"Flowering and Fruiting- Northern red oak is monoecious. The staminate flowers are borne in catkins that develop from leaf axils of the previous year and emerge before or at the same time as the current leaves in April or May. The pistillate flowers are solitary or occur in two- to many-flowered spikes that develop in the axils of the current year's leaves. The fruit is an acorn or nut that occurs singly or in clusters of from two to five, is partially enclosed by a scaly cup, and matures in 2 years. Northern red oak acorns are brown when mature and ripen from late August to late October, depending on geographic location (30)."
Anthony R. Brach, Ph.D.
Harvard University Herbaria c/o Missouri Botanical Garden
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