To call a plant ‘dependable’ sounds like damning it with feint praise. The subtext is ‘reliable, but boring’. There are lots of plants though, sedums amongst them, that are easy-going, hard-working plants that are comfortable in most gardens. They may not have firework flowers or extravagant architecture but sedums are beautiful from the first stirrings of early spring to the twilight of autumn. They are like old friends: you can rely on them without lots of fussing over and they lift the spirits whenever you see them.
Sedum ‘Bertram Anderson’ is typical of the unpretentious genus. In spring a mound of tight red buds push though the soil, followed by dusky-purple fleshy foliage during the summer and, finally, by deep red flowers in the autumn. At no time is it flashy, but at all times charming. ‘Bertram Anderson’ is low-growing with long stems that cover the ground. I grow it in wide and shallow clay pans with a plant of the same growth habit, Sedum cauticola. The deep red stems of ‘Bertram Anderson’ intertwine with the glaucous grey foliage of S. cauticola to create an eye-catching effect.
The genus Sedum contains over 400 species of succulent-like, waxy-leaved plants that, for the most part, thrive in dry, poor soils. Most are mat-forming, creeping along rocky-crevices in situations that other plants find hostile. Relocate such plants into the 5-star luxury of a British garden and they become thugs. It is tempting to introduce the yellow-flowered stonecrop, Sedum acre, into the crack of a dry-stone wall, but before long it will colonise the rest of the garden. There is a golden-leaved form, Sedum acre ‘Aureum’, that is often sold in garden centres as an alpine plant for pots on patios. It’s a thug; avoid it.
Sedum reflexum is also stoloniferous, creeping along the ground in the same way as Sedum acre, but is less vigorous and more controllable. The tiny blue-green leaves that whorl around its stems resemble plumped-up pine needles. The cultivar ‘Angelina’ has bright golden-yellow evergreen foliage that turns orange during the autumn.
Better-behaved than both these species is Sedum populifolium, which forms a dome 40 cm high of fresh green, crinkly-edged leaves that are smothered in loose sprays of soft-pink flowers in late summer.
The tight rosettes of Sedum spathulifolium are an essential element in carpet-bedding schemes. The plant is a compacted bundle of tiny, fleshy leaves that seem to be made from polished marble. Sedum spathulifolium ‘Cape Blanco’ has a ghostly grey sheen that glows in the evening light. The plant is at its best when it is not flowering – the bright yellow flowers are tiny but still jar with the foliage.
Sedum telephium is a British native that has spawned many attractive cultivars and hybrids. Sedum telephium subsp maximum ‘Atropurpureum’ has loose panicles of silvered buds and pink flowers that complement the purple foliage. Like most of the S. telephium cultivars it can be grown in part-shade. A decade ago the appearance from Europe of Sedum t. ‘Matrona’ rekindled an interest in herbaceous sedums. Its strong stems and leaves are dark green flushed with grey and purple, a very subtle colouring that does not jar with its pale pink flowers.
Sedum telephium ‘Red Cauli’ might not be the most attractive name to give a plant, but it does provide an accurate description. The tight red buds and flowers resemble miniature cauliflowers. It’s a very compact plant that never grows to more than 30cm tall. Another very recent introduction, S. telephium ‘Bon Bon’, is equally compact, with glossy chocolate foliage and small rounded flowers. ‘Red Cauli’ was selected by Graham Gough, who also introduced perhaps the best of the dark leaved sedums, S. ‘Purple Emperor’. Planted in bold groups, the glossy purple foliage is most impressive against the greys and silvers of Convolvulus cneorum and Ballota pseudodictamus or at the base of Miscanthus sinensis ‘Morning Light’. Mine grow through the felted white leaves of Buddleija cripa. Gough continues to make selections of sumptuous dark-leaved sedums at his nursery, Marchants, in East Sussex.
Nurserymen and plant breeders are introducing lots of new sedums at the moment – often with little difference between them. Thirty years ago the choice of herbaceous sedums was mainly limited to cultivars of the ice plant, Sedum spectabile. With larger leaves and stronger stems than S. telephium, S spectabile is a handsome plant that comes into its own when it stars to flower in late summer. The large flowerheads attract every bee and butterfly in the vicinity. S. spectabile ‘Brilliant’ may have been around for a long time, but that’s because its fresh green scalloped leaves and brilliant pink flowers make a startling impression. A plant with even brighter flowers was discovered in America amongst a patch of ‘Brilliant’. Named S. spectabile ‘Neon’, its screaming lipstick-pink flowers are not for the faint-hearted. There are several named white-flowered forms, with S. spectabile ‘Iceberg’ being the most popular. S. specatabile ‘Star Dust’ has darker foliage and slightly whiter flowers.
Several herbaceous sedums have variegated foliage. Like most variegated plants they have their supporters and their detractors. Personally, I find them difficult to place in the garden and the combination of cream and green leaves and pink flowers makes me feel a little queasy. Sedum erythrostictum ‘Frosty Morn’ has appealing clean-white and bright-green leaves, but then those pink flowers just ruin the effect. Plant breeders are attempting to produce a white-flowered sedum with white-variegated foliage. It’s a combination that sounds irresistible and, if it ever appears, could be a plant worth growing.
Every year a tempting sweetie-bag of glamorous new plants are introduced to gardeners. It’s so easy to be dazzled by novelty that we become blind to the great garden plants that we already have. Sedums are never on those lists of sexy plants, but they do make a more enduring contribution to the garden than a brief encounter with a Johnny-come-lately.
Sedums are easy to grow in full sun on poor, well-drained soils. Good drainage is essential to prevent them rotting during the winter. Avoid mulching with organic matter around the crown as this, too, can cause the crown of the plant to rot. Sedums are a magnet for vine weevils, whose nasty maggots burrow deep into their crowns. Chemical drenches are available to control vine weevil in the surrounding soil. The best remedy, though, is to dig the plant up, wash off all the soil from around the roots and replant elsewhere. Vine weevils are wily devils, so check carefully that none are hiding amongst the roots before replanting. Because they are such a problem many nurseries now only sell sedums that have been freshly propagated each year. If you are buying large plants that are several years old, check them for vine weevils first.
A potentially more serious threat to the plant comes from the caterpillars of the sedum small ermine moth, which quickly defoliates entire plants. The moth mainly affects cultivars of Sedum telephium and is sporadic in its appearance – some years disappearing from areas where it has previously been prevalent. There is no way to control it, other than cutting away and destroying the writhing cobweb-covered nests of caterpillars as soon as they appear.
Sedums are amongst the easiest plants to propagate. Stem cuttings taken in early summer that are inserted into a pot of gritty compost and kept out of direct sunlight will root in a few weeks. Even a single leaf, torn away from the main stem, will quickly produce roots in a well-drained compost.
Stopping the Flop
Sedums grown in rich soils grow quickly, producing long, weak stems that flop over under their own weight. Attempts to stake them invariably resemble bunches of trussed-up Brussels sprouts. If your soil is too fertile for growing sedums well, cut them down to the ground at the end of May, before flower buds begin to form. The resultant re-growth will be shorter and strong enough to hold the flowers upright. Some sedums are better at remaining upright than others. S. ‘Carl’ has brilliant rose-pink flowers and keeps its domed shape, never growing to more than 30cm tall however much the soil is enriched. Two recently-bred sedums have the same characteristic: S. ‘Picolette’, which has bronze foliage overlaid with a silver patina while S. Xenox. has green foliage with a waxy blue covering. Both are about 35cm tall and have dark red flowers in the autumn. Plant breeders are working to produce further new Sedums that are adapted to heavy, rich soils, so that more gardeners can enjoy growing them.