• AGM plants

    AGM plants have been through a rigorous trial and assessment programme. They are:

    • Excellent for ordinary use in appropriate conditions
    • Available to buy
    • Of good constitution
    • Essentially stable in form & colour
    • Reasonably resistant to pests & diseases

Back in the days when alpines and rock plants were grown on rock gardens, trailing types were invaluable in hugging the rocks to hide their bulk and cascading down to create sheets of colour. Although times have changed and we now prefer raised beds, gravel gardens and large containers for our alpines. Luckily trailing plants are just as valuable. They can tumble over the edge of raised beds, creep across gravel mulch and make a verdant backdrop to small bulbs. Growing in cracks and crevices in stone or brick walls they’re superb. 

Here are ten trailing alpines, all of which have received the coveted RHS Award of Garden Merit.
 

Arabis alpina subsp. caucasica 'Flore Pleno'

A classy classic

Arabis is a classic May flowering alpine that anyone can grow. This double flowered form, A. alpina subsp. caucasica 'Flore Pleno' extends the flowering period compared to single forms, and adds a little class to the act. Spreading about three times as wide and high, the neat, grey-green, evergreen leaves make an ideal background for the pure white flowers and an attractive carpet for the remainder of the year. Height: 20cm (8in). H5.

Aubrieta 'Doctor Mules'Aubrieta upgraded

Another special form of an old favourite. The vivid flower colour sets Aubrieta ‘Doctor Mules’ above the more widely seen forms whose colouring is often rather pale and thin. The evergreen foliage spreads happily over sunny bank, trails from cracks in walls, or over the edge of a raised bed, and can spread to 50cm (19in). It is densely covered in flowers during April. Height: 10cm (4in). H5.

Aurinia saxatilisBushy and billowing

A slightly bushy trailer, the clouds of yellow flowers that cover Aurinia saxatilis in May are unusual in the richness of their mustard-tinted colouring. Billowing over the edges of raised beds, or even as a specimen in a terracotta pot, the hairy grey-green leaves make the ideal background. This is a resilient little plant, more like a twiggy little shrub than a traditional alpine. Height: 20cm (8in). H5.

Campanula poscharskyana 'Stella'Lovely on walls

Campanula poscharskyana 'Stella' is an easy, vigorous – sometimes too vigorous  alpine especially suited to cracks in walls. In fact, plant it at the edge of a raised bed and before long the shoots will be bursting through the wall lower down. The long trails of bright, violet-blue summer flowers are charming, and open over many weeks. Height: 15cm (6in). H5.

Dianthus gratianopolitanusRare British native

Dianthus gratianopolitanus is a rare British native, found only in the Cheddar Gorge, Somerset. It is a lovely evergreen, mat-forming perennial with slender leaves that create a harmonious background to the clusters of highly scented, deep pink flowers that open over many weeks in summer. Ideal planted to creep over a gravel mulch, in a sunny raised bed or well-drained soil. Height: 15cm (6in). H6.

Gypsophila repensVertical sheets of flowers

It’s not easy to create a striking vertical impact with alpines, but when the neat greyish-green leaves of Gypsophila repens, a mat-forming evergreen, reach the edge of a raised bed they creep vertically down the wall, hugging it close. For an unusually long period in summer, the tiny white or sometimes pale pink flowers cover the plant in open sprays. Height: 15cm (6in). H5.

Hypericum olympicumBright sunny flowers

Another of this selection featuring greyish-green foliage, Hypericum olympicum is a twiggy little deciduous plant spreading up to 50cm (19in). This is another summer-flowering alpine that has large, rather starry, deep yellow flowers with a bright sunny appearance. They also produce seeds that tend to germinate and spread the plant around the garden. Tolerates drought well. Height: 20cm (8in). H5.

Lithodora diffusa 'Heavenly Blue'Blue beauty

In May and June (and often earlier), the sparkling, deep blue, five pointed flowers of Lithodora diffusa 'Heavenly Blue' bring a colour to alpine plantings that is not often seen. This widely spreading, mat-forming, evergreen shrub has dark green slightly bristly foliage. Best grown in pockets of humus-rich, acid soil, it is also well suited for growing as a specimen in a container or trough. Height: 15cm (6in). H5.

Persicaria affinis ‘Superba’A star of autumn 

Persicaria affinis ‘Superba’ is an invaluable late flowering trailer from August to October; bringing colour to alpine plantings at a time of year when other alpines are long finished. An interlocking mat of reddish stems carry tightly packed, evergreen leaves, which develop bronze-brown tints in autumn. The 7cm (3in) long, upright, cylindrical spikes of small flowers open pale pink and becoming increasingly dark as the weeks pass. Height: 20cm (8in). H5.

Phlox douglasii ‘Red Admiral’Phlox are essential

The two creeping alpine Phlox species. P. douglasii and P. subulata, should be at the top of the list of trailing alpines and P. douglasii ‘Red Admiral’ serves as a fine representative of the six cultivars awarded an AGM. Phlox douglasii is the more compact of the two, spreading to 30-40cm (12-16in), the fresh green, evergreen foliage hidden in spring by a mass of rounded flowers, in this case in deep reddish-pink. Height: 10cm (4in). H5.

 

More information

Find out more about RHS Hardiness Ratings
Graham Rice: 10 AGM rock plants with good foliage
Graham Rice: Alpines for autumn

 

RHS Membership

Sign in

Exclusive for RHS members: listen to our regular podcasts with gardening advice from the experts

Sign into the RHS website to read more

Sign in

Get involved

We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.