Shamrock (Trifolium dubium), or Lesser Trefoil, is a member of the clover family. It – as the name suggests – has 3 leaves. It gets around 2-6 inches tall and often forms mats. The flowers are yellow and turn brown when seeds ripen. It flowers from May to October and the seeds ripen from July to October. It can fix atmospheric Nitrogen, so it can grow in nutritionally poor ground. It is suitable for a range of soil types, preferring moist – but well drained – conditions.