Buttercup Oxalis-Woodsorrel Family

Oxalis pes-caprae

Bermuda buttercup, sour grass

Characterisitics. This weed is sometimes grown as an ornamental but has escaped and become a frequent pest of turf, gardens and other ornamental situations. It is quite similar to woodsorrel but often grows more upright, has much more showy flowers and reproduces primarily by small bulbs. The leaves and stem contain oxalic acid which gives then a sharp sour taste. This plant is sometimes eaten by humans which is perfectly acceptable in small quantities. However consumption of large quantities of this plant (oxalic acid) can bind the body’s calcium supply and result in nutritional deficiencies.

Identifying Characteristics. This weed typically grows in upright clumps. Seedlings are not generally encountered in California. It has fully subdivided leaves, each consisting of three heart-shaped leaflets resembling clover leaves. Flowers are attractive, but are a nuisance when they spread into gardens or shrubs like this juniper (pictured here). Flowers occur singly or in clusters on the ends of slender leaf stalks; each flower has 5 yellow petals. This species closely resembles woodsorrel but often grows more upright, has more showy flowers, and reproduces largely by bulbs. Bermuda buttercup (buttercup oxalis), a low growing perennial broadleaf plant with shamrock-like leaves, is found throughout California up to 8200 feet (2500 m). It inhabits agricultural land and other disturbed areas and is a common weed in artichoke fields on the Central Coast and in irrigated landscapes. It is related to, and closely resembles, creeping woodsorrel, Oxalis corniculata. Both species contain variable levels of oxalate compounds that can cause death in livestock when consumed in large quantity. They are attractive but are a nuisance when they spread into gardens or when they infest shrubs. Sometimes Bermuda buttercup is grown as an ornamental.

The compound leaves are a typical three-leaf clover shape, each consisting

of three heart shaped leaflets.

The showy yellow flowers occur singly or in clusters each at the end of a slender elongated stem and have 5 yellow petals. Unopened flowers have a characteristic

elongated cone-shape.

Characteristics Important to Control. This is a weed that is very difficult to remove. You must dig out all the little bulblets, or it will keep coming back. Some people use them in mass plantings in front of their houses, where they do have large yellow flowers on tall stakes.

It grows from clusters of little bulblets and spreads itself by making new bulbs & by reseeding. Getting all the bulbs out is impossible-too small, too profuse- but you are reducing the population by digging out some of them. Like all bulbs (think of daffodils), the bulbs are fed by the foliage, so even just chopping the tops off as soon as they appear helps to exhaust the roots. Not all the bulbs will sprout at the same time, so this must be a continuous project all season. Don't let it go to flower, attack it ASAP!

Alternatively, you can use Roundup on the foliage, which is carried to the bulblets and kills them. Any herbicide rightly makes some people nervous, but Roundup is generally considered safe by knowledgeable professionals (it has a very low toxicity to people and animals in the first place, breaks down on contact with the soil into non-toxic compounds, & has been around a long time). On general principal, I only use it on a couple of types of weeds, Bermuda buttercup among them (also Bermudagrass). You need to continue to spray it on the foliage as new plants appear.