LANT LOVERS are usually game to try something new. But how Design Lessons P do we know a won’t need constant weeding and feeding, be candy, or, as temperatures soar, wimp out in the heat? Many experts claim that from Mother Nature you don’t really know how to grow a plant until you’ve killed it at least three times. If we understand the survival strategies that allow a plant to adapt to conditions in its native habitat, however, we can choose that will beat those odds by a long shot. There’s more to sur- vival of the fittest than meets the eye, but we can tell a lot just by looking. EVOLVING DIVERSITY Plants co-evolved with other plants— along with soil microorganisms, insects, birds, and other wildlife—in response to environmental forces. To survive, each

Understanding how plants adapt to their ecosystems can give you an edge when designing your garden. to 30-foot understory tree of moisture-rich deciduous forests, with large, thin, heart- shaped, matte leaves that soak up the sun. At the hot, dry, southern end of the ’ ARTICLE AND PHOTOGRAPHS range, drought-tolerant Mexican redbud BY KAREN BUSSOLINI (C. canadensis var. mexicana) is short and shrubby with very small, glossy, wavy-edged leaves. redbud (C. canadensis var. tex- species had to develop ways to make the ensis), adapted to conditions between these most of available resources—water, light, extremes, is intermediate in every regard. nutrients, space, pollinators, etc.—to thrive. And they had to avoid being eaten THE BIG PICTURE by something up the food chain, at least When you look at a wild landscape, you long enough to reproduce. can see patterns in the vegetation. Plants If a trait consistently allows an individ- indicate where the water is; where soil ual to better survive in its environment is deeper, richer, or rockier; or where and out-reproduce its competitors, off- there is some shade. Learning to read the spring with the inherited trait will pro- native landscape gives us lessons worth liferate, generation after generation. This taking home and clues for smart selec- process of natural selection within species tions of plants from anywhere. The more enables organisms to claim specialized we emulate the structure, patterns, and Top: The ecosystem of the eastern deciduous forest is made of layers of vegetation, with shorter, niches and develop mutually beneficial plant composition of local natural plant more shade-tolerant plants growing under taller, sun-loving trees. Above: In this neighborhood, relationships with other species. communities, the more successful and the owner of the garden in the foreground has taken cues from the desert environment and planted Subpopulations of a species that evolve sustainable our own yards will be. cacti and other succulents instead of the water-hungry turf growing in the yard across the street. genetically distinct, heritable adaptations in In the Sonoran Desert, wide-reaching response to local conditions are called eco- shallow root systems, covered with hairs cent water and can weigh tons. Water from But they grow in close association with and mesquite are prominent members of the plant community in the Sonoran Desert. types. Redbud trees are a good example of that can harvest up to 200 gallons of wa- short, intense desert storms runs off fast, so mesquite (Prosopis spp.), desert ironwood The ’s shallow, far-reaching root system and the mesquite’s deeper roots allow them to this spectrum of change. In the north, the ter in a rainfall, anchor the saguaro cactus. saguaros slurp it up, store it in their tissues (Olneya tesota), palo verde (Parkinsonia grow in close proximity to each other and share in the desert’s meager rainfall. eastern redbud (Cercis canadensis), is a 15- Saguaros (Carnegiea gigantea) are 90 per- and keep their distance from each other. spp.), and other shrubs whose roots are

24 the American Gardener January / February 2020 25 tect them from sunscald, moisture loss, insects, and other herbivores. Leaf size, shape, color, and arrangement give a lot of clues about where a plant grows. Most desert plants have small leaves. When temperatures soar, the less surface area exposed to sun and drying winds, the more protection from overheating and desiccation. Many fine-leafed pea-family plants, including Acacia, Cassia, Lespede- za, Dalea and Lupinus species, are adapt- ed to dry areas. Relatives native to more temperate prairies and woodland edges, such as false indigo (Baptisia australis), can afford to have larger leaves. Even outside the desert, small leaves are usually a good indication of relative heat and/or drought tolerance and/or need for well-drained soils. If you compare narrow- leafed mountain mint (Pycnanthemum tenuifolium), a perennial found in fairly

