Currently, there are no Trees or shrubs that keep their leaves (needles or GMO cultivars available for home food production. broad leaves) through the winter are called Many people oppose the use of GMO cultivars, . Sometimes, the term evergreen may be limiting their value for use in small-scale farming or evergreens somewhat of a misnomer because the older needles home production of food crops. (those closer to the trunk) fall off. For example, a spruce tree will hold its needles for 7 to 10 years, PLANT LIFE CYCLES while a pine tree will hold needles for about 3 years. A plant is classified by its life cycle, specifically Woody perennials have a wide range of life how long it and how long it takes to complete spans, ranging from 10 to 12 years for aspens in a reproductive processes and develop seed. home landscape to more than 1,000 years for some . Life expectancy is often linked to growth rates. (Slower growing plants such as bristlecone tend to live longer.)

3 - 6 BASIC BOTANY CHAPTER 3 PLANT PARTS AND THEIR FUNCTIONS Leaf arrangement and shape. Leaves are attached to a stem in one of three patterns: , Vegetative parts: Leaves, stems, and roots opposite alternate , and whorled . Opposite arrangement Understanding plant part terminology (figure 1) means two leaves attach at the same point, but on and the functions of plant parts will help you opposite sides of the stem. With alternate identify plants and diagnose plant problems. arrangement, leaves are attached at alternating points from one side of the stem to the other. In a Leaves whorled arrangement, three or more leaves are Leaves are the main structures produced on plant attached at the same point. Leaf arrangement is stems. Leaves come in many different shapes, sizes, often used for plant identification. For example, and arrangements and are used for plant trees have opposite leaf arrangement, and identification. They also serve many vital roles, the birch and trees have alternate leaf most important being the harvest of light energy. arrangement. The leaf is the primary site of , respiration, and , all important growth Leaves are most often thought of as being flat processes for plants. blades of various shapes. Examples include the leaves of maple trees or green beans. However, a Leaf parts and structure. There are two main leaf blade may be needle-like, such as in conifers. parts to a leaf: the blade (flat, thin portion) and the Spruce trees have about 1-inch-long needles, and . The petiole attaches the blade to the stem pine trees 2- to 3-inch-long needles. Leaves can also and contains conducting tissues between the leaf be scale-like, such as in redcedar and arborvitae, or and the stem. flat and strap-shaped as in grass plants. Leaf shapes The outer cell layers on the top and bottom of the are also helpful for identification. leaf blade are the ; they serve to protect the inner leaf . Specialized epidermal cells on the undersides, and sometimes upper sides, of leaves TERMiNAL form openings called stomata . (The singular of LATERAL BuD stomata is stomate .) Open stomata keep and nutrients moving through the plant and allow the exchange of and oxygen between the NODE air inside and outside the leaf, a process that is iNTERNODE critical for photosynthesis. Conditions that cause LEAF BLADE plants to lose a lot of water (high , wind, low ) cause the stomata to close. PETiOLE Consequently, it is important to keep plants adequately watered to allow air exchange for photosynthesis. Some plant leaves have a waxy layer on the epidermis called the . The cuticle protects the leaf from dehydration and prevents penetration of vASCuLAR SySTEM some disease-causing organisms. The leaf blade texture (smooth, hairy, waxy, etc.) is often important to consider when applying pesticides. For example, herbicides may not make good contact on hairy or waxy leaves; consequently they are less effective. Also, some pesticides may LATERAL PRiMARy ROOT remove a desired waxy leaf texture. When this ROOTS happens on Colorado spruce needles, for example, the color of the needles may change from blue to ROOTS green. Figure 1. Parts of a .

