Overview of Plant Physical Characteristics by Region

they would not resist, unlike the stiffer leaves of a horse chestnut or oak. The aesthetic, physical, and seasonal attributes of plants are endless. Choosing the right plant and combination of plants is part of the art of a landscape architect.

Plants that are native to particular regions are a product of their environment. Their physical characteristics allow them to adapt to the climate, soil, and other environmental conditions of the region. One way to discuss plant species variations is by their biome. Biomes are defined as the world’s major communities or ecological areas classified according to the predominant vegetation and are characterized by climate, soil, and other particular environmental conditions that support organisms (in our case, plant species) that have adapted to these particular environments. For example, plants with small leaves and gray or light-green coloration are characteristic of arid regions while plants with large, green and dark green coloration are found in temperate or sub-tropical areas. We will briefly review the general differences one might anticipate in very broad terms by major regions.

Tropical: The tropical regions of the Earth have the greatest diversity of plant species. This diversity is also expressed in their physical characteristics. Tropical plants are known to have large leaves with great shape variation such as broad leaves and palmlike leaf structures. Plant height varies greatly, from some of the tallest species on Earth, graduating down to smaller plants found on the forest floor. Tropical rainforests are found in a broad band close to the equator. Tropical plants are typically prolific fruit and flower producers of great variety. Tropical plants are found in regions with a highly varied annual rainfall (50–260 inches or 20–660 cm), high humidity, warm annual temperatures (70–90º F or 21–32ºC), and surprisingly poor, thin soils.1 The tropical plants produce a broad spectrum of color in the form of flowers and fruit as well as a wide range of leaf sizes and shapes. Leaf colors range across nearly the full spectrum of the rainbow. Many species have glossy leaf surfaces, and others have multiple coloration, including reds and magenta and shades of white. For landscape architects working in tropical and sub-tropical regions, the plant palette is extensive and can be overwhelming in terms of the choices possible. The possibilities of creating landscape designs are similar to an artist having nearly infinite options of color to choose from.

Plant form, color, leaf size and shape, and other physical variations can be combined to create spectacular and highly nuanced landscape planting designs. Working with a tropical planting palette is not for the timid designer and it can be a daunting challenge, given the great variety of plant species found in tropical regions. Temperate: Plants in temperate regions such as North America,

Europe, and Asia are found between the tropical and polar regions. As the term suggests, temperatures in these regions tend to be moderate, and while they do experience freezing or hot

temperatures, they are not extremely cold or warm for long periods of time. Annual rainfall is generally higher in temperate regions than in polar regions but not as high as in tropical areas.

Plant species in the region include both deciduous and evergreen trees, shrubs, perennials, grasses, and herbs. Fall foliage colors can be brilliant and spectacularly showy, including yellow, orange, red, and burgundy-like hues. Foliage types include evergreen and deciduous, conifer, broad-leaf, and grasses. The presence of fruit and flowers ranges from showy and colorful to insignificant. Planting designs in temperate regions have the possibility of achieving multi-layered effects with an over-story or canopy of tall trees to a variety of plants filling in the under-story or mid-range heights down to ground level with woody and herbaceous plants. Desert: Deserts are regions that are arid with low annual rainfall, although with a degree of variation from 1.5 cm or less than an inch to 25 cm or 19–20 inches per year. The term arid can apply to both desert and polar regions as both have low annual rainfall. Deserts can be classified into many sub-categories from extremely hot climates (the Sahara) to cold deserts found in the

Arctic and Antarctica. For the purposes of landscape architecture, the desert plants that are most commonly used are found in the less extreme arid regions such as the American Southwest and moderate deserts in South America and Africa (found along the ocean coast). Chaparral and high desert regions also belong to the arid region landscape. Plant species in this category tend toward smaller leaf size, fleshy in nature as a water conservation strategy, or thin and small to cause less water loss through evapotranspiration. The physical color of these plants (leaf and branching) falls in the range of gray and lighter hues of green. Gray contributes to a plant’s ability to cut down water loss due to the process of evapotranspiration. The open branching quality of arid trees and shrubs is a prominent physical feature of desert plants and it is this quality that makes these plants selected to achieve a dramatic sculptural effect. Desert plants can also be selected for their showy seasonal flower and fruit characteristics. In some species their display of color can be stunning. Arctic: Arctic or Antarctic, these opposite polar regions both experience sustained cold, and below freezing temperatures with low annual rainfall. Soils tend to be less developed with a thin “A” soil horizon (of less than ½ to 1 inch or 1.25–2.5 cm) with gravelly or rock sub-soil. Generally the ground surface is covered in a thick mat of sphagnum moss providing insulation for the permafrost often found below the organic layer. Tree species include deciduous or conifer species. Shrubs are generally deciduous as well. Herbaceous plants are common ground cover species.

This region has the lowest diversity of plant species, compared to temperate and tropical regions. For instance, the state of Alaska has 133 native woody2 plant species with 33 reaching tree size, as compared to the state of Florida (tropical and semi-tropical) that has over 3100 native species, including over 300 native trees.3

Seasonal color of deciduous trees tends toward yellow or brown, while the low-growing plant cover can be brilliant with orange,