Sedums or stonecrops are succulents that make the perfect carpet in difficult stony spots in the garden where there’s very little soil. They soften the edges of a bed by colonising bordering slabs and will romp along drystane dykes or walls. They’re also used in green roofs.

I’m looking here at low-growing sedums, those gorgeous white, pink or yellow mats we see just now. Three species, Sedum acre, S. anglicum, and S. villosum grow wild in Scotland and together with modern cultivars are available to gardeners. So if you’re fired to get some yourself be sure to choose low-growing ones, not the taller autumn flowering plants that are officially classified as Hylotelephiums.

It’s safest to go to a garden centre where you can see what you’re buying or a specialist nursery like Simply Succulents. Online images of plants often focus on the flowers so check out flowering time and height as well.

Sedums are succulent, often evergreen, plants that naturally grow in rocky, exposed sites in thin soils, often in the mountains. They do not compete well with taller plants in fertile ground.

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Stonecrops, S. anglicum and S. acre have been seen in Ayrshire earlier this month. The former, found on cliffs, with clusters of tiny pink-tinged flowers, thrives in acidic soil, so is perfect for much of the western half of the country. Meanwhile, the yellow-flowered S. acre was seen in shingle at the back of a beach.

With its mass of pinky white florets, S. villosum, is a long-established Borders resident. It prefers wetter sites where it grows in damp flushes and on burn sides among the hills, but like all sedums needs open sunny places.

I inherited some stonecrop, Sedum album, on dykes and in dry, shallow beds and it’s been extending its pretty little empires, including softening a dull, orderly slab path.

It’s worth stressing that stonecrops needs a little soil, so if you have a mortar wall you would need to use pots. You could also place one on the ground. Start the plants in shallow terracotta pots. Mix a generous amount of grit with compost and place the pot at the edge of a bed. The pot gives a plant some extra light to absorb the sun and prevents competition from neighbouring plants. Before long it will clamber out of the pot and cover any nearby pathing.

So how can stonecrops cope with so little water? As well as storing moisture in their fleshy leaves they photosynthesise differently to most plants by absorbing CO2 from the atmosphere during the hours of darkness. Then they open their stomata and absorb CO2 and moisture from the slightly humid atmosphere. They close their stomata at daybreak thereby retaining, rather than emitting precious liquid through evaporation and use the retained CO2 to photosynthesise in sunlight.

Mangetout Pea 'Shiraz’Mangetout Pea 'Shiraz’ (Image: free)

Plant of the week

Mangetout Pea 'Shiraz’ bears dark purple pods that are easy to spot amongst the foliage, making picking quicker. The flowers are light purple and bluish and are very decorative.