Plants which look good together

imageVal Bourne picks plants which are good together, like this hazy study in mauve works well with dewy mornings and low autumnal light .Combinations that peak in late September and October, when John Keats’s season of “mists and mellow fruitfulness” is providing dewy mornings and gauzy light, are an excellent idea.

This trio of plants catches the gentle, slightly decadent mood perfectly. The aster and the sedum make a strong contrast in form, the aster by providing a graceful haze of lavender-blue flowers, the sedum with its stocky, dark silhouette. The effect is blurred and softened by the penstemon that threads around and between them.

Late show

Aster turbinellus is wiry and self supporting, and the blue-green foliage adds to the soft blue-grey haze. Flowers, which measure less than an inch across, tend to lower their petals slightly, adding even more grace to the border. Known as the prairie aster, it grows on drier soil in the more southerly states of North America. There it’s found in grassland, woodland clearings and edges, thinly wooded slopes, cliffs, rocky glades and roadsides. As a result, most gardeners can grow this drought-resistant aster even when they have failed with others.

However, there are two forms commonly offered by nurseries. The correct form has blue-green foliage that clasps the stem in a sheath-like manner. Old Court Nurseries (see suppliers) sells the right form. Other nurseries sell a darker-leaved hybrid.

Plants that have an airy, delicate presence need a substantial partner and the dark stems and neatly crimped foliage of Sedum ‘Purple Emperor’ are perfect. By July this sultry sedum is topped by starry, bright pink flowers long before the aster buds appear. The smooth foliage is wine red from the moment it leaves the ground in spring, whereas many others only colour up as summer wanes. The flowers of ‘Purple Emperor’ (which are highly attractive to bees, butterflies and other insects) gradually fade to chocolate brown. This sedum also tends not to divide and flop in the centre as the clumps mature, a trait of many.

Finally, add a touch of opalescence with Penstemon ‘Mother of Pearl’, arguably the penstemon with the longest flowering season of all. This vision of pale pink tubular bells, held on the usual 2ft-high spike, would be nothing without the prominent purple veining that extends along the length of the inner flower. These inky striations link the eye to the foliage of Sedum ‘Purple Emperor’ and the outer pearly pink tube catches the soft cloud provided by A. turbinellus.

Alternatively, you could use the tender salvias ‘Waverley’ (or the slightly taller ‘Phyllis’ Fancy’) for a similar opalescent effect. Plant next year in early spring, not now (both are S. leucantha hybrids from Dyson’s Nursery at Great Comp in Kent (01732 885094; www.greatcompgarden.co.uk).

How to grow

All three plants need fertile soil that is well drained in winter and all do best in open, sunny situations, providing interest and flower from July until the first frosts. Staking is not required.

Aster turbinellus
This robust aster can be left to its own devices to develop into a large, tight clump. As the tallest plant, it should be planted at the back, either as a single specimen or in a drift of three, five or more. You may wish to leave the thistledown heads for winter effect, or you can cut them back to prevent seedlings. Divide asters in spring as they race into growth. Pot-grown asters planted now will settle in well and flower better next year (5ft). The clear blue, more upright ‘Little Carlow’ and the almost horizontal, mauve-pink ‘Coombe Fishacre’ also give leaf, bud and small flowers.

Sedum ‘Purple Emperor’
Spotted as a seedling by Graham Gough of Marchants Hardy Plants in 1993, this excellent, perfectly poised sedum is lovely from May until October. It fades beautifully into winter and persists from year to year, making well-behaved clumps. Widely available and can be planted now.

Penstemon ‘Mother of Pearl’
Plant in spring or early summer in a warm, sunny position. Take cuttings between June and August as few penstemons are completely hardy; they are also short-lived. Cut down in April after the last frosts. Deadhead regularly to encourage flowers.

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