The effects of collection date and pre-storage treatment on the germination of blue oak acorns

Abstract

Concern about poor natural regeneration of blue oak in California has prompted efforts to artificially regenerate this species. Two studies examined the best time to collect acorns and the effect various pre-storage treatments, including soaking and drying, have on germination. Results indicated that acorns can be successfully collected over a fairly wide interval, extending from late August until late October. Acorns from all harvest dates had high germination, as long as they were not allowed to dry out before storage. However, the earlier the acorns were collected, the earlier they tended to germinate. Soaking acorns for a day prior to storage had little effect. Drying acorns, however, reduced both the rate and amount of germination. A 10% reduction in moisture content resulted in almost 40% less total germination, and all acorns that lost 25% or more of their mositure failed to germinate during the 10-week test interval. To ensure good seed quality, blue oak acorns should be collected directly from tree branches and placed immediately in cold storage.