Guide to Growing California Oaks

Choosing a planting site

Choosing a planting site for an oak woodland restoration project

Every oak planting is in a sense an experiment.  Variation in weather patterns, acorn crop, and animal herbivory means that no two plantings will be exactly alike.  Careful monitoring, adjustment, and replanting may be needed before the objectives of an oak planting project are realized.

Oak woodland restoration is necessary where natural regeneration has failed in the past or is currently failing. Suitable sites for restoration are those in which site management has inhibited oak woodland regeneration but soil and climate factors are not critically limiting for seedling establishment.

Evaluate current condition of planting site

1. What is the current composition of the vegetation? Current vegetation is the starting material of a restoration project and may include desirable species to be favored as well as undesirable species to be suppressed or eradicated. The passive movement of native plants, lichens, fungi, actinomycetes, and bacteria into the planting is favored if oak woodlands adjoin the restoration site.

2. Is it likely the site supported oaks in the past, and if so, what species? Existing woodlands and oaks in and near restoration sites are the best clues to use to answer these questions. Historical photos and accounts can also be helpful, but it is usually impossible to definitively reconstruct presettlement oak woodland vegetation of a currently unwooded site. Nonindigenous plants introduced by the earliest European explorers and early Spanish colonists had become widespread before the 1850s, and much of the original oak woodland canopy was cut or burned off by the 1890s. For most areas, the earliest aerial photography dates to the 1930s and very little ground-level photography was taken before the 1880s. Thus, the photographic record begins after major changes were completed.

3. How have management practices and other human activities shaped current site conditions? Although information gaps will typically exist, historical site analysis can reveal important details about the succession of human impacts that have shaped the current landscape. Because site specific historical data is difficult to obtain, it is often necessary to rely on more regional historical information. However, the history of land ownership and management for many parcels is so complex that one should generally not assume that past management has been uniform across wide areas.

4. What is the overall site quality? Site quality is the ability of a site to support oak establishment and growth. Site quality is primarily related to physical factors such as soils, climate, hydrology, and topographic position. However, oak survival and growth are also constrained by competing vegetation, herbivores, and disturbance factors that affect overall site quality for restoration purposes. The analysis of past and current vegetation and management can help one determine what outcomes are possible for a site, and what inputs may be necessary to achieve these outcomes. A key question to be addressed in this analysis is whether a site can still support the type of woodlands that were historically present. For example, valley oak is found where its roots access relatively shallow water tables or exploit a large reservoir of available capillary water stored in the soil profile. In historic valley oak sites where precipitation and soil available water holding capacity are low, significant lowering or elimination of shallow water tables may render the site unsuitable for this species.