The colourful clovers and trefoils, members of the genus Trifolium, are important as forage, although some may be weeds of field crops. Hop Trefoil, however, is a small plant which causes little damage in fields. Light-seeking, it is a typical plant of stubble, but also grows in meadows, in ditches alongside paths, and in scanty hedgerows. It is usually found in poor soils.

Another small field species often growing in sandy and gravelly soils (but in warmer regions than Hop Trefoil) is Hare’s-foot Trefoil (T. arvense L.). It, too, requires light and is mostly found in stubble, although it also grows in sunny hedgerows even in quite acid soils. It is not generally present in limestone regions.

Both these trefoil species are native to Europe, temperate Asia, and North Africa, and both have been introduced to North America. At one time various species of Trifolium were used in the study of the autonomous movements of plants and their organs. In darkness the leaves are able to move within a range of as much as 120 .

T. campestre is one of the few yellow species of the genus. It grows to a height of 10 -30 cm. The flowers are borne on erect stalks in heads of twenty to thirty flowers which turn brown when spent. The flowering period is from June until autumn for plants which have germinated in spring; or only in spring for plants which have germinated the previous autumn. This, then, is an annual or overwintering plant multiplying only by means of seeds.

T. arvense is called Hare’s-foot (sometimes Cat’s-foot) Trefoil because of the thickly haired calyx (3). It is this which, after the fading of the white or pale pink flowers, makes the dead flowerhead look like a small tuft of whitish fur. This species is also an annual or overwintering plant.

Milfoil is an interesting plant of the composite family. The flowerheads are not numerous. They usually consist of only five strap-shaped florets and a greater number of tubular florets, and the fruit is an achene.