CHAPTER 3 BASIC BOTANY 3 - 7 Photosynthesis in leaves. Plants are able to take potato tubers and . If days are hot and solar energy and turn it into chemical energy are warm, plant growth will be reduced and through the process of photosynthesis. Without yields may decrease. Grasping this relationship photosynthesis, life on would not exist. All between photosynthesis and respiration will help other life forms depend on the oxygen and food that you understand plant growth and yield variability photosynthesis provides. from year to year. Inputs for photosynthesis include carbon dioxide, Transpiration in leaves. The loss of water water, and light. Carbon dioxide enters the leaf through leaf stomata is called transpiration . through the stomata, water enters through the roots, Transpiration pulls water containing dissolved and light energy comes from natural or artificial nutrients from the soil through the roots and the rest light. Outputs of photosynthesis are oxygen and of the plant. It also provides evaporative cooling for carbohydrates. leaf tissue. About 90 percent of the water entering roots is used in transpiration, and the remainder is Gardeners are basically managing a living plant used for photosynthesis. factory. The goal is to maintain plant health and manage the environment so plants can produce the The amount of water used depends on most carbohydrates possible. Anything that damages temperature. As rise, the amount of the leaves (diseases or insect feeding) or reduces water needed increases. Consequently, it is critical their ability to absorb sunlight (too much ) or to irrigate more frequently during warm weather. take in carbon dioxide will limit the photosynthetic Also, plants growing in a dry climate need more capability of a plant. water than those growing in a more humid environment. Respiration in leaves. Respiration is essentially the reverse of photosynthesis. It is the process by Stems which carbohydrates are converted into energy. With The stem is the main above-ground support the production of energy, and oxygen are structure of a plant. It contains the vascular system converted to carbon dioxide, water, and a small that allows water, nutrients, and carbohydrates to amount of heat. Respiration releases energy to build move within a plant. new tissues, maintain chemical processes, and produce growth within the plant. Respiration occurs Parts of a stem. All stems have nodes , where in all cells at as well as during the day, a key leaf attachments occur. Nodes contain that may point that is discussed below. develop into leaves, flowers, or lateral branches. The areas between nodes are called internodes . Relationship between photosynthesis and Plants that grow in reduced light conditions may respiration. The rates of photosynthesis and have very long internodes. respiration depend on temperature. Plants have an optimum temperature range and a maximum It is important to be able to recognize nodes temperature for photosynthesis. The rate of when pruning. For example, it is often necessary to photosynthesis will increase with increasing remove a tree branch back to a node that will temperature up to a certain point and then decrease produce a new stem. Also, when plants are at higher temperatures. Likewise, higher propagated asexually via vegetative cuttings, new temperatures will increase respiration. Unlike roots most often form at nodes. photosynthesis, however, respiration continues to Types of stems. Most stems grow above ground, rise with increasing temperature. and many grow erect (for example, trees, corn, and Photosynthesis does not occur at night, but sunflowers). Some above-ground stems can also respiration does. If nighttime temperatures are too grow along the ground, such as cucumbers and warm, the plant will use all of the energy produced . There are also several other types of by photosynthesis during the day for metabolic stems that gardeners need to understand because processes at night just to stay alive, rather than plants with these modified stems may need to be converting the carbohydrates into new plant cells. managed differently. This can affect the portions that we eat, such as

