Flowering and Fruiting
Staminate catkins are elongate and erect, 5 to 10 cm (2 to 4 in) long. Blossoms may appear in the spring, summer, or autumn. However, most tanoaks bloom in June, July, or August. Trees at lower elevations and near the coast bloom earlier than trees at higher elevations and farther inland. The plant is monoecious.
Almost all the flowers, both male and female, are borne on new shoots (22), where they grow from the axils of the new leaves. Flowers also occasionally develop from buds found at the base of leaves of the previous year's growth.
Female flowers are borne at the base of erect male catkins. The profusion of yellowish blossoms that sometimes conceal the foliage suggested the tree's specific scientific name. The calyx is pale green; the stamen filament is white; and the anther yellow.
The seeds, which are similar to oak acorns, ripen in the second autumn. Seeds are usually borne singly, in twos, or in threes (25), but sometimes more are clustered together.