Andrew McIndoe extols some of the magic ingredients of summer planting

I love all shades of purple in the garden, from the palest lilacs to the deepest plums. As spring turns into summer, these colours abound.

Splash them lightly, or daub them liberally through the border, for they mix well. The easy-to-live-with habits of these soft and rich hues accounts for a good deal of the popularity of some of our favourite garden plants: heucheras and alliums to name but two.

I often extol the virtues of heucheras, especially for their near-evergreen foliage: such a useful mainstay in the winter garden. The best of the bunch, Heuchera "Plum Pudding", is worth considering to add substance and depth to summer container planting.

A single plant will make a dramatic display in a pot when teamed up with a few deep pink or purple impatiens. For the more adventurous, try the deep rich tones of the heuchera with orange marigolds and a shocking pink geranium. The dark purple foliage of the heuchera will easily link any clashing colours together.

Of late, the choice of foliage plants for summer container and basket planting has increased far beyond the realms of nepeta and helichrysum; mainstays of the traditional hanging basket. Foliage colour is much longer-lasting than that provided by flowers, and with summer containers lasting well into autumn, it is all the more worthwhile.

Variegated foliage adds variety and golden foliage lifts the planting, but dark foliage adds drama and impact. Red-purple iresine, coleus and perilla are all worth looking out for, but the ravishing Ipomoea "Blacky" is the best new purple foliage subject.

With sleek, dark, elegantly-shaped leaves, it drapes itself elegantly over the edge of a pot or basket. Try growing it with the pretty, fragrant Nemesia aromatica. There are a number of different colours available of this excellent summer subject, including some very pretty blues and mauves.

Early summer sees the appearance of some of our most spectacular herbaceous perennials. Peonies and poppies are the darlings of the late May-early June border. Red poppies grab the attention, but can be hard to place, their bright colours screaming for attention.

Of all the oriental poppies, "Patty's Plum" is the best mannered. Soft, grey-mauve blooms unfurl from furry green ruffs atop stout, upright stems. It sits happily alongside most other colours, but is perhaps loveliest against silver leaves or the dark purple foliage of a shrub such as cotinus or berberis.

Lysimachia "Firecracker" is one of the most useful border perennials. Its deep wine-coloured foliage emerges in late spring, the shoots reaching 30cm by early summer. Like the heuchera, it is a wonderful plant to mix in the border, particularly with acid-green euphorbias and blue geraniums.

Planted with roses, astrantia and nepeta it helps to maintain interest when the first flush of roses has faded. Left to develop, it produces yellow flowers in mid-summer. I cut it back to 20cm when the flowerbuds appear, allowing it to produce a new flush of red-purple leaves.

I always wish the allium season went on for longer - they are such useful additions to any planting scheme. The amazing spherical heads of the larger-flowered varieties add a totally different shape and light vertical height which lifts more horizontal subjects. They are often planted with silver foliage plants, but are rarely out of place as long as surrounding plants hide their rather unsightly fading leaves.

Allium christophii (syn. Allium albopilosum) is one of the best and most enduring. The soft, silvery lilac flowers develop into large sparkling heads on 40cm stems. As they fade, the green seedheads persist in the border, changing to parchment and often lasting well into autumn and winter.

The curious Allium spaerocephalum extends the season, opening its drumstick like flowers on long slender stems after most ornamental onions have faded. The colour is rich red-purple and the compact flowerheads are striking when planted to rise above pastel annuals such as nigella, cosmos, or clarkia. Alliums are usually planted as dry bulbs in the autumn, they are one of the magic ingredients of summer planting.

Those on well-drained soil will have no difficulty growing Cerinthe major "Purpurascens", the broad bean flower. This wonderful plant sometimes overwinters, but more usually regenerates from self-sown seeds. The foliage is a lovely sea-green shade and the bracts at the stem tips shimmering purple around tubular purple and soft gold flowers.

Cerinthe can be raised from seed and grown in pots using a loam-based compost with added grit; those on heavy soil will find this more successful than planting in the open ground.