Resources Botany for Gardeners by Brian Capon. Timber Press, Portland, OR, 2010. Ecology for Gardeners by Steven B. Carroll and Steven D. Salt. Timber Press, Portland, OR, 2004. Plant Survival by Brian Capon. Timber Press, Portland, OR, 2009. In drought-prone environments, spacing plants widely allows each more equitable access to limited available water. In this garden in , pools of pineleaf penstemon bloom among cacti and other plants. The penstemon has tiny, pine-needlelike leaves that are adapted to minimize water loss. dry, upland soils from to Texas, able to find deeper underground reserves. watering in other hot, dry places. Sa- layer decomposes, building soil, recycling with wider-leafed P. muticum, a meadow- These feathery-leafed thorny legumes guaros are endemic only in the Sonoran nutrients that, with the aid of a robust com- dweller, it’s not hard to guess which one to are nurse plants—their canopies form a Desert, but other big desert succulents— munity of macro- and microorganisms, be- plant in fertile moist garden soils and which protective microhabitat essential for the including ocotillo, , dasylirions, come available to roots of forest plants. would favor a dry spot with good drainage. germination and survival of saguaros and agaves, and cacti—benefit from wide Mature trees shade many neighborhoods The same goes for fine-textured pineleaf many other plants. They moderate tem- spacing and similar plant associations. across the continent. Yards are all too often milkweed ( linaria) as compared peratures, add structural diversity, im- Xeric places have lots of diversity but can carpeted with labor and resource-guzzling with swamp milkweed (A. incarnata), prove soil fertility with their leaf litter, and only support so many plants. The lush lawns, with the middle layers missing. which has more substantial leaves. are crucial to untold complex plant-in- look requires water and soil high in or- Homeowners who plant regionally During the growing season, water-rich sect-wildlife interactions. ganic matter. appropriate understory trees, shrubs, and landscapes are overwhelmingly green, but Between these islands, smaller The eastern deciduous forest provides ground layer plants can let the layers do dry places have a more muted palette. The succulents, grasses, resinous small- or a model for sustainable landscaping where the work. Filling all the niches doesn’t coloration of grayish and silvery-looking leathery-leafed shrubs, and forbs thin out trees dominate. With more rainfall, nutri- leave much room—or light—for weeds plants comes from protective adaptations to reveal patches of seemingly barren soil ents, and moderate temperatures, plants can and reduces the need for mulching; letting that give leaves a shimmering, ghostly look. in less hospitable areas. Ephemeral plants grow larger and closer. Forest structure is leaves decompose in place greatly reduces These plants thrive in forbidding condi- emerge from those bare places after winter layered. Tall canopy trees shade understory the need to apply water and fertilizer. Even tions—deserts, windswept plains and rocky rains. Many are annuals. Individual plants trees, which shade understory shrubs that small trees moderate climate and can foster cliffs, salt-sprayed coastlines, and frigid germinate, bloom (spectacularly under top ground layer plants. Canopy trees grab self-sustaining communities of plants while mountaintops—because they evolved in ideal conditions), set seed, and die; but the most of the light, so understory plants need welcoming wildlife. response to these challenging environments species live on, dormant in seed form until to get along with less. Each leafy layer breaks by becoming silver. sufficient rains return. the force of rain, limiting soil erosion and LOOKING AT LEAVES In deciduous forests, understory plants have adapted to maximize their access to sunlight on the Downy silver leaves are covered with This particular ecosystem gives good runoff. Each autumn, year after year, leaves While leaves need to collect sunlight for shady forest floor. The layered leaf arrangement of maidenhair fern, top, allows light to fall on its fine, light-colored hairs that shade otherwise guidance for landscaping and reducing fall to earth. This moisture-absorbing leaf photosynthesis, many adaptations pro- lower branches; Canada ginger, bottom, has large dark leaves held horizontally to soak up light. green leaves and/or stems. These hairs reflect

