What is most memorable about me?
The cactus in the thumbnail picture at right is speaking very explicitly about the environment it is equipped to live in. The spines to keep would-be herbivores away and the swollen, succulent stem with a waxy coating to store and keep water for those really dry periods represent two clear statements about the native conditions that this plant endures.
While our spiny friend is quite explicit, other plants are much more subtle about themselves. However, to greater or lesser degrees, similar structures or characteristics can be understood as clues to your plant's needs. This valuable information can be found in the leaves, stems, roots and flowers.
Below I'll touch upon some of the major habitat types and the characteristics found on plants growing in them.
Hot and Dry
Plants that thrive in these conditions may have smaller leaves, and the leaves will often have coatings or coverings of some type. Waxy layers, profuse hairiness or pubescence, and light or reflective leaf surfaces are all methods for keeping the heat down and retarding water loss. Leaves are thickened when compared to those on plants in more hospitable environments. Such plants must have protection from herbivores as well, so spines, toxic juices, or general unpalatability are also commonly displayed.
Fitness doesn't stop with leaves; the stems are frequently thick, caudiciform (fat) or, as in the case of cactus, very thick, and equipped for water storage. This swollen characteristic can extend to the root zone as well, providing long-term water and nutrient storage safe from direct exposure to heat and dryness.
Hot and Wet
This is the quintessential rain forest situation, but morphological types vary greatly depending upon the soil or substrate. Plants growing in very open or exposed conditions, such as epiphytically in trees, on cliffs, slopes or rocky areas will exhibit some characteristics that are reminiscent of those on plants in drier climes. Some of these plants will have thckened or waxy leaves (as in bromeliads, see Tillandsia picture at left), swollen stems or pseudobulbs (for example, orchids), and roots that are intolerant of constantly moist heavier soil mixes. Those individuals that do thrive in the wet soil will have larger and thinner leaf blades, often with "drip tips" and channeled veination to speed water off the leaves, and leaves held in such a manner as to shed water most efficiently. An example of this type of plant is Spathiphyllum, a plant that in native habitat often is found growing in swampy areas. For such a plant, drying out is an extreme stress situation.
Cold and Dry
Plants here have some of the same characteristics as those in the hot and dry zones, with the addition of resistance to chilling injury and freeze damage. They may shed all leaves entirely and take on a darker coloration in the cold season in order to absorb more heat from the sun. Others have leaves hardened against the cold, with cell fluids able to resist ice formation even below freezing. Their seeds will require a period of stratification, or moist chilling conditions, before they will germinate. In high latitudes or above the treeline on mountains, plant height and size decrease drastically, providing protection from the harsh conditions. The extreme example of this situation is the tundra environment. Microclimates become extremely important with plants in these zones.
Cool and Wet
This is what could be described as the temperate rain forest. Plants here have a mix of characteristics, blending some similar to those in the tropical rain forest with those in colder temperate climates. Some plants that thrive abundantly here will languish in hotter wet climates. Many delicate mosses and ferns grow well in this environment, needing the high humidity without the high heat of the tropics. The tallest trees in the world come from environments like this, such as the Redwood (Sequoia sempervirens), the Mountain Ash (Eucalyptus regnans) and the Douglas Fir (Pseudotsuga menziesii).
Nature being what it is, variety reigns, and this is no less true when discussing the plethora of environments in which plants and trees grow here on our planet. Some areas are hot and dry at one time of year, then cool and wet at another. Many plants can thrive in a range of habitats, tolerating conditions that are not ideal, but not inhospitable either. Be ready to learn from the experiences of other gardeners as well as from your own experiences. Your conditions may be on the fringes of what a plant can thrive in, or your situation may be too extreme for your chosen specimen. Above all, observe and learn, and let your plants speak to you in their own language, the language of what they are.
Photo credit: Public Domain Clip Art