Horticulture 101

Horticulture 101 (Marianne Ophardt) Slide 1 Hi, this is Marianne Ophardt and today we‟re going to be talking about Horticulture 101. Horticulture is a topic that most gardeners might not think would be very interesting, but it lays the basis for a lot of things we do in gardening. So let‟s get started. Slide 2 We‟re all taxonomists. We like to name and classify things. Early humans classified plants by their use, such as if they were used for medicines, seasoning or dye. Slide 3 We also like common names. Common names are easier to pronounce and to remember. But common names can be confusing. For example, Chamaecyparis lawsoniana, also known as Port Orford cedar or Lawson‟s cypress, is neither a true cedar or a cypress. Juniperus viginiana, also known as red cedar in the east, is not a cedar. Thuja plicata, also known as red cedar in the west, is not a cedar. When we use common names properly in writing, it‟s not capitalized unless it‟s a proper noun, such as something like Forsythia, which comes from the name Forsyth. Slide 4 We need to thank Carl von Linne. Carl von Linne was a Swedish doctor who developed the hierarchy system of scientific binomial names for plants and animals in 1753. He even changed his own name to Carolus Linnaeus to give himself a scientific binomial name. He did groupings that were based on reproductive structures. His hierarchal system created order out of chaos. If you had someone in one country talking about a plant using a common name, they might not be talking about the same plant because in another country it might have a different common name. Thus the binomial naming system for plants and animals really has made things a lot easier in talking about plants to gardeners around the world. Plant names are reviewed by International Commission for the Nomenclature of Cultivated Plants. Often scientists find some relationships that are different than they first thought and names of plants change because they find some plants are more closely related to others than they thought. Slide 5 Gardeners are usually only interested in perhaps the family, genus, and species of a plant. But there‟s more when we talk about the taxonomy hierarchy. For example, the tomato, a common garden plant. It‟s in the plant kingdom. It‟s in the division of flower-bearing plants. It also is in a Page 1 of 15 special class and order before we get all the way down to family. So we‟re mostly going to talk about plants from the family, genus, and species. Slide 6 A family is a group of plants having a number of similar characteristics, especially in their reproductive structures. A family can be composed of one or more genera. Slide 7 For example, the Rose family, the Rosaceae family. One member is Rosa. That‟s the genus. Rosa – rose. Rubus, another genus, is raspberry. Prunus includes cherry, plum, apricot, peach, and almond. The Malus genus includes apple and crabapple. Cotoneaster includes cotoneaster. Fragaria – strawberry. Chaenomeles – flowering quince. But we‟re not done yet, there‟s more. Slide 8 Crataegus – Hawthorn Potentilla – Potentilla Amelanchier – Serviceberry (or some people know it as shadbush) Sorbus – Mountain Ash Spiraea – Spiraea Pyracantha – Pyracantha and Photinia – Photinia These are all members of the rose family but different genera. If you look at the flowers on these you‟ll find that there are similarities in the flowers and in the fruiting structures. Slide 9 Next is the genus. The genus is a group of plants more like each other than any other with similar structure, appearance, and chromosome makeup. Inter-grafting sometimes is possible between the different genera. Occasional hybrids from breeding may occur, too, but only occasionally. Slide 10 Next is species. Species is the specific division of a genus. The plants are morphologically similar within the genus and interbreeding is possible to form hybrids. Slide 11 Next, even more closely related is a variety. We often as gardeners refer to a variety but we are Page 2 of 15 using it wrongly. Variety is a fairly consistent naturally occurring variation of a species and when we‟re writing the plant name it‟s preceded by “var.” indicating variety. Slide 12 When we write out plant names – if we want to do it in the proper form – the genus is always capitalized. And if you‟re writing it or typing it, it‟s in italics or underlined. The species is usually lowercase (with the exception of proper nouns) and it‟s in italics or underlined. Variety is in lowercase and it‟s also in italics or underlined but preceded by “var.” indicating variety. Slide 13 I would imagine you‟d like some examples of that. Here