Bitterbrush Fruits

Continuing the topic of bitterbrush (Purshia tridentata – see “Bitterbrush in Winter” 01-12-2018)), I have photographs of bitterbrush fruits taken in May and July on Timbered Crater (Shasta County CA) and along Modoc National Forest Road 40N11 near Adin CA (Modoc County).

The pale yellow (sometimes white) flowers of bitterbrush occur singly, either terminally on the branch or in the leaf axils. The 5 sepals are joined at the base to form a receptocalyx. Receptocalyx is a combination of receptacle, the top of a stem that is enlarged and bears the flower parts, and calyx, the sepals collectively. The 18 to 30 stamens are inserted in a single row on the flower margin along with the five petals. The stamens and petals surround a pistil with a single-celled superior ovary.

The fruit that develops from the bitterbrush flower is a leathery, oblong achene (one-seeded fruit that does not open). The receptocalyx persists and surrounds the base of the achene. As the fruit develops it tapers on the end opposite the receptocalyx. The style (center portion of the pistil between the ovary and stigma) also persists in the fruit and resembles a string attached to the tapered tip. A fully mature bitterbrush fruit to me resembles a dunce cap tucked among the sepals.

Bitterbrush is bitter tasting, however, it is one of the most important browse shrubs in the Western United States.

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