By Laura Lukes, UC Master Gardener of Butte County, September 7, 2018
The beauty of evolution is its reliance on trial and error, or adaptation. What works, works very well, and allows life in many forms to exist in some of Earth's harshest environments. The climatic conditions of the planet's seven Mediterranean Zones include between five and seven months of zero precipitation, and many days in a row with high temperatures of over 100 degrees Fahrenheit. These are challenging circumstances for any living thing. Yet a wide variety of plants have evolved clever strategies to survive these long, dry, hot periods.
Generally speaking, there are three major strategies employed by plants to survive annual drought conditions: desiccation tolerance; drought avoidance; and drought tolerance. These strategies evolved through millions of years of adaptation, and are endlessly fascinating in their ingenuity. (Please note that the survival tactics described below, the result of complex chemical and molecular biological processes, are simplified for this article.)
Desiccation Tolerance: To desiccate something is to thoroughly dry it. Tolerance of desiccation gives a plant the remarkable ability to survive almost total dehydration. This strategy is employed by mosses and ferns. Briefly, plants in this category have developed the ability to enter into, and recover from, anhydrobiosis, the cessation of metabolic activity as a result of low intracellular water content. Next time you are hiking in Upper Park or the foothills during the dry months, you can see this phenomenon for yourself. Find a patch of rust colored, crunchy dry moss on a rock, and gently pour a small amount of water on it. In seconds, what appeared to be completely dead vegetation will turn green and supple.
Another form of drought avoidance is early leaf drop. A good example of this is the buckeye (Aesculus), which occupies a unique ecological niche by being one of the first shrubs to leaf out and flower in early spring, and also one of the first to lose its leaves, well before the onslaught of summer heat and drought. Leaves demand precious nutrients and energy, and without them the buckeye can conserve these resources. During years of drought, and during sustained periods of high temperatures, our valley oaks and blue oaks lighten their metabolic load by dropping some leaves earlier than usual.
Drought Tolerance: Lastly, there is this catch-all phrase. Plants in this category are just better at functioning during annual drought conditions, due to a number of creative adaptations. Such plants are also called xerophytes; literally “dry plants.” They remain green all year round, but manage to save or store water, often through structural (usually leaf) morphology. Common structural adaptations for water conservation are:
- Thick, leathery leaves with waxy cuticles, which perform dual functions of cutting down on water loss and reflecting heat away from the plant. Our native Ceanothus (California Lilac) is a prime example of this.
- Small, thin leaves, which effectively reduce the surface area from which water loss can occur. The tiny yet highly fragrant leaves of Santolina typify this adaptation.
- Sunken stomata pits, which trap moist air and reduce water loss rates. Pine needles employ this strategy (as well as being small and thin).
- Hairy leaves, like those found on Cyprus ironwort (Sideritis cypria) or Lamb's Ears (Stachys byzantina), which shade the stomata and reduce contact from hot air, protecting plants from extremes of light and temperature.
Redundancy is a hallmark strategy for species survival (think two kidneys in human beings); and most plants employ more than one method of beating the hot dry summers of the Mediterranean climate. Now that you know what to look for, see how many of these ingenious biological adaptations you can spot.
By Eve Werner, Butte County Master Gardener, February 21, 2014
Lawns make an unbeatable playing surface. But many lawn areas, especially those in front yards, are rarely tread upon. Too often, they are grown by default for their reliable greenery. Keeping them lush and healthy expends resources in addition to water. Pesticides, fertilizers, and herbicides sometimes when applied to lawns can pose health risks to humans and leach into waterways. Gas-powered lawn mowers produce as much as 5% of the nation's air pollution each year. Native gardens, in contrast, provide beauty that is truly “green”.
The following three steps can guide you in successfully converting your lawn into a native garden.
First, observe. What existing trees and plants do you want to keep or remove? What are the sun and shade patterns? What types of grass grow in your lawn?
Next, kill your lawn. Homeowners can use either of two eco-friendly methods to kill their lawns. Solarizing involves heating the soil by covering it with a clear plastic tarp for four to six weeks during summer. It works best on fescue, ryegrass, and bluegrass, and with limited success on Bermuda grass. Sheet mulching is a method of layering materials (one of which is often cardboard) in order to inhibit the growth of weeds or (in this case) turf grass. Sheet mulching can be started any time of the year, takes six to eight months, works in sun or shade, and is effective on all grasses, including Bermuda grass. The UC Statewide Integrated Pest Management program website, http://www.ipm.ucdavis.edu, has information and instructions for both methods.
Finally, replant. Whichever method you choose, time implementation so that you are ready to replant in the fall. The cool temperatures and moist soils of October, November, and December allow native plants to develop the healthy roots they need to thrive with little water during the heat of summer.
Select a mix of trees, grasses, perennials, and shrubs for your native garden. Trees such as Western Redbud and Desert Willow add shade, privacy, and colorful blossoms. Dramatic bunch grasses like Deer Grass, California Fescue, and Blue Gramma grass enliven with texture and movement. The flowering evergreen shrubs Ceanothus ‘Concha,' Cleveland Sage, and California Buckwheat provide definition and screening. Perennials such as yarrow, BOP Penstemon, Naked Buckwheat, and California Fuchsia bring pizazz and pollinators into the garden. Sticky Monkey-flower and Hummingbird Sage brighten part-shade areas beneath existing trees. And, for those who miss the year-round green of their former lawn, there are evergreen groundcover manzanitas such as ‘Emerald Carpet' and ‘Green Supreme.'
It's a beneficial equation! A native garden can add a great deal to your garden while subtracting a chunk from your water bill.
On Monday, March 10, the Butte County Master Gardeners will present a workshop on this topic at the Chico Library, located at the corner of First and Sherman Avenues, from 10 to 11 am. The workshop, “Replacing Your Lawn,” will present techniques for lawn removal; it is one of a series of workshops the Master Gardeners will present on Mondays in March to help home gardeners deal with the present drought situation.