The thick, vertically-oriented leaves of manzanita protect them from sunburn and moisture loss
Plants that evolved in hot, dry climates have a certain look that not everyone finds appealing. Perhaps the cultural influence of east coast gardening is still strong or the lush growth of wet-climate plants represents life and fertility, but we still perceive this look as “normal”.
The aesthetic of high-water use plants is an adaptation to their native conditions, just as the unique aesthetic of summer-dry plants represents their adaptation to drought, heat, and in some places, intermittent wildfire:
A thick, waxy cuticle layer partially obscures chlorophyll, giving foliage a bluish-gray hue rather than the “pure” greens of summer-wet species. Called sclerophyllous, this adaptation reduces water loss and insulates against the heat. This foliage is tough, leathery, and thick; a high essential oil and fiber content provides pest protection. Taking a lot of energy to produce, sclerophyllous leaves are evergreen and last about two years.
Small leaf size reduces surface area for evaporation to occur.
Fuzzy foliage is a result of non-living plant hairs (trichomes) on the leaf surface, reducing water loss and sunburn. The foliage often appears silvery white.
Vertically-oriented leaves, such as those of the manzanita, also prevent sunburn. Some species curl their leaves to prevent full sun exposure.
Dropping leaves in summer is a strategy plants with more tender foliage use to prevent water loss. Also called seasonal dimorphism, plants shed larger leaves, starting with those near the ground, before growing smaller leaves. Larger leaves appear again after the rains begin. Unless leaves are diseased, leave them on the ground as a mulch. California's tradition of hygenic, irrigated landscapes can make the late-summer aesthetic difficult to accept!
Low, bushy growth shades the ground, keeping roots cool and preventing moisture loss from the soil. It also protects the plant from dessicating winds.
Wildfire survival is essential for plants native to chaparral ecologies. Plants survive as seeders or sprouters, the latter being most relevant to home gardeners. Sprouters regrow from specialized roots (burls) that store extra starches, allowing them to survive and send up new shoots after wildfires. This can frustrate gardeners who are trying to grow sprouters like Ceanothus or Western Redbud as single-trunk trees. Sprouts will emerge from the base throughout the plant's life, so keep this in mind when deciding how to cultivate them. On ther other hand, sprouting is advantageous for rejuvinating scraggly plants: just coppice them at the base! For more on pruning California natives, see the Yerba Buena Nursery Guide to Pruning.
Tolerance of alkaline soils is important for plants native to summer-dry climates, where high pH limits nutrient availability. Local soils are neutral to alkaline, making this an important factor in selecting plants for your garden.
Irrigation allows us to defy California's summer-dry climate and use “normal” plants from east coast climates, but the drought necessitates a stronger sense of place, to express the local climate and soil in our plant choices.
For more about water-wise gardening, visit the San Joaquin County Master Gardener page on Low Water Use Landscapes. If you have a gardening related question you can contact the UC Master Gardeners at 209-953-6112. More information can be found on our website.