Oxalis species: Sorrel

Family

Oxalidaceae

Common Names

Shamrock, wood sorrel, soursob, Bermuda buttercup, oxalis Irish shamrock - O. acetosella.

Plant Description

Comprising over 800 species, Oxalis are found widely in many parts of the world. Most are wild flowers or weeds, but some are cultivated as garden and potted indoor plants for their attractive foliage and flowers. Annual or perennial herbs growing from scaly bulbs, rhizomes, or taproots. Stems are thin, decumbent or erect, up to 40cm in height, and haired or hairless. Leaves are palmate, cordate, with 3 leaflets that tend to fold at night. The sap and plant parts are sour to the taste. Infloresences are single flowers or cymes or umbels. Flowers are bell-shaped, 5 petalled, and in various colors ranging from white to yellow and pink to purple (Fig. 293, Fig. 294 and Fig. 295). The flowers fold up at night. Fruits are capsules that are explosively dehiscent , scattering numerous seeds.

Figure 293. Oxalis hybrid.

Figure 294. Oxalis hybrid.

Figure 295. Oxalis purpurea.

Toxic Principle and Mechanism of Action

Soluble oxalates are present in all parts of the plant and are responsible for the sour taste of the plants. The sap is acidic due to the presence of potassium oxalate and free oxalic acid, with total oxalate in some species being 16% dry matter [1]. If eaten in quantity the oxalates can induce hypocalcemia and oxalate nephrosis. Most poisoning has occurred in sheep that graze stands of Oxalis pes-caprae in Australia [2]. Goats have also been affected [3].

Risk Assessment

It is unlikely that household pets or children would eat much of the plant because of its sour taste.

Clinical Signs

Sheep that have eaten large amounts of the plant become depressed, ataxic and recumbent because of hypocalcemia following the formation of insoluble calcium oxalate. Oxalate crystals may be seen in the urine and animals die from an oxalate nephrosis.

In the event oxalate poisoning is confirmed, the intravenous administration of calcium borogluconate may rapidly reverse hypocalcemic effects, but oxalate nephrosis may not be affected and animals may die several days later from renal failure.