3 - 8 BASIC BOTANY CHAPTER 3 Crowns are compressed above-ground stems In monocots, the vascular bundles are scattered with very short internodes. Examples of plants with throughout the stem and are not as easily damaged. crowns include dandelions, , rhubarb, asparagus, and many grasses such as Kentucky Buds bluegrass. Rhubarb and asparagus are propagated by A bud is a fully formed but undeveloped or planting crowns. Crown identification is especially flower. If a bud is at the tip of a shoot, it is called a important when planting strawberries, as covering terminal bud . Regardless of location, buds that the crown with soil is detrimental to their growth. form or leaves are vegetative buds . Flower buds produce one or more flowers. Mixed buds Spurs are short, stubby stems commonly found produce both shoots and flowers. on fruit trees such as apple and . Spurs produce fruiting buds. If a severe pruning cut is made close Buds may grow immediately after they are to a spur, the spur may produce a stem rather than formed, or stop growing and remain dormant until the intended fruit. the following spring. Buds on many plants, such as fruit trees, require a specified duration of cold Stolons , also called runners, are horizontal stems, temperature below a critical level before they will either fleshy or semiwoody, that grow on top of the grow in the spring. This cold period is easily soil surface. For example, stolons attach a accomplished in Idaho, but may not be achieved in strawberry plant to its plantlets. Some types of warmer states such as Florida or California. grass, such as creeping bentgrass, form stolons. This species often is planted on golf course putting During , buds can tolerate very low greens. temperatures without damage. However, once the plant has had enough cold temperature to satisfy the are stems that grow below ground. A requirement for growth, a new bud can easily be very popular lawn grass, Kentucky bluegrass, damaged by subsequent cold temperatures. spreads by rhizomes. Another grass that spreads by rhizomes is quackgrass, which is considered a Roots difficult-to-control weed. Roots are often neglected or forgotten while caring for plants because they are not visible. There are several other types of modified stems, However, roots are a critical plant part that such as tubers (the edible part of potatoes) and bulbs gardeners need to understand to properly care for ( and ). These topics are covered in plants. Roots make up a large proportion of the total more detail in the chapter titled “—about 20 to 30 percent of the total volume. Ornamentals.” Small feeder roots are so numerous that the total Vascular system amount of roots can account for up to 90 percent of Plants need a system to transport water and the surface area of a plant! nutrients from the roots to the leaves and to move Establishing a healthy root system is one key to photosynthetic sugars to stems, roots, and other growing attractive and productive plants. The plant parts. You could think of this vascular system importance of roots is evident when transplanting as being similar to the vessels and veins in trees. Transplanted trees often suffer from . There are two types of vessels in “transplant shock” and do not seem to grow well the plants. vessels conduct water and minerals first 2 or 3 years. The problem is the amount of root up from the roots, while phloem tubes carry sugars system that was removed during the transplanting and other compounds from the leaves to the rest of process. Bare-root or balled and burlapped trees the plant. have less than about 5 percent of their original root The xylem and phloem are grouped in vascular system and cannot grow normally until a complete bundles. In dicots, the vascular bundles are arranged new root system has developed. in a continuous ring in the outer perimeter of the Root functions. Roots absorb nutrients and stem. In woody plants (trees and shrubs), these moisture from the soil or growth medium (potting vascular bundles are located just under the bark. soil), anchor the plant, physically support the stem, Thus, they can be easily damaged by lawn mowers, and move water and minerals to the stem. In some string trimmers, or stems rubbing against each other. cases, roots serve as food storage organs. Roots

CHAPTER 3 BASIC BOTANY 3 - 9 profoundly affect the size and vigor of the plant, the Reproductive parts: Flowers, fruits, method of propagation, to soil types, and and seeds responses to cultural practices and irrigation. Flowers Types of root systems. After the primary root Flowers are the sexual reproductive organs of emerges from the seed, it may continue to grow seed-bearing plants, designed to produce and straight down and become a taproot , or it may distribute pollen, accept pollen, provide a way to branch and form a fibrous root system with many fertilize the , and nourish and protect the side (lateral) roots. developing seed (Figure 2). This makes flowers critical to the survival, adaptation, , and Root growth. There is a common misconception that tree roots penetrate the soil to several feet. In distribution of plant species. fact, most of the functional feeder roots of woody Angiosperms produce the reproductive structures plants—those that absorb water and nutrients—are we recognize as flowers and are the group of plants located in the upper 18 inches of soil. Many plants discussed in this . (conifers) have even more shallow root systems. The depth to produce pollen and seeds, but don’t have structures which roots penetrate depends on the plant type, soil recognizable as flowers. Some plants, such as , texture and structure, and water status. A dense, do not produce flowers or seeds and instead compacted soil layer or a high water table will reproduce using . restrict or terminate root growth. Parts of the flower. A typical flower has four Another misunderstanding about roots is that they major parts: sepals , petals , stamens , and pistils . will grow to “find” water. Roots will not grow into However, not all flowers have all four parts. dry soil, so unless soil is moist, roots will not grow Flowers lacking one or more of these basic parts are to their maximum length. called incomplete flowers. In nature, any The roots of most plants are far more extensive combination of flower parts can occur. The shape than the above-ground area beneath the plant. Tree and visibility of flower parts also vary widely roots extend several feet beyond the drip-line of the among plant species. tree. Disturbing the soil by, for example, digging a Sepals are the outer covering of the flower when trench or compacting the soil via vehicular or foot it is in the bud stage. They are usually green and traffic will have an adverse effect on the tree’s leaf-like in appearance. In some plants, they have health.

