2.1: Plant Habitats
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- Identify plants used in all segments of horticulture.
The horticultural use of plants for decoration, food, medicine, and materials spans the history of human development on earth. While early European explorers to North America described the new world as untouched wilderness, generations of Indigenous residents used plants for decoration and ritual and managed growing conditions for food for thousands of years. The relationship between people, plants, and the environment on the Pacific coast of North America is described at this link to the Garry oak ecosystem [New Tab].
The early European plant explorer, Archibald Menzies has been credited as the first discoverer, describer, and collector of a number of plants whose provenance is the Pacific Northwest. Provenance refers to the populations of plants that occur naturally in local regions. For example, Pseudotsuga menziesii (Douglas fir) and Arbutus menziesii (Pacific madrone) both occur naturally in the Pacific Northwest. A plant’s nativity or provenance can be determined either geographically or politically. Acer saccharum (sugar maple), is native to central eastern North America, in other words, a Canadian native, but not a Pacific Northwest native. Similarly, Artemisia tridentata (big sagebrush) and Rhusglabra (smooth sumac) are native to interior British Columbia, but only to the dry interior valleys, not to the coast.
Plants that occur naturally in a place are considered native or indigenous to a place. Native plants have undergone genetic adaptations that have allowed them to evolve within the physical, chemical, and biological conditions of local ecosystems. As such, they function as part of a biodiverse community of organisms that includes plants, animals, and microorganisms adapted to local environmental conditions.
In North America, an indigenous designation is usually applied to plants that were present before first contact with Europeans. Thus, Plantago spp. (plantains), although widespread here, are not considered native since they were brought here as a result of immigration by early European settlers. However, the influences of climate change and globalization will likely redefine what it means to be indigenous.
Native gardening with indigenous plants that are appropriate to the conditions and geography of a given area can simulate the biodiversity of a natural habitat. Native plant gardens locally frequently include plants that are not native to the Lower Mainland of British Columbia, but also include plants native to other parts of the Pacific Northwest. For instance, Quercusgarryana (Garry oak), also discovered and described by Archibald Menzies, is now grown in gardens in the Lower Mainland, but is only found naturally in rain shadow climates, such as on southern Vancouver Island.
While not all native plants may be garden worthy for ornamental impact, those chosen from the regional locality of a garden will often blend appropriately and will be among the best adapted to local moisture, soil, and climatic conditions. Although native plants are not immune to pest and disease problems, the majority of locally native plants seem to attract fewer problems than many exotics do. Efforts to restore natural habitats using provenance-specific plants grown from locally sourced seed perform better than non-natives when established in these areas. However, changing climate patterns and the impacts of urbanization will likely have consequences for plant provenance.
Natural habitats provide the resources that enable indigenous plants to persist and thrive in existing growing conditions. Examples of natural habitats commonly used as horticultural garden themes include alpine, woodland, Mediterranean, and bog. The growth characteristics of plants native to these habitats have been shaped by differences in elevation, temperature range, precipitation, soil types and geology, and biological and chemical factors. Over time, indigenous species successfully adapted to the habitat conditions by developing specialized features for survival. Some features associated with alpine, woodland, Mediterranean, and bog plants are described below. Additional information about how evolution and natural habitats have influenced plant adaptations is available at this link to the Missouri Botanical Garden [New Tab].
True alpine plants are well adapted to the harsh environments of high elevations. Above tree line, low temperatures, high sunlight, constant wind, dryness, and a short growing season are typical. Plant adaptations include growth low to the ground, a compact cushion or mat habit, and thick, waxy evergreen or pubescent (hairy), or curly leaves. Alpines, such as Campanula spp. (bell flower) flower in late spring and early summer and may have deep or extensive roots or below ground storage organs to persist in thin, low nutrient mountain soils. Although well adapted for extreme temperatures, alpine plants are typically intolerant of constant wetness around the roots and warm and humid summer conditions. Information about these specialized plants is available at this link to Adaptations to Alpine Plants [New Tab].
Woodland understory plants
The temperate woodland habitat is characterized by distinct growing seasons, a dormant period, relatively consistent precipitation, and rich soils. Trees dominate this habitat forming an overhead canopy that shades and cools the understory and forest floor to varying degrees. Woodland understory plants include layers of woody shrubs and herbaceous plants that are adapted in size, form, shade tolerance, and slow growth or dormancy when light and water are limited. Understory plants such as Hydrangea quercifolia (oakleaf hydrangea) flower in late winter to early summer, before the leaves of deciduous shade trees fully emerge. Depending on the amount of light available, some understory plants have distinctive leaf color and patterns of ornamental interest in gardens. Examples of understory plants for garden use are shown at this link to Creative Woodland Garden Ideas [New Tab].
Mediterranean plants, such as Cotinus coggygria (smoke bush) and Lavandula spp. (lavender)are adapted to short, mild, and wet winters and long, warm, and dry summers. Some are short, dense, and shrubby evergreens that are suited to well drained soils, drought, and fire. Leaves may be leathery or reduced in size, and aromatic with thick, waxy or hairy coverings to reduce water loss, and bluish-grey (glaucous) or light in color to reflect excessive light. Some examples of naturally occurring vegetation are listed at this link to the Mediterranean climate Wikipedia [New Tab].
Bogs and freshwater habitats are typically oxygen and nutrient poor with acidic pH conditions. Quercus palustris (pin oak) is an example of a tree that naturally grows in these conditions. Bog plants are adapted to growing in standing water while marginal plants such as Irissiberica (Siberian iris) and Typha spp. (cattail) thrive in waterlogged soils and shallow waters with short term dryness. Some bog and marginal plants such as Juncus effusus ‘Spiralis’ have striking foliage and make good choices for planting areas with limited or poor drainage. Information about the bog habitat is available at this link to Plants of the Bog [New Tab].
- en.Wikipedia.org/wiki/Mediterranean_climate#Mediterranean_biome ↵