If you’ve visited or lived in the East, Midwest, Pacific Northwest, or any other temperate climate region of the world, you may have noticed how green those regions look. Big trees and shrubs, covered in large, green leaves, thrive on warm summer rains. When winter’s cold arrives, the trees and shrubs drop their leaves and go into dormancy — a kind of suspended animation — while the plants wait for spring’s warmth to return.
Our region is not green. It is bright and sunny, with scrub-covered hills that are olive green from fall through spring, then brown through summer. They respond to our unique Mediterranean climate pattern. Rain falls during mild cool temperatures of autumn, winter, and early spring. There’s no rain during summer’s dry heat, which is nice for people, but challenging for plants.
Big green trees and shrubs are rare in deserts, too. Some rain falls in winter, but the biggest rainfall occurs during muggy summer monsoons. Deserts get extremely hot, with little rainfall overall, and — other than during monsoon season — the dry air literally pulls moisture from plant leaves.
Plants native to these dry regions have evolved similar survival strategies for extreme heat and limited water. Many native plants go dormant in the heat. Their leaves drop, and branches stay bare until the cool temperatures of fall when new leaves sprout, and plants resume their growth.
Small leaves and narrow leaves are drought strategies, too. Plants lose moisture by evaporation from the surface of their leaves. Larger leaves, with more surface area, lose the most water. Smaller and narrower leaves have less surface area, so they lose less water to the atmosphere.
While we love the feeling of fuzzy leaves, that isn’t why they are covered with fuzz. For plants, that layer of fine hairs is a vapor barrier that slows down water evaporation from leaf surfaces. The hairs shade the leaf from blistering sunlight, too, and their silver color helps deflects sunlight. All are strategies for surviving heat and drought.
Leaves that don’t contain much water, don’t have much water to lose. Some dry-climate plants evolve leaves that are leathery or high in oils, rather than fleshy and water-filled.
Succulence is an obvious drought strategy. In the rainy season, succulent plants absorb water and store it in their stems, roots, and leaves. In the dry season, they use up that moisture to survive.
Next time you see a barrel cactus, notice how beneath the spines, the plant itself is baffled like an accordion. The baffles expand as the plants fill up with water during the rainy season. As the water gets used, the baffles shrink back down.
Even spines have a drought purpose. True, they protect plants from predators, but for some cacti, spines harvest dew from the cooler evening and early morning air, then direct it right into the plant or to the roots.
All plant leaves are covered in a thin layer of wax to keep them hydrated for a longer period. For some hot climate plants, the protective wax layer is so thick that it comes off when you rub the leaf.
These adaptations make for gardens that look entirely different from big, broad-leaved temperate gardens, yet are no less attractive. So, next time you are looking for plants that will thrive in your garden with little or no irrigation, look for these features:
- Silver leaves
- Fuzzy leaves
- Waxy leaves
- Leathery leaves
- Oily leaves
- Small leaves
- Narrow leaves
These characteristics are rules of thumb since, for example, silver leaved plants are native to many different climates. So, do your homework. Research plants to find those best suited to our waterwise gardens. Then, then come up with a plan before you go shopping. That’s the best part, of course!