PETAL

STyLE

PiSTiL ANTHER

STAMEN OvARy FiLAMENT

SEPAL

Figure 2. Parts of a flower.

3 - 10 BASIC BOTANY CHAPTER 3 the form and color of petals (for example, in tulips). lacking tiny fruit under the corolla) and female Collectively, all of the sepals form the calyx . flowers (the ones with a tiny under the corolla) alternate along the (see Table 3 for are usually the largest and most visible Petals additional examples of common monoecious feature of a flower and are commonly brightly species). colored. The color helps attract to pollinate the flower. As a group, the petals form the corolla . Other species may have separate male and female plants, with flowers of only one on any single are the male parts of the flower and are Stamens plant. The term for this arrangement is (a usually found near the center of the flower. Each dioecious Latin term meaning “two houses”). is an flower contains multiple stamens—in some cases example of a dioecious plant. Only the female very large numbers. At the top of each is an plants produce , and only if a male plant is anther sac in which pollen is produced. nearby to supply pollen (see Table 3 for additional The pistil is the female component of the flower. examples of dioecious plants). The upper part of the pistil, called the , stigma For seed to develop, usually has some type of sticky surface designed to Pollination of flowers. pollen must be transferred from the anthers to the trap and accept pollen. The base of the pistil pistil, where it can fertilize the . Some plants contains one or more (eggs) that develop into ovules require a to transfer pollen from flower to seeds after pollination and fertilization. flower. can include many types of Arrangement of male and female flowers. animals, most commonly insects or . Many species of plants produce flowers lacking one Honeybees are an example of common pollinating or more of the sexual parts and are referred to as insects. . Flowers with no pistils are male flowers imperfect Plants that require a pollinator (such as an apple ( ). Flowers with no stamens are female staminate tree) produce sticky pollen that adheres to flowers ( ). pistillate visitors. Other plants, such as corn, utilize the wind Depending on species, imperfect flowers may be for pollination. They release large amounts of small, arranged within and among plants in a number of light, nonsticky pollen grains into the air and rely on ways. Individual plants may produce separate male chance to carry them to the pistil of a nearby plant. and female flowers on the same plant. The term for As a rule, plants that require pollinators have large this arrangement is monoecious (a Latin term and/or showy flowers. Wind-pollinated plants tend meaning “one house”). Cucumbers are an example to have inconspicuous flowers. of this type of plant; the male flowers (the ones

Table 3. Examples of plants with monoecious or dioecious flower arrangement.

Scientific name Common name Monoecious species Betula alba European white birch Curcurbita pepo nigra Black acuminata Quercus macrocarpa Bur Salix matsudana Globe willow Zea mays Corn Dioecious species Box elder Asparagus officinalis Asparagus pennsylvanica Green ash Carpet juniper alba White poplar Spinacia oleracea Spinach cuspidate Japanese yew

