Most of the wood sorrels (Oxalis) are not very hardy. This is one of the few that can survive very cold winters unprotected (hardiness zone 5). It hugs the soil, reaching about 12 cm (4 in) high. Given the size of the plant, the purplish pink, funnel-shape flowers with dark veins are relatively large at 2.5cm (1 in). The crumply leaves are grey-green, divided in many segments arranged finger-fashion. The common name, silver shamrock, refers to the colour of the foliage. Both the flower and the leaves fold up at night or in overcast weather and are said to "go to sleep".
Although it comes from Chile and Argentina, in its native habitat it grows on mountain slopes where temperatures get quite cold. This explains why it can put up with cold winters (including 2013-14, one of the coldest on record when the thermometer went down to -35 C at Roche Fleurie). The important factor that allows this sorrel to survive till spring is to grow it in well-drained or sandy soil. We grow it in a raised bed where there is rich soil at the bottom but the top layers of the bed are sandy. We grow it in full sun. I notice that writers who live where the sun is not as strong (Britain) insist that it be grown in full sun. Those who live where the sun in stronger say it can tolerate some shade.
The bulbs are unusual looking in that they are very hairy and completely surrounded by a lot of fibrous material reminiscent of strands of coir. The bulbs should be planted just below the surface, and so some of the fibres stick out the ground (see the middle flower in the top row in the picture below). I would cut off all this fibre before planting the bulb if I were to do it again. The plant forms clumps and the leaves come out of the ground all bunched up and then proceed to spread out in bright sunshine. The flowers appear a few days after the leaves in late spring.
It is a very attractive, easy to grow bulb. The foliage is as interesting as the flower. It needs good, but well-drained soil. As long as it gets enough sun and does not sit in water in winter, come late spring, it blooms beautifully. Apparently it is easy to increase by dividing the bulbs in the off-season.
If it is kept in a cool greenhouse, it will bloom in winter. Here are a few of the plants that are in bloom at the same time as Oxalis adenophylla at Roche Fleurie :
|Potentilla neumanniana 'Verna'|
|Veronica umbrosa 'Georgia Blue'|