The Latin name of the genus derives from a word “sedo” – which means “to calm down”, “to subdue”. Fleshy leaves of stonecrops of several species have long been used as a natural pain-killer. It has also been mentioned in the specialist literature, that the genus name might derive from “sedeo” – meaning “to squat”, since sedums grow in low mounds, which look as if sitting on the ground. It is commonly thought, that these plants are very robust, able to survive without water and soil, however, this is only true for a half of sedums. Others prefer moist and fertile soils.
About 500 species belong to the genus, and most of them are native to the temperate climate zone and mountains of the Northern hemisphere. These are annual and perennial herbaceous plants, sometimes sub-shrubs with erect or creeping stems, which root easily. The leaves are fleshy, simple and varying in form. Flowers are tiny, star-like, white, cream, pink, red or blue, held in panicle- or umbrella-shaped racemes. Sedums look great throughout the summer, bet some of them turn sparse after flowering.
Depending on the flowering time, sedums are divided into early, medium and late flowering groups. Sedum acre, Sedum album, Sedum cyaneum, Sedum hybridum, Sedum kamtchaticum, Sedum rupestre, Sedum sexangulare), Sedum spurium all belong to the early-flowering group (June-July). Medium-flowering sedums (July-August) include Sedum maximum, Sedum ewersii, etc. Late-flowering or eastern (oriental) sedums (Sedum maximum, Sedum spectabile, Sedum ruprechtii) flower in August up to the killing autumn frosts.
According to the required growing conditions, sedums fall into two groups. The low-maintenance plants, which thrive even in the poorest of soils, belong to the first group. These are mostly low, mat-forming sedums. The second group includes sun-loving and tall sedums, which prefer fertile clay or sandy soils. If grown in the shade, they stop flowering and become straggly. They flower abundantly in fertile soil, and are tolerant of drought, but need an occasional watering. They should be divided every 4 to 5 years.
Sedums respond well to organic and mineral fertilisers. Apply a bucketful of compost or well-rotted manure, and they will reward you with even lushier growth and more abundant flowers.
Although sedums are fairly hardy, Sedum sieboldii, Sedum eversii and several other species should be protected in snowless winters, otherwise they will become rather unsightly by spring. However, they will resprout readily and bulk up soon. All sedums, depending on species, require regular dividing and transplanting every 3 to 6 years. In order to retain the spreading habit of Sedum ewersii, their blooms are best removed. These plants are easily overtaken by weeds, so they need regular weeding and tilling.
Sedums are propagated from seed, by division or stem cuttings. Cuttings are best taken in spring or autumn, and rooted in a cold frame or a special nursery bed. Tall sedums, especially those with hollow stems, root better in spring, while creeping evergreen sedums root equally well in summer. Sedums can also be propagated by tip cuttings in summer.
Seeds are sown in spring or autumn in trays either inside or in a greenhouse. Seedlings are tiny, and should be transplanted into beds or pots at the stage of 1 or 2 true leaves. They start flowering in 2-3 years, and can be divided in their 4-5 year.
The low-growing creeping sedums are easy to propagate by cuttings, since numerous bulbils form on the stems, which root as soon as they touch the ground. Not only the stem cuttings strike readily, but leaves also root well. If you need to produce a lot of plants, prepare a nursery bed. Dig over the soil, remove even the tiniest weeds, level off the bed and roll it lightly. Place the plants on the bed, and cover with a layer of mixture, made of garden soil and sand, then press lightly. Water well and keep shaded from direct sunlight in hot weather.
Generally, all of the cuttings planted 1-2cm deep in pots in the greenhouse or inside break the roots. They should be kept warm, but not too humid, and protected from direct sunlight. Species sedums are more difficult to root than the cultivars. In two weeks time, young plants can be moved to the flower bed. If planted out too late, they will grow straggly and will be harder to establish. This method of propagation is not suitable for Sedum ewersii and Sedum sieboldii, since their shoots can rot in damp soil. Their cuttings should be taken with longer stems, preferably with a part of rootstock attached, and then planted directly into the flower bed and shaded.
More of new plants can be produced in winter. Spent flower stalks should be cut down before the frosts, and placed on shelves in the greenhouse. Leaves fall soon, and new shoots start growing in their place. Remove the shoots, when they are 4 to 5 cm long, and pot them on. They root best at room temperatures. When short of light, shoots become leggy, and rot easily, if overwatered. Transplant young plants into the border in May, where they will flower in autumn.
Sedums of different species associate well in mixed borders. Plant low-growing spreading plants in large groups at the front. A variety of forms and colours of their leaves and flowers make for a nice effect. Small plantings of medium-sized sedums and the specimens of large sedums can be planted towards the back of the border. Low-maintenance spreading sedums are suitable to be planted on green roofs. They tolerate urban pollution, drought and heat; they also spread and multiply fast, rooting easily with hardly any soil.
© Giedra Bartas, 2009