CHAPTER 3 BASIC BOTANY 3 - 11 Fruits improper pollination, less-than-ideal growing After pollination, the starts to develop, conditions during seed development, or fruit forms, and seeds enlarge within the fruit. Fruits within a plant for resources can lead to nonviable come in many sizes and forms. They may be fleshy seed. Nonviable seeds may look normal, but will not () or dry (). They can be single () grow, even when planted in optimal conditions. In or aggregated (; the crumbles of a nature, nonviable seeds affect the ability of plants to raspberry are actually individual fruits). They can propagate themselves. In the garden, nonviable have a hard coat (a nut) or soft, fragile skin seeds have a negative impact on plant stands and (tomato). They can hold one seed () or many productivity. Nonviable seeds should not be (cantaloupe). confused with dormant seeds, which are discussed below. The fruit serves to protect the developing seed. Once the seed is mature, the fruit can be important Seeds enable plants to bridge periods of time in seed dissemination. Sweet, edible fruits, such as when growing conditions are not favorable (winter, serviceberries, are often consumed by animals, and dry periods, etc.). Consequently, if conditions are the seed is then deposited elsewhere in their appropriate, seeds of most plant species can remain droppings. Other types of fruit may dry and break viable for extended periods of time. Germination open violently (dehiscence), flinging the seed some and growth may be delayed until suitable growing distance from the mother plant. An example of a conditions occur. Having seeds of desirable plants plant using this dissemination mechanism is remain viable for many years is beneficial, but when chickpea. Still other fruits may have “wings” weed seeds remain viable for many years, it creates (samaras in ) or “umbrellas” (the parachute- a need for ongoing weed management. like pappus of dandelions) that allow them to “ride There are exceptions to the rule of extended seed the wind” to a new location. Cockleburs have a viability. The seeds of some plant species are barbed fruit that attaches itself to clothing or animal capable of growth for only a few days and then only fur, providing the seed with transportation. Small if kept constantly moist. Species of plants with short animals gather, transport, and bury nuts, not only periods of viability usually live in warm, or at least moving the seeds but planting them as well. moist, conditions and often produce seeds that Fruits are also important for human nutrition, and develop within wet, pulpy fruits. many garden plants are produced for their edible Recently purchased seed has usually gone fruits. Some fruits, such as cucumbers and , are through a certification process, meaning the picked and eaten at a botanically immature stage. germination percentage has been tested in a Others reach full maturity before being picked, laboratory and acceptable levels of seed viability meaning growth is complete and the seed is capable ensured. Older seed or seed that has not been of germination. Examples are and pumpkins. certified can be tested at home to make sure it is Seeds viable. Before testing germination, make sure the Seeds form when ovules are fertilized after seed is not dormant (see a discussion of dormancy pollination. Thus, they contain genes from both the below). female and male parents. Each seed is an A quick, simple way to test viability of most encapsulated embryo, in essence a miniature but seeds is to float the seed in a container of water. fully formed plant within a protective coat. Once the Seeds that float are usually not viable; live seeds embryo is formed, it usually goes into a state of will sink. However, the most reliable method for arrested development until the seed is separated assessing viability is a germination test. Place a from the mother plant and is exposed to proper known quantity of seeds on a moist paper towel and growing conditions. seal it in a plastic bag. After a week to 10 days, Seeds, in addition to fruits, are important sources inspect the seed to determine the percentage that has of food for . We grow many plants for their sprouted. edible seeds, including nuts, legumes, and grain. Seed storage. Due to the tendency of seed to remain viable over extended periods of time, seed Seed viability. In order for seeds to grow, the can often be stored for 1 to several years, depending embryo must be viable , or alive. Factors such as

3 - 12 BASIC BOTANY CHAPTER 3 on species and storage conditions (Table 4). Even with sandpaper or nick it with a knife. Heat under ideal conditions, however, seeds of some treatments using boiling water can also disrupt the plants (such as onions, , and ) may seed coat enough to allow germination. With this remain viable for only 1 year. Seeds of other plant method, it is important to use caution to avoid species (such as radishes, tomatoes, grains, and personal injury. Also, be sure you know the proper many grass species) may remain viable at least 6 length of treatment to avoid damaging or killing the and sometimes more than 20 years. seed. Successful seed storage requires proper Embryo dormancy is a chemical/physiological conditions. The keys to long storage are temperature condition that prevents growth, usually associated and humidity, with cool, dry conditions being best. with the balance of growth hormones in the seed. In The “rule of 90” can help you determine a suitable nature, this type of dormancy ensures that seedlings storage site. Measure the temperature and relative will emerge in the spring, rather than in the fall. The humidity of the intended storage location and add hormonal balance of the seed changes toward a the two values together. If the sum is less than 90, status favoring growth during exposure to cold, extended seed storage should be successful. Low moist soil conditions. This type of dormancy can be humidity is the most critical factor for seed storage, overcome by stratification , a process of artificially but generally, lowering either humidity or chilling seeds under moist conditions. Place the seed temperature will extend the storage period. Long- in moist potting soil in a small plastic bag and place term viability of seeds can be ensured by placing the the bag in a refrigerator for 1 to 3 months. seed in a sealed container with a desiccation gel Seed dormancy attributes and the methods packet and placing the container in a freezer. required to overcome dormancy vary widely among Seed dormancy. Some seeds, although viable plant species. Success with many plants depends on and planted under correct conditions, fail to grow. understanding dormancy characteristics and finding These seeds are exhibiting a natural survival the best ways to satisfy dormancy requirements. characteristic termed dormancy . Dormancy is an Good reference materials are available to determine adaptation of some plants to keep seeds from necessary conditions for germinating seed of germinating until conditions favor seedling survival. difficult species. Most of our common food crops and annual flowers lack dormancy, meaning the seed will grow as soon as it is planted into warm, moist soil. However, many perennial flower species (such as monkshood, Table 4. Examples of longevity and minimum , columbines, and penstemons) and most germination (percentage of live seed required to hardy shrubs and trees produce seed with some form ensure successful production). of dormancy. In these cases, dormancy must be broken before seedling establishment can be Kind Longevity Minimum germination of seed (years) (percent) successful. Bean 3 70 The most common mechanisms of dormancy are Beet 4 65 seed coat impermeability and embryo dormancy . Carrot 3 55 Seed coat dormancy is caused by the presence of a Corn, sweet 2 75 thick, hard seed coat that is impermeable to water. Cucumber 5 80 In nature, weathering, soil abrasion, the action of or passage through the digestive Lettuce 1 80 tract of an animal can soften the seed covering, thus Muskmelon 5 75 allowing the seed to take up water and begin Pea 3 80 growing. Pumpkin 4 75 Radish 4 75 For garden production, an artificial method Spinach 3 60 known as scarification can be used to break or soften the seed coat. The simplest scarification Squash 4 75 method is mechanical; simply scratch the seed coat 4 70 *Source: http://www.ext.colostate.edu/Pubs/Garden/07221.html

