10. Native Plant Communities
Its time to get into a third level of discussion about native plants appropriate for the home garden. I have already written about the very macro level of Plants of the Mediterranean Climate Zone, and the traditional definition of California native plants within the California Floristic Province. Now I would like to go to a more micro level and look at California’s Plant Communities.
What Is a Plant Community?
What’s this - plants live in communities? Indeed it is true, but not exactly like our human communities. Certain plants associate together because they like the same soil, climate and other environmental conditions, and each fills a certain niche within these conditions to form a complementary grouping. For example, we have the well-known Redwood Forest plant community, with its signature tree, the Coast Redwood (Sequoia sempervirens). These trees live in valleys along the coastal fog belt, but not so close to the ocean to have significant salt air. They obviously create a shady understory climate, and all the needles they drop to the ground form a very soft, nutrient rich surface. The trees also condense and drip some of the fog-borne moisture into the soil, all leading to a great environment for ferns, mosses, and fungi. Not all plant communities are this distinct, and in fact there is some disagreement about the usage of this categorization in the world of the plant sciences. But for the purposes of learning what native plants will work well together, the plant community is a useful concept.
Plant Communities Common to the Bay Area
There are about 28 different plant communities in California that include everything from the Coastal Marsh to the Alpine Fell Field and various kinds of Forests, Woodlands, Grasslands and shrubby ‘Scrub’ communities. For the less scientific purposes of finding plants to use in your yard, I prefer to simplify it down to the following ones common in Coastal Northern California:
Chaparral
Coastal Sage Scrub
Coastal Prairie
Valley Grasslands
Oak Woodland
Mixed Evergreen Forest
Redwood Forest
From this list you can determine the ones that were most likely to exist naturally in your area and narrow down the native plants that are likely to work well there. You are also able to get closer to plants that would be truly native to your site, which makes more sense to me than being able to select anything from the entire California Floristic Province and call it a “native” plant garden.
A great example of the usefulness of this approach is gardening with a Coast Live Oak (Quercus agrifolia). This is a beautiful tree that is a major feature of the Oak Woodland plant community, and is common to Bay Area climates and clay soils. It is highly valued in gardens, but very sensitive to excess water that typical garden plantings need. By looking at the other plants native to this community, you find those that naturally like these dry shade conditions, such as the bunch grass California Fescue (Festuca californica) and the deciduous Snowberry shrub (Symphoricarpos albus).
Other Plant Communities
In addition to the common plant communities, it is also useful to be aware of the less common ones of the desert, wetlands, streams and rocky bluffs because their environments may resemble certain tough and/or unusual situations. For example, the succulent Stonecrop (Sedum spathulifolium) and the flowering Seathrift (Armeria maritima) are native to the rocky bluffs of the coast and so become natural choices for use on green roofs with thin soil profiles that are near the coast.
Benefits of the Plant Community Approach
A few benefits of approaching your planting design in terms of native plant communities have already been mentioned – you are able to get closer to truly site-specific native plants, and you are getting plants well adapted to your local conditions. Another great benefit is the excellent habitat you are providing for locally native birds, insects and animals, which naturally prefer the native plants they evolved with. The connections you can make to the local natural environment are also exceptional when you are using the same plants that are found in your nearby open spaces and parks – you achieve a sense of place that connects you to the greater outdoors.
Limits to this Approach
Taking it one step further would be to attempt a true restoration of a native plant community by installing all the major plants of the exact community that existed on your property before human occupation. This can be a good idea if approached judiciously, especially if you have a large area and live on the edge of an open space. However, there are several reasons not to take the plant community approach too far. First, the typical yard is not likely to represent the native environment exactly. Developed areas that have been occupied for more than a few years will have modified soil, climate, air quality and ecology. You also inherit plethora of weed seed that will be major competition for many types of native plants.
Another reason is that, at least up close to your house, you probably want your garden to look beautiful and hospitable year round. Not all plants native to a community are going to look great in a garden, and many look good for only a short time. Because of our summer dry climate, many native plants go dormant from mid-summer until the winter rains begin, which could leave you with a brown garden of dried leaves and bare spots that might even be a fire hazard.
So it is important to be selective about which plants that you use from a certain native plant community. It is ultimately a subjective, aesthetic decision, but I think it is best not to take the plant community approach too literally. Consult your favorite Landscape Architect for knowledgeable design thinking on plants within a native community that will look great in your yard and take another step towards a more environmentally responsible garden.
References:
Designing California Native Gardens, by Glenn Keator and Alrie Middlebrook
California Native Plants for the Garden, by Bornstein, Fross and O’Brien
Cal Flora web site www.calflora.org
A Manual of California Vegetation, Online Introduction, California Native Plant Society, http://vegetation.cnps.org/