Why We Should Consider the Chaparral, Choosing Plants for Water Efficiency and Healthy Ecosystems
an article in the Caltivate series
By Stephen Blewett, ASLA, PLA
The days of planting tropicals are over and I couldn’t be happier! As landscape architects and designers in California we’re often faced with many public policy related constraints. One such constraint is the model water efficient landscape ordinance or MWELO. MWELO’s purpose is to “promote the conservation and efficient water use and to prevent the waste of this valuable resource.” It does this by setting a “maximum applied water allowance as an upper limit for water use and reduce water to the lowest practical amount.” See you later tropicals! We’re not going to bore you with specifics, but these calculations, gathered by scientists, are driven by geographic location.
For example, one of the factors in determining water allowances is evapotranspiration, water lost to the atmosphere. With all the topographic variation in California, mountains, valleys, beaches, canyons, etc., this rate cannot be constant. Water loss due to evapotranspiration on north-facing slopes of the San Gabriel Mountains is considerably lower than rates on south-facing slopes. The reason, here in Los Angeles south-facing slopes are exposed to the sun during the hottest part of the day, while north-facing slopes benefit from less exposure. So, we can conclude that anything planted on the south-facing slopes will lose more water through evapotranspiration than that same plant on a north-facing slope. So, how does this relate to the chaparral? Well, before that, let’s define chaparral.
The chaparral, often referred to as the Mediterranean climate, is a term applied to an ecology largely confined to near 30 degrees north and south latitude, along the western margins of the planet’s continents. Here in the US, and particularly in California, you find it on south and west facing slopes in the Peninsular Range in San Diego, the south and west facing slopes of the Transverse and Coastal Range in Los Angeles, and along the western slopes of the Sierra Nevada (see graphic, above). Due to its orientation (south and west facing – remember this is exposed to the hottest temperatures during the day) the chaparral is exposed to excessive amounts of evapotranspiration. In response to high rates of evapotranspiration, and limited water supply, vegetation of the chaparral have evolved small, waxy, leathery leaves (see sclerophyllus), which helps retain moisture, and deep tap roots to access deep pools of water.
So, now you have a basic understanding of the chaparral. To recap, we know that the chaparral occupies southern and western slopes, and because of the orientation, in L.A., is exposed to continuous hot afternoon sunshine, sapping available water from the atmosphere via evapotranspiration; in response, plants have adapted small and waxy leaves and deep tap roots to combat excessive moisture loss – smart!
We also have a basic understanding of MWELO – save water, via efficient landscape practices. As landscape architects, we can practice greater efficiency through smart irrigation systems like drip and weather-based controllers, and using low-water use plants in our designs. Which leads me to the case for the chaparral.
The chaparral is the most drought-resistant plant material in the L.A. Basin. With all the restrictions on water-use why not employ the plant material of the chaparral? Well, I’ll save it for another time, but fire is a critical component of the regeneration of chaparral vegetation. Chaparral needs fire to regenerate and along with their waxy leaves and deep tap roots, contain foliage inherent oils, allowing them to burn readily, thus stimulating new growth and regeneration. As a result, many cities that lie adjacent to chaparral ecosystems, restrict the use of many of these plants. However, there are still plants among this community available for use in our landscapes, and several nurseries carry safe chaparral stock – see our list below.
So, it’s time. Plant more chaparral. Doing so means more water savings, richer populations of local pollinators and wildlife, healthy ecosystems, and healthier communities for generations to come. Do your part, plant local, plant chaparral. See some of our favorites below.
To learn more about the chaparral, check in with us for our next article in the series where we discuss fire’s relationship to the community, invasive plants, and subsets of the chaparral. Looking further ahead we’ll tap into other local plant communities, like the Coastal Sage Scrub, Alluvial Scrub, Oak Woodlands, Riparian, etc. and how they too contribute to a healthy community.
We’re not the go-to for information so read more about it yourself in the following publications:
· A Natural History of California by Allan A. Schoenherr
· Introduction to the Plant Life of Southern California by Philip W. Rundel and Robert Gustafson
Native Nurseries carrying plants of the Los Angeles Basin
As always, we’re here to help and excited to offer our expertise, so please reach out to us.