Reprinted with permission from the LA/Santa Monica Mountains Chapter newsletter
For any garden—in a canyon, on a slope, in an urban yard, perched on a rooftop or even planter boxes, tubs and pots enclosed by balcony railings—the amount of sun exposure versus dappled to total shade, the sources of water available, the type of soil, the type of drainage, the altitude and other environmental factors (i.e. wind, fog, salty or dusty air, seasonal temperature changes) will determine what species of plants will do well, whether they are native or non-native plants.
How does one analyze an urban habitat? Tall buildings become cliff faces with the same deep shade and harsh wind conditions as a long, steep-sided narrow canyon punctuated by narrow side canyons. Stucco walls or sidewalks may leach lime into adjacent flowerbeds, raising the pH. Wall colors and textures may absorb or reflect light, either mimicking a forest wall of trees or a bank in a desert wash. Street trees, street easement landscaping and irrigation become riparian habitat affecting the citizen's garden.
The soil may be topsoil original to the site, sterile subsoil, soil contaminated with construction debris, compacted, claypan, or all of the above including previous owners' gardening efforts. The size of the garden and its placement in relation to other structures (i.e. walls, foundations, sewer lines or septic tanks) may preclude planting large trees with correspondingly large, penetrating root systems.
All these factors are easily measured using a thermometer, sketches of shade patterns, maps of the garden in relation to other structures, maps locating existing irrigation or underground structures affecting the planting area, a moisture meter (or a calibrated finger), observations of local weather conditions (wind, dust, fog, etc.) and doing some judicious digging with a spade in the planting area. Having these data on potential garden sites enable the gardener to visit a native plant nursery, botanic garden or a native plant sale, ask informed questions, obtain accurate advice and buy plants with a good chance of success.
Urban citizens often view native flora as something unkempt and untamable, whether these citizens are environmental activists, or, more often, whether they are curious about native/non-native plants as viewed from car windows while stuck in the twice daily commuter traffic jam. These superficial impressions about native flora become a problem when the result is native plants placed helter-skelter in a front yard with no water and no care.
Cities usually have guidelines, sometimes regulations, on the types of landscaping allowed in front yards, especially in architecturally controlled neighborhoods. What can be defined environmentally as open savanna bounded by fencing or hedges under a certain height is the norm for most planning department regulations.
The persistent gardener might transform the front yard savanna into a native grass meadow with annuals in groups or interspersed with bunchgrasses in attractive patterns. Boulders, railroad ties, swales, wandering paths or other non-living elements can break up the banality of a flat grassy yard and emphasize the artistic side of landscaping. Many native shrubs such as lemonade berry (Rhus integrifolia), Rhamnus species, and Berberis species train nicely into hedges. Native annuals: Clarkia species, clovers (Castilleja species), poppies (Eschscholzia species), Lasthenia species, tidy tips (Layiaplatyglossa), Lupinus species, Nemophila species, Phacelia species, etc., make beautiful accents in beds or along sidewalks.
Maintenance and planning are the keys to success in these front yard landscapes. For example, every month of the year in southern California there are some native plant species either in bloom or loaded with colorful fruits or seeds. Planning for seasonal changes utilizing species having different flowering or fruiting times, using pleasing combinations of shape and texture of seeds, leaves and bark along with judicious cleaning and pruning provides a year?round joy to both homeowner and passersby. There is no reason why the native plant garden or landscape cannot be always graceful and glorious.
If the gardener wishes to produce a garden with the architecture of a particular plant community, the backyard may be preferable as a place to experiment until the gardener has a better understanding of which trees, shrubs and herbs will dominate, persist or be ephemeral in this backyard vegetative association. To attract and support local butterflies, birds and other local fauna, the plant community structure is the best type of garden.
Plant community architecture implies that species of herbs, small shrubs, tall shrubs and perhaps trees known to grow in vegetative associations in the wild will be planted in natural groupings in the garden. Typical plant communities in southern California are coastal sage scrub for hotter, drier locations; chaparral for slightly cooler, dry locations; riparian for wetter, shadier locations, grassland for flat, hot, thin soil locations. Native grassland and coastal sage scrub habitat requirements are essentially the same, except for topography. Coastal sage scrub is more often found on dry, hot, windy slopes in nutrient?poor soil, while grassland habitat generally is flat meadows, mesa tops or dry valley bottoms. Consider grassland to be coastal sage scrub without the shrub layer.
Coastal sage scrub architecture combines a shrub layer with shrubs generally under six feet in height, sometimes including cactus (chiefly Opuntia species), with a rich herb layer populated by herbaceous perennials, grasses, annuals and bulbs. Typical shrubs are bladderpod (1someris arborea), lemonade berry (Rhus integrifolia) and species of buckwheat (Eriogonum), sagebrush (Artemisia), sage (Salvia), and sunflowers (Encelia). Deerweed (Lotus scoparius) and perennial species of monkeyflowers (Mimulus) and Penstemon are found in both coastal sage scrub and chaparral habitats. Various species of needlegrass (Nassella) are common in the understory as are the annual flower species listed earlier.
Chaparral architecture may have a sparse tree layer of isolated trees of coast live oak (Quercus agrifolia) or small groves of California walnut (Juglans californica) and/or Mexican elderberry (Sambucus mexicana) where more water is available. Basically chaparral is dominated by tall shrubs and small trees, ten to twenty feet in height, though there is a rich understory of smaller shrubs and woody perennials. Toyon (Heteromeles arbutifolia) is a favorite choice of small tree with gardeners. Some common chaparral shrubs are chamise (Adenostomafasciculatum), hollyleaf cherry (Prunus ificifolia), mountain mahogany (Cercocarpus betuloides) and species of Ceanothus, Rhamnus, Rhus, manzanita (Arctostaphylos), scrub oak (Quercus). The herb layer may be sparse to abundant depending on the density of shrubs. Vines ranging from woody species of Clematis, honeysuckle (Lonicera) and wild grape (Vitis girdiana) to seasonal species of morning glory (Calystegia) and wild cucumber (Marah) compete in the wild for canopy space with the ever-present poison oak (Toxicodendron diversilobum). Poison oak is not recommended for any garden habitat.
Riparian architecture represents native flora living by seasonally flowing watercourses, year?round streams, seeps or springs. The tree layer is abundant. Often the trees are deciduous, i.e. sycamore (Platanus racemosa) and species of maple (Acer), cottonwood (Populus), alder (Alnus), ash (Fraxinus) and willow (Salix). The shrub layer ranges from tall shrubs like the fragrant mulefat (Baccharis salicifolia) to spreading, bushier species, i.e. blackberries (Rubus), currants/gooseberries (Ribes) and roses (Rosa). The herb layer contains annuals, ferns and grasses. Again various species of vines accent the tree and shrub canopies.
Whole gardens, with or without plant community architecture, can be designed with containers for balconies, paved patios or reinforced rooftops. Conditions are more restricting and the plant palettes available are more limited. Native plants having slow?growing or small root systems do well in containers with some extra care and water.
There is plenty of information about native plant gardening on the web, from native plant nurseries to the CNPS State website and local CNPS Chapter websites. Unfortunately these wonderful sources do not agree about the characteristics of all California flora available for gardens. Some judgment and experimentation is required for native plant gardening. All gardening is an adventure full of surprises.
—Betsey Landis, author of Southern California Native Plants for School Gardens