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.