26 the American Gardener January / February 2020 27 ern cool-season bunchgrass, are especial- Bulbs, corms, rhizomes, and tubers are violets, are a sure sign of spring. Colonies ly valuable in low-water gardens. Several swollen underground organs that allow a of bluebells (Mertensia virginica) intensely blue selections of native grasses plant to store water and nutrients and wait turn moist woods and forested floodplains are popular. These include little bluestem out seasons of drought, excessive heat or throughout the east and Midwest into a sea ‘The Blues’ and ‘Standing Ova- cold. Seeds are semi-dormant embryonic of blue with clusters of bell-shaped . tion’, blue fescue selections like ‘Siskiyou plants programmed to germinate when They’re a welcome sight in the spring gar- Blue’, and switchgrasses (Panicum virga- conditions are favorable. A seed that is den, where they enthusiastically self-sow, tum) ‘Heavy Metal’ and ‘Prairie Sky’. fooled by a sprinkle of rain in the desert or but not so pretty when foliage dies back In the woodland, some plants that one warm winter day is unlikely to survive. unless followed by plants tall enough to emerge before overhead trees leaf out, or Deciduous plants that drop their cover the mess. Virginia bluebells are ideal grow on exposed woodland edges or rocky leaves in fall are slowing down to weath- for naturalizing in shady damp areas with outcrops, benefit from silvery variegation. er low temperatures and light. Palo verde ostrich ferns (Matteuccia strupthiopteris), Populations of alumroots (Heuchera spp.) can be variably mottled in silver and gray. Native gingers may display beautiful silvery veining patterns. Noteworthy selections of southeastern Hexastylis species, commonly sold as Asarum shuttleworthii var. shuttle- worthii ‘Carolina Silver’, A. arifolia ‘Silver Spreader’, and A. lewisii ‘Carolina Carpet’, will light up a woodland garden. Light is the key limiting factor for understory plants. Leaves under those The contrasting leaf shapes of swamp milkweed, above left, and pineleaf milkweed, above right, reflect their adaptations to very different regional sun-hogging canopy trees must take up climate conditions—one being temperate and moist while the other is hot with strong sun and extended periods of drought. the sun’s energy early, develop enhanced light-gathering ability or make do with sunlight and cool the leaf, keeping moisture coatings protect the leaf from extremes of Plants from this blue end of the sil- less. Thinner, broader leaves collect more close to its surface—and have little appeal to heat, cold, drought, wind, salt spray, and ver spectrum blend right into dry land- light for photosynthesis. Leaves of the leaf-munching animals. Tender silver pony- sun. And like them, they’re only as silver scapes and provide lovely color accents in striped maple (Acer pensylvanicum), a foot (Dichondra argentea) makes an incan- as they need to be. Intensity of color indi- greener gardens. The silvery-blue-hued small understory tree of cool moist woods descent creeping groundcover in warmer cates amount of protection; more benign grasses such as widely distributed little throughout the East, are almost twice parts of Texas to . Sand sage locations or times of year don’t compel the bluestem (Schizachyrium scoparium) and as big (and less glossy) as those of sugar (Artemesia filifolia) found on dunes and san- plant to expend energy protecting itself. blue fescue (Festuca idahoensis), a west- maples overhead. Shadblow (Amelanchier dy soil in Texas through , with- spp.) trees bloom and leaf out early, before stands extremes of heat, cold, and wind, yet canopy trees cast their shade. Dark-needled tolerates decent garden soil. Drive across the hemlocks (Tsuga canadensis, T. caroliniana), open high plains on a moonlit night where require a tiny fraction of the light needed by prairie sagebrush (A. frigida) or Great Basin other trees. The broad leaves of evergreen In woodland gardens, early spring is a key time for understory plants like spicebush (Lindera sage (A. tridentata) dominate and the entire rhododendrons (Rhododendron spp.) and benzoin), center, and ramps (Allium tricoccum), foreground, to shine before canopy trees leaf out. landscape glows silver. mountain laurels ( latifolia) capture Some downy silvers have the coloration the sun’s energy year round. defoliates during extended drought in- which emerge as bluebells go dormant and but not the fuzzy appearance. Quaking On the forest floor, the amount and the stead, continuing photosynthesis in benefit from the mulch of dead foliage. aspen (Populus tremuloides), whose leaves wavelengths of light change as the canopy green bark on trunk and branches. Oco- We can learn much by observing natural flicker silver when the wind reveals their un- closes in. Many plants arrange their leaves tillo (Fouquieria splendens) is a woody landscapes, even at 60 mph from our cars. dersides, and epiphytic “air plants” such as flat to the sun for maximum benefit. Others succulent with vicious thorns and no But better yet, take a closer look on a leisure- Spanish moss and ball moss (Tillandsia spp.) utilize normally unusable parts of the light apparent leaves—until it rains, when ly hike or visit a botanical garden or nature have scales comprised of collapsed hairs. spectrum or respond to changes in light by clusters of small oval leaves can emerge center to get a feel for the characteristics of Other silvers are covered with a waxy initiating or suspending growth. from dormant buds within 48 hours of the plants that live there. With an educated layer, something like the bloom on a plum, a downpour. eye, we’ll recognize—and plant—survivors or a mealy coating. Rub the needles of a DORMANCY—TIMING IS EVERYTHING Woodland spring ephemerals are actu- when we see them. m blue spruce (Picea pungens var. glauca), In the plant world, the balance between in- ally long-lived, colony-forming perennials. from cold, windy mountainous regions, vesting energy in growth or protection tips They emerge and bloom early, quickly col- Karen Bussolini is a garden photographer, or leaves of the prairie plant known as rat- toward protection in resource-poor envi- lect and store a season’s energy in roots or writer, speaker and eco-friendly garden tlesnake master (Eryngium yuccifolium), ronments. When the going gets too tough bulbs, then go dormant, to be succeeded by coach based in . Parts of this or Agave parryi, a desert-dweller, and the for growing, some plants go dormant, ground-layer plants that require less light. article originally appeared in Wildflower, coating comes right off, revealing a green Downy silver hairs protect the green leaves of Artemisia stelleriana from intense sun and other temporarily suspending active growth to Erythronium species, commonly known the publication of the Lady Bird Johnson leaf. Like the hairs on downy silvers, these inhospitable conditions, such as those found on this windswept Nantucket sand dune. conserve energy. as trout lilies, adder’s tongue or dogtooth Wildflower Center.

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