Succession

In Designing California Native Gardens, Alrie Middlebrook describes her use of succession (moving through a series of simple-to-complex planting stages, culminating in a final stage) in her garden designs. For slower growing shrubs and trees, she recommends planting them with ample spacing, so they can grow to their mature size without overcrowding, and filling in with shorter-lived grasses, bushes and flowers. She gives the example of establishing an oak woodland garden in a hot area of a yard. While the oaks were getting started, she planted chaparral species that could tolerate the heat, and then started to introduce oak woodland understory plants as the oaks became established and their watering needs changed.

I saw succession at work while growing up in Southeast Alaska. A marker at the Mendenhall Glacier Visitor Center indicates the location from which the glacier had receded only a hundred years before. The glacier left behind barren, ground bedrock; over time moisture- and air-borne soil particles began to accumulate. Early plant species—such as fireweed, grasses, and alders—moved in. Alders can live in poor soil, and fix nitrogen, so they contribute to building the soil. Over time, spruce trees replaced alders – shading them out. A new understory of shade-tolerant plants emerged, such as fern, horse tails, moss, devil’s club, and Indian rhubarb. During this process, organic material accumulates and decomposes, further enriching and developing the soil.

Succession at work - this peninsula at Mendenhall Glacier used
to be barren rock just several decades ago.

The key ideas for using succession in the home garden are: (1) enrich the soil naturally, and (2) design an attractive short-term garden that allows slow growing trees and shrubs the space and time they need to get established.

Oak Woodland Plant Community

The oak woodland plant community varies by region – Northern and Southern California, and coastal and foothill. Here in the San Francisco Bay Area, the oak woodland plant community is dominated by the Coast Live Oak, and is under the influence of fog and ocean breezes. Because of our microclimates, plant communities often intermingle if conditions are right, but a typical base palate of plants include:

• Trees: coast live oak (Quercus agrifolia), California bay (Umbellularia californica), California buckeye (Aesculus californica), tanbark oak (Lithocarpus densiflorus), and madrone (Arbutus menziesii).
• Shrubs and understory: toyon (Heteromeles arbutifolia), manzanita (Arctostaphylos manzanita), coyote brush (Baccharis pilularis), Western redbud (Cercis occidentalis), California sagebrush (Artemisia californica), California fescue (Festuca californica), common wood fern (Dryopteris arguta), and sticky monkey flower (Mimulus aurantiacus).

Toyon berries in winter, add color to the garden and attract birds

Using these plants together—with their similar watering, drainage, and soil needs—can help ensure a successful native oak woodland garden that attracts pollinators and wildlife.

For photos of Northern oak woodland plants: http://www.laspilitas.com/nature-of-california/communities/northern-oak-woodland/plants. For information about oak woodland plant communities: Plant Life in the World’s Mediterranean Climates (Peter Dallman), and Designing California Native Gardens (Glenn Keator and Alrie Middlebrook).

Designing Gardens with California Natives

This is a great reference for designing beautiful, ecological gardens, using a plant community approach. The book focuses on California native plant communities (plants that grow together because of similar adaptations), including bluffs and cliffs, redwood forest, desert gardens, montane meadows, mixed evergreen forest, oak woodlands, grasslands, chaparral, riparian woodlands, and wetlands. The authors are Glenn Keator and Alrie Middlebrook; the publisher is University of California Press.

For each garden design, the authors provide a unique representation of the garden plan, practical project information, descriptions of plants and the plant community, and information about places to visit to see the plant community in nature. The resource section provides a comprehensive list of native plant sources, books, botanical gardens and arboreta, public gardens, websites, and a seasonal calendar for managing native gardens.

Glenn Keator is a botanist, author, and lecturer with extensive knowledge of California native plants. I’ve had the pleasure of taking his Mediterranean plant ID class at Merritt College. Alrie Middlebrook founded Middlebrook Gardens in San Jose, which specializes in designing California native gardens, and is also an author and lecturer. I was intrigued by her use of succession (moving through a series of simple-to-complex planting stages, culminating in a final stage) in her garden designs.