CHAPTER 3 BASIC BOTANY 3 - 13 PLANT DEVELOPMENT New growth on all plants develops from localized —specific regions of rapidly dividing Plants go through definable stages of life, cells. Meristematic tissues within any plant include beginning with germination (sprouting) and ending those providing both apical and lateral growth. The with senescence and death. Some annuals complete apical meristems are found at the tips of stems and this entire process within a few months, while some roots and produce cells resulting in longer stems and tree species live for thousands of years. branches. Lateral meristems are located along the Seed germination interior of the stem and roots and serve to increase the diameter of stems, trunks, branches, and roots. Plant development begins with the germination of Lateral meristems are especially important in the a seed. First, the seed swells as it absorbs water. The expansion (increase in diameter) of woody tissues in first root ( ) emerges from the seed coat and radicle trees and shrubs. grows downward. In proper conditions, the new roots and root hairs grow down Grass plants have a unique form of apical into the soil to anchor the plant and acquire water called the intercalary meristem , located and minerals. Meanwhile, the shoot portion of the at the base of the leaves. Intercalary meristem cells stem emerges from the seed and begins extending divide and produce new growth from the leaf base, toward the soil surface. giving grasses the unique ability to regrow after mowing or . Scalping grass with a mower During germination and seedling establishment, ( to a very short length) or overgrazing may young plants are vulnerable to damage from damage or remove this meristem and cause a bald conditions that may not damage an established (no grass) in the lawn or pasture. plant. Lack of moisture, excessive heat or cold, pests, and diseases can all kill or seriously damage Reproductive growth stage an emerging seedling. For example, an established Upon achieving adequate size and storing plant may be hardy to -25°F, while a tender young sufficient energy, flowering plants go through a plant of the same species may be hardy to only process of physiological change that favors the 32°F. As the fragile new shoot moves up through the development of reproductive organs at the expense soil, it may also be damaged by the inability to of vegetative growth. Among angiosperms, this penetrate heavy or compacted soil. means producing flowers and fruits. Once flowering Because of this extreme vulnerability, is induced, particularly with annuals and herbaceous germinating seedlings require that we pay careful perennials, leaf growth usually slows and the plants attention to cultural details. We must adequately become more fibrous and stout. For annuals, the prepare the soil, plant seed to the proper depth, reproductive process occurs only once before the maintain proper moisture conditions, minimize plant senesces and dies. For long-lived perennial exposure to pests, and control temperature as much and woody species, the reproductive cycle may be as possible. repeated many times during the life span of a single plant. Vegetative growth stage Flowering is influenced by many external and Once a seedling is established, the size and internal factors, including genetics, plant mass, plant complexity of the plant increases as the first true health, hormone balance, temperature, and day leaves are formed. Stems elongate and produce length. Cold or warm temperatures at a specific additional leaves. The leaf surface increases, thereby stage of growth can trigger the flowering process. enhancing the plant’s ability to capture and utilize For example, consistent cold weather will cause light. During this stage of development, growth is young broccoli plants to bloom early instead of rapid and plant parts tend to be large and succulent. growing large heads. Another important trigger for Also, the growing plant begins to some plants is the length of the light period. Onions, characteristic branching and rooting patterns. For for example, require increasingly long early summer example, will produce -like leaves and a days to trigger bulb growth. These triggering long taproot, while blue fescue will develop long, mechanisms ensure that the plants produce flowers narrow leaves from a crown and a dense, fibrous root system.

