Plant portrait - Oxalis deppei
This is a dainty little bulbous plant from Mexico. It grows about 20cm tall, producing a fountain of leaves from May until cut down by the first hard frosts of autumn. Red flowers are produced from about July and these will often also continue until the autumn frosts.
This is a delightful plant to grow along the edge of a bed. The clover-like leaves (every single one of them a lucky 4-leaved clover!) have a sharp lemon-like taste rather like sorrel. They make a very pleasant addition to a salad though should not be eaten in large quantities because all parts of the plant contain oxalic acid. This substance is found in a number of foods such as rhubarb and spinach. Whilst adding a pleasantly sharp flavour it can interfere with the absorption of certain nutrients in the body, especially calcium, and therefore needs to be treated with a certain amount of care.
The flowers have a similar, though to my mind even nicer, flavour to the leaves. If we can get Ajna (our 16 month old child) to stop eating them then they make a very pretty addition to the salad bowl.
The plant is not fully hardy in all parts of the country. We leave them out all winter in Cornwall without any problems, but I once lost most of them in a cold winter in Surrey. If in doubt it is best to harvest the bulbs in the autumn once the frosts have cut it back. Where one bulb had been planted you should find a number of bulbs clustered around a tap root that can be 5cm or more long and 3cm wide. This root is crisp and juicy, it occasionally has a slightly acid flavour reminiscent of the leaves but is more often almost tasteless. Rather like eating a supermarket 'Golden Delicious' apple really. Store the bulbs in a cool but frost-free place over the winter and then plant them out in April or May, covering then with about 1cm of soil.
The plants far prefer a sunny place and will need a well-drained soil if they are to thrive. They tolerate our wetter weather but prefer hot dry summers. They grew especially well last year with us in the summer drought. If you can leave them in place over the winter then they will increase steadily, though they are too well behaved to ever become a nuisance. If they ever do become too numerous then it is a simple matter to dig up the surplus in the autumn and pass them on to friends.
The database has more details on these plants: Oxalis deppei.