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Bermuda Wood Sorrel

© Gregg Pasterick

Last winter in southern California I marveled at all the big, bushy yellow wildflowers in bloom, all of which were Encelia or Coreopsis species. They were big, showy things, in your face and impossible to ignore. But there was another rather ubiquitous yellow wildflower in bloom, nearly a ground cover but often so widespread it was every bit as impossible to ignore as Giant Coreopsis or Bush Sunflowers. That was Bermuda Wood Sorrel, or Bermuda Buttercup (Oxalis pes-caprae.)

A non-native species, Bermuda Wood Sorrel comes to us from South Africa. In southern California it turns up in coastal gardens and fields and inland landscaped areas. It is often cultivated as an ornamental - and what a lovely ornamental it is - and though it is sometimes found in lawns, it's only a problem in gardens or shrub areas; i.e. places it's not wanted.

It is a perennial that grows from bulbs in the fall and flowers in late winter or early spring. The plant forms a single, short, vertical stem that is mostly underground. The leaves, which are large and somewhat fleshy, form a rosette above the surface of the ground. Small, whitish bulblets pop out on the stem at the base of this rosette, and new bulbs form underground. It reproduces mostly by way of these bulbs.

The flowers are bright yellow and grow up to 1 and 1/2 inches in diameter; the seedpods resemble the bulbs.

Bermuda Wood Sorrel and its many cousins have their own family, the Wood Sorrel Family Oxalidaceae) (of course!) The family and generic monikers are from the Greek oxys, which means "sour," and refers to the tart taste of the leaves, a consequence of their oxalic acid content. The leaves of some species can be used in salads, but sparingly due to that oxalic acid. (In large quantities, oxalic acid can hinder the body's supply of calcium, which can lead to a nutritional deficiency. The amount of oxalic acid in the leaves will be reduced if the leaves are cooked.)

Members of the family can most easily be identified by their palmately compound leaves. These leaves, with their three leaflets, resemble three-leaved clovers, but do not sport a chevron, as do clover leaves. Sometimes these palmately compound leaves have more than three leaflets; that four leaf clover you once looked over? It was probably a wood sorrel.

Bermuda Wood Sorrel, grown as an ornamental, can spread like a mint throughout the garden, competing with other plants. Yanking it up by hand will weed it out to some degree, but because it grows by bulbs it is difficult to be rid of once and for all. It can also spread into the lawn, but mowing reduces its invasiveness. And keep in mind, when you're hauling soil from one part of the yard or garden to another, do not take soil where Bermuda Wood Sorrel has grown. Its bulbs are probably in there, ticking time bombs of invasive botany, just waiting to turn your flowerbed in an episode of "24."