10 award-winning (AGM) plants for clay soil

If you’ve ever got your boot stuck in the mud on a country walk – well, just imagine a whole garden full of the stuff. 

Thick clay soil can be made more manageable by adding plenty of organic matter, improving drainage, making raised beds and other tried-and-trusted techniques, but growing the right plants is a big part of successful gardening on clay soil, and some plants are perfectly well adapted to the conditions it provides.

Here are 10 winners of the prestigious RHS Award of Garden Merit (AGM) that will grow better than most on clay.

A bronze mat

Evergreen ‘Catlin’s Giant’ forms a mat of large, glossy dark bronze-purple leaves

Ajuga reptans ‘Catlin’s Giant’ bugle succeeds on clay because bugle grows naturally on clay in the wild. It’s one of the larger varieties, with bold bronze leaves and upright spikes of rich blue flowers in spring. It makes an effective carpet, but is best split and replanted every few years. 20cm (8in). Hardiness rating H7.

Delicate and neglect

This rose’s delicate, pure white flowers belie its tough constitution

Many old-fashioned shrub roses grow well on clay soil, so Rosa ‘Blanche Double de Coubert’ is a representative of them all, as well as being one of the finest old roses in its own right. The semi-double white flowers are blushed in bud, highly scented, open over many weeks and develop red hips later. Best left unpruned but rejuvenated occasionally by cutting back hard. 2m (6ft6in). Hardiness rating H7.

An explosion of colours

This shrub has drooping clusters of small, tubular flowers, sometimes followed by black berries

Ribes sanguineum ‘Pulborough Scarlet’ is one the most dependable and most colourful of early shrubs. The long strings of deep red flowers sway and tremble in the breeze all along the previous year’s shoots. It appreciates full sun and pruning as soon as the flowers drop, and it can also be trained in a fan on a wall, perhaps with Clematis alpina growing through it. 2m (6ft6in). Hardiness rating H6.

Lovely vanilla fragrance

Its double creamy-white flowers appear in small clusters in early summer

Philadelphus ‘Manteau d’Hermine’ was one of the first shrubs I ever planted and I still remember enjoying its neat growth, double pure white, early summer flowers and lovely vanilla fragrance. Its compact habit suits smaller gardens and tight spaces, and its profusion of

A type of flower that has extra petals, often having a fuller appearance. Plants with double flowers are often considered more ornamental and showy than those with single flowers, though they are generally not as good for wildlife, having little or no pollen. Some plants naturally produce double flowers, while others may be bred for this trait. Examples of plants with double flowers include roses, sunflowers, dahlias, and zinnias.

Drooping beauty

Laburnum × watereri ‘Vossii’ is characterised by bright yellow flowers in drooping racemes

The best of all the laburnums, and the one usually offered, Laburnum × watereri ‘Vossii’ is a sterile

A hybrid plant is the offspring produced by cross-pollinating one specific cultivar with another different cultivar. This process of cross-pollination, rather than pollination between plants of the same cultivar, generally creates stronger, healthier, improved offspring, said to have ‘hybrid vigour’.

Centenary traditions

Helenium ‘Moerheim Beauty’ has slender green leaves on tall stems

This is a case where an old variety is still a good one. Helenium ‘Moerheim Beauty’ has been around for almost 100 years, but its fiery summer flowers, with their appealingly swept back petals, open red then mature to yellow and are an even richer red on the backs. Best in sun, divide and replant every two or three years. 1m (3ft). Hardiness rating H7.

Spot the Chinese bridge

This snowdrop reliably produces two flowers per bulb giving it a long flowering period in spring

Many snowdrops thrive on clay soil, especially if split and replanted when the clumps become crowded. Galanthus ‘Straffan’ is unusual in that every bulb produces two flower stems each season, one taller than the other and one after the other, so the display is extended significantly. The inner petals feature a very distinctive 'Chinese bridge' green mark at the tip. 12cm (5in). Hardiness rating H5.

The umbrella plant

Darmera peltata has glossy, rounded leaves that remember an umbrella

Darmera peltata is an easy

Perennials are plants that live for multiple years. They come in all shapes and sizes and fill our gardens with colourful flowers and ornamental foliage. Many are hardy and can survive outdoors all year round, while less hardy types need protection over winter. The term herbaceous perennial is used to describe long-lived plants without a permanent woody structure (they die back to ground level each autumn), distinguishing them from trees, shrubs and sub-shrubs.

Invasive success

Anemone × hybrida ‘Honorine Jobert’ might become invasive in clay soil

This lovely plant can succeed too well on clay soil and spread too much. But Anemone × hybrida ