Top sedums for designers
Sedums are excellent at bringing a perennial planting scheme together, says Sarah Morgan
Beth Chatto has called sedums one of her ‘peacemakers’; as important a component in planting design as far more flamboyant plants. Why? Because “too many star performers lumped together can become quarrelsome”. It is no surprise, then, that there are lots of sedums in the Beth Chatto gravel garden, where only drought-tolerant plants are allowed. By sticking to these strict ecological principles, her garden team combines totally different species from around the world with awe-inspiring creativity.
Sedums are your classic drought-loving perennials with fleshy, succulent foliage emerging from ground-hugging rosettes in springtime. They have a knack of making a messy group of perennials look cohesive. They stabilise lively colours such as orange dahlias, or act as a contrast against silver-leaved ballota or lavender.
Designing with sedums
You can get them in lots of pretty tones of green, with varying undertones of blue, grey or red, or fashionable dark purple. Their late-summer flowers are one of the garden’s last hurrahs and omit a warm red glow in the failing autumn light – effective among spent brown Echinacea seedheads or yellowing Cornus foliage.
Dave Ward, Garden & Nursery Director at the Beth Chatto Gardens uses some clever design techniques such as planting a clump of three or five S. ‘Red Cauli’ AGM; then, just a little bit away, one on its own, as if nature had a hand in the design. “I know the trend is to grow them in blocks, but sometimes it’s nice to have a single plant. Essentially, sedums like a bit of space as it shows off their foliage. We often use the Chelsea chop (a pruning technique that coincides with the show), which also makes them bushier,” says Dave.
“We use low plants at the edge of a border, and plant taller sedums, such as S. telephium ‘Purple Emperor’ AGM, to the front. We then underplant with low-growing Gypsophila ‘Rosenschleier’ or a carpet of thyme.”
Best sedum for long-lasting interest
“One of our favourites is S. ‘Herbstfreude’ AGM, because it’s so long lasting,” explains Dave. “We love to plant it with big-leaved Bergenias or fine-leaved plants such as grasses, and don’t cut its stems down until January.”
Best sedum for walls and crevice gardens
There are plenty of smaller sedums that grow naturally in rocky crevices or along the coast in northern temperate regions and are charming grown in cracks in stone walls. They are also freqeuently used in green roof mixes. At the Beth Chatto Gardens, for instance, they grow many in the scree garden or around the base of taller plants in the gravel garden. “A lot of them are semi-evergreen so you get the additional benefit of winter foliage,” says Dave. “My favourite is S. spurium ‘Green Mantle’, as it forms a lovely creeping carpet of bright green that we can grow grasses through.”
Prettiest sedum cultivar
Nurseryman Billy Carruthers of Binny Plants believes “the prettiest one is S. ‘Aquarel’,” he says. “You have to see this to really appreciate how beautiful its foliage colour is – grey-green suffused with red. It’s a little bit floppy, but it’s a wonderful plant that just looks lovely throughout the seasons, and stands 50cm tall.”
Best sedum for combinations
As a foil for other plants, Billy recommends S. ‘Matrona’ AGM. “It has been around for a while, yet it’s still one of the best, as it has incredible foliage. It received top choice in the RHS Wisley trial. It’s a good neutral colour that starts off grey-green, but, like a lot of them, gets darker as the season progresses. The stems are thick but it doesn’t flop when it gets to its peak flowering time.”
Most delicate sedum cultivar
The most dainty of all the cultivars, according to Billy, is S. telephium ‘Red Cauli’ AGM. “It’s a real gem, 40cm tall, with small red flowers like miniature broccoli and blue-green foliage. I like it planted slightly back from the edge of borders. It’s not very floppy, but it has quite thin stems and, being less robust, is good supported among other plants.”
Best sedum for dark foliage
The best for dark foliage is S. telephium ‘Karfunkelstein’ AGM. “I’ve really loved this ever since we got it from Ernst Pagels years ago. It’s perfect and I’d make it my first choice in my own garden. Dark plum leaves are all the rage, and as this is a stronger plant than S. ‘Purple Emperor’, it stays more upright. As the season goes on the foliage gets darker and darker, finally turning to mahogany.”
Best new sedum variety
There are some newer varieties worth trying. “S. ‘Herbstfreude’ AGM is a really popular one that’s been around forever, but there’s another very similar one that we sell a lot of – S. ‘Veluwse Wakel’. It stands 70cm tall and has slightly tinted reddy leaves and good purple flowers that we think are better.”
Top sedum growing tips
Sedums are sun-loving, drought-resistant succulent perennials that grow in well-drained, even poor soils. You can grow the larger ones in more fertile soils. As sponges to water they just grow bigger and the weight makes them topple outwards. To make the plants bushier use the Chelsea chop, cutting growth back by half or more in May. They will flower a few weeks later.
Every four years or so, dig up the taller sedums and divide them, discarding the older outer growth. Powdery mildew can be a problem and is treated with a fungicide. There’s also the Sedum ermine moth that forms a communal web over plants that protect larvae, busy eating the foliage. Damaged stems can be cut out and webs removed and burnt. Sedums are valued as a late-season nectar plant for birds and bees. In the RHS Wisley trial the best for nectar were S. spectabile cultivars, but the ever-popular S. ‘Herbstfreude’ AGM was amongst the poorest.