The root of 3; Three plants that look good together: Tulipa 'Groenland' Euphorbia amygdaloides robbiae Cornus florida 'Rainbow'

This week's group of three is a class act for much of the year, but particularly outstanding in spring.

As a centrepiece, plant the North American Flowering dogwood - Cornus florida "Rainbow" - a choice shrub, compact and upright. Beneath it grow "Mrs Robb's bonnet", the Wood spurge - Euphorbia amygdaloides robbiae - a plant that is a lot less complicated than its name. Underplant with the Tulip "Groenland" - Tulipa "Groenland" - and, in spring, this group will light the garden in cool shades of fresh, lime green and greenish yellow.

The dogwood achieves this with its leaves, which are broadly oval, slightly curved, dark green and held with great poise. Throughout summer, their margins are golden, but when they first unfurl, apple green.

The Wood spurge echoes the colour with its flower heads of greenish-yellow bracts - typical of most Euphorbias - and the Tulip repeats it, because "Groenland" is a viridiflora (green-flowered) tulip. The whole effect is quietly stunning.

This is not the end of the performance. From late spring to early summer, the Flowering dogwood flowers - no surprises there. The flowers themselves are inconspicuous, but each is surrounded by four white, petal-like bracts, slightly curved like the leaves and the shape of squat candle flames. They have a prehistoric look about them.

In autumn, the dogwood marks the season with its leaves, which turn plum- purple and scarlet before falling. The Wood spurge keeps its handsome rosettes of shiny, dark-green leaves all year round. They form mounds a couple of feet high, making an effective and dark foil for the taller, paler flower clusters.

These flowers can look good for months, even after they have faded to brown, although they should be chopped down to encourage compact growth and new stems. Wear gloves for this job because the milky latex from cut leaves and stems is an irritant.

In late spring, the "Groenland" tulips will open their shapely, cup-like blooms above the heads of the Wood spurge. Some of the tulips in the viridiflora group are entirely green, but this one has a flame of green up the centre of each petal, which fades through cream-green to pale orchid-pink at the margins.

The dogwood prefers good soil - neutral to acid - and some sun. The tulip will be happy in these conditions, too. The Wood spurge will tolerate situations where few others will grow - dry, rooty soil in the shade - and it is often relegated to such sites. At the foot of the dogwood, it will be in heaven.