GARDENING / Power flowers: A hand-picked guide to hardy perennials: 7: Penstemon

PENSTEMONS are related to foxgloves and snapdragons. The large showy sorts, popular for bedding in Edwardian gardens, are not reliably hardy. They are still grown, but the best ones for staying power are smaller and tougher.

'Garnet' has the strongest constitution of all the Penstemons. Ribena-red flowers appear on bright green narrow leaves from midsummer until the frosts come. In a very hard winter it will die back to the ground, but should spring again from its base next year. 'Garnet' is good in mixtures of dark reds and pale pinks. Try it behind leaves of purple sage under fat pink roses. Interplanted with blue catmint and green alchemilla, 'Garnet' would provide enough colour for an original summer bedding scheme that lasted for years. But you would have to keep an eye on the companion plants, whose territorial imperatives are strong.

'Evelyn', at just over a foot in height, is almost half the size of 'Garnet'. Its tiny foxglove-like flowers, pale pink on spreading green bushes, are more delicate but just as prolific. Small enough to look good in a window box but colourful enough for the front of any flowerbed, this plant will keep going all summer and should survive a normal winter. Like most Penstemons it will maintain a green presence in the garden until it starts to flower again, and the fine leaves are an attractive bonus while the plant is resting. 'Garnet' and 'Evelyn' might look good in a bed devoted solely to them, making a sea of pink bells interrupted by taller red ones. Or 'Evelyn' might be added to a planting of the purple-leaved bugle 'Catlin's Giant', which has bright blue flowers. This would be a showy affair for a few weeks while the bugle's flowers were out; later its shiny purple leaves would be cheered up by the pale pink and indefatigable 'Evelyn'.

Some Penstemons come in changeable blues. Glaber is like shot silk, now pink and now blue, so you can include it with blue and pink-flowered plants. Lower than 'Evelyn', this one spreads and sprawls, flowering for months on end, from late May until autumn. 'Sour Grapes' looks blue one day, purple the next, but it is sensitive to hard frosts. 'Heavenly Blue' is tougher and shorter; another sideways spreader, it has lavender-blue flowers which would look well with a group of 'Jackman's Blue' Ruta or among the leaves of Iris pallida dalmatica. This iris flowers early, but its leaves look handsome all summer, so it would be a good foil for the later-flowering Penstemon.

Penstemons are not long-lived, but like many fast-growing perennials they root easily from cuttings taken in late summer. Half a dozen cuttings around the edge of a pot filled with gritty soil can sit on a cool windowsill or under a frame out of doors all winter. Given a burst of growth in spring (which means potting and feeding from about mid- March) they should make small plants, flowering the same summer, then get bigger, especially if you feed them.

Most power flowers are in their prime as young plants, but should give you a couple of years of good flowering before they start to decline. Regular renewal need not mean a trip to the garden centre and a call to the bank manager.