3 - 14 BASIC BOTANY CHAPTER 3 during the optimal time of the year so that flowering Coombes, A. J. 1994. Dictionary of Plant Names . and fruit development can be unhindered. Timber Press, Portland, OR. During fruit set—the next phase of reproductive Cooperative Extension, College of Agriculture, The growth—the ovary develops into a fruit with seed. University of Arizona. 1998. “Botany: Plant Parts Fruit and seed development takes a great deal of and Function.” In Arizona Master Gardener energy. For this reason, it may be beneficial to Manual . http://ag.arizona.edu/pubs/garden prevent fruit from developing when plants are just /mg/botany/.html getting established. Dead-heading is another Durant, M. 1983. example of preventing fruit development, in this Who Named the Daisy? Who case to promote more flowering. Any stress that Named the Rose? A Roving Dictionary of North . Congdon & Weed, Inc., reduces photosynthesis—drought, nutrient American Wild Flowers , NY. deficiencies, insects, or diseases—will negatively affect fruit development. Ham, D. L., and L. R. Nelson. 1998. Newly Planted Senescence Trees: Strategies for Survival . Clemson Extension Leaflet 17. http://www.clemson.edu For annuals and biennials, death is the next and /extfor/urban_tree_care/forlf17.htm final stage following fruit development. Senescence is a series of steps that lead to the death of a plant. Hartman, H. T., A. M. Kofranek, V. E. Rubatzky, The plant ceases to metabolize, and nutrients are and W. J. Flocker. 1988. Plant Science . 2nd ed. moved from the vegetative structures to the fruits. Prentice-Hall, Inc., Englewood Cliffs, NJ. Perennial plants do not die after fruit production. Jensen, W. A., and F. G. Salisbury. 1972. Botany: An On herbaceous perennials, however, fruiting may Ecological Approach . Wadsworth Publishing Co., signal an annual dieback of foliage. In woody Belmont, CA. species, fruiting may or may not be associated with Kroening, M., and D. Trinklein. 2007. “Plants and fall leaf drop and annual dormancy. their Environment.” In Missouri Master For all plants, the stages of development Gardener Core Manual . University of Missouri associated with maturation and senescence are Extension. http://extension.missouri.edu accompanied by a lack of response to outside /publications/DisplayPub.aspx?P=mg2 influences. In other words, the plants are Raven, P. H., R. F. Evert, and S. E. Eichhorn. 1992. programmed to naturally decline, and no inputs of Biology of Plants . 5th ed. Wort/Worth Publishers, nutrients, moisture, or any form of tender loving New York, NY. care will extend their life. During this stage of development, plants also become more prone to Robinson, E. R. 1939. New Pronouncing Dictionary diseases and insect feeding. Luckily, pests do little of Plant Names . Florists’ Publishing Co., lasting damage to plants at this stage of their lives, Chicago, IL. and efforts to control pest issues during senescence Wilkins, M. 1988. Plantwatching . Facts on File are usually unwarranted. Publications, New York, NY.

FURTHER READING AND RESOURCES Woodland, D. H. 1991. Contemporary Plant . Prentice Hall, Englewood Cliffs, NJ. American Nurseryman Publishing Co. Pronouncing Dictionary of Plant Names. 2006. American Nurseryman Publishing Co., Chicago, IL Barden, J. A., R. G. Halfacre, and D. J. Parrish. 1987. Plant Science . McGraw-Hill, Inc., New York, NY. Capon, B. 1990. Botany for Gardeners . Timber Press, Portland, OR.

Published 1993. Revised 2012.

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