we have an example of the mustard family: Brassica oleracea var. botrytis (Cauliflower) the genus is Brassica, the oleracia is the species, and the variety is botrytis. Next we have Brassica oleracea var. capitata (which is Cabbage) So the genus again is Brassica. The species is oleracia and the variety is capitata and that means “head” in Latin. Brassica oleracea var. italica (is Broccoli) Brassica oleracea var. gemmifera (is Brussel Sprouts) You can see that all of these are in the same genus and species but each is a different variety. What we often refer to as variety such as a variety of cauliflower or cabbage is actually the cultivar. Slide 14 A cultivar or cultivated variety is maintained by cultivation. It may be the result of chance sexual reproduction where it was selected because of good or interesting traits that it had. It may be the result of a mutation or bud sport that appealed to someone as interesting or different. Or it may be the result of selective breeding by plant breeders. Slide 15 When we see a cultivar or cultivated variety name in print, the name may be in Latin or English, capitalized, and not underlined. It‟s put in single quote marks or preceded by cv. – meaning cultivated variety. One example would be „Big Boy‟ or „Better Boy‟ tomatoes – both cultivars or cultivated varieties. Slide 16 Gardeners need to know that names keep changing. Scientists continue to study evolutionary relationships. New species are discovered. Studies reveal closer or different relationships than first thought. For example, the Brassicaceae family used to be the Cruciferae family. The Asteraceae family used to be the Compositae family. Scientists have found that these are more Page 3 of 15 closely related than they thought and so they renamed the families. Slide 17 A hybrid is the result of sexual reproduction or a cross between parents that differ in one or more genes. The term hybrid can be used to describe a cross between two different species such as Clematis x jackmanii, which is a hybrid that resulted from a cross between two different species: Clematis languinosa and Clematis viticella. The term hybrid can also be used to refer to a cross between two different varieties. An F1 hybrid is the result of a cross between two inbred lines. Slide 18 Inbred lines are created by plant breeders by self-pollinating closely related plants that would normally cross-pollinate. The plant breeders will usually do this for ten generations to create an inbred line. Inbreeding in plants results in death and sterility of some offspring and weaknesses in the line, such as reduced growth and yield. But the purpose is to get an inbred line so that you can get an F1 hybrid. Slide 19 An F1 hybrid is the result of a cross between two inbred lines. The result is offspring that are very uniform. These offspring may or may not have a higher yield and earlier maturity. Hybrid corn was first introduced in the 1930s. It was an F1 hybrid and the corn was higher yield and earlier maturing and very uniform, which definitely was an advantage for commercial agriculture and the farmers who were growing the hybrid corn. Since then, more and more vegetable and flower hybrids have been bred for the commercial and home garden markets. Slide 20 Break Time Slide 21 Now let‟s move on to the different parts of the plant. First we‟ll look at the roots. What‟s the function of roots? One of their primary functions is the absorption of water and nutrients for the plant but they also anchor plants to the soil. They provide storage of carbohydrates or energy reserves for the plant and they‟re a site of synthesis for new compounds and for new cells. When we look at the structure of the root, at the very tip is the root cap. This is a protective layer that protects the meristem zone beneath it. The meristem is where new cells are being formed by cells dividing. After the cells are produced, then they elongate and become larger and then start to differentiate or mature. You‟ll notice in the diagram the root hairs. The root hairs are some differentiated cells that are elongated and have a larger surface area. This provides for the root by allowing more water absorption and nutrient uptake. As the cells mature, they become different types of cells that have different functions. One of those is vascular tissue, which is basically the plumbing of the Page 4 of 15 plant and we‟ll talk more about that soon. We have to remember that roots require oxygen and carbohydrates for growth. They‟re a living part of the plant. If we deny them oxygen or food they won‟t function properly.

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