Each of this week's plants has a particular habit of growth and overall "look" that is very different from either of its two companions. None of the three grows to more than a foot off the ground, but all spread sideways a reach a good deal further. Planted together they will form a mosaic of contrasting shapes, colours and textures - catching the eye and smothering weeds all at the same time.

The genus Hebe (named after the Greek goddess of youth) contains about 100 species of evergreen shrubs. This one, Hebe pinguifolia "Pagei", is among the smallest. It has creeping, purple stems which are densely covered in small, rounded, blue-grey leaves, and in May it smothers itself in a froth of white flowers. It forms a sturdy, no-nonsense mound, not more than a foot high but perhaps three times as wide.

The Milkwort or Spurge, Euphorbia myrsinites, echoes the foliage of the Hebe with evergreen, blue-grey leaves of its own, but there the similarities end. This succulent-like perennial has long, almost prostrate, radiating, fleshy stems, around which its pointed leaves are arranged in a spiral. There is an almost animal quality to it. In spring, heads of bright greenish- yellow bracts, characteristic of so many of the Spurges, are produced on the ends of the stems.

The third and final plant in this group is a variety of the (lucky) Shamrock or White Clover. The Shamrock usually has three green leaves; this variety has four purple ones. Its botanical Latin name says it all - Trifolium repens "Purpurascens Quadrifolium". The repens simply means creeping, and it does, as far as you let it, for its stems root themselves as they grow.

It forms a carpet of foliage about 4in tall, but its impact is greater than its height. Each of the purple-maroon leaves stands out, for they are outlined with a green margin. It is a striking plant and an effective contrast to its blue-green neighbours. It has an airy nature and brings lightness and movement to the grouping.

If you only have room for one of each then that will have to do, but they are best appreciated in larger groups. All of them like plenty of sun and the Hebe and Euphorbia need soil that is well drained, particularly in colder and wetter areas of the country. A gently sloping bank or a large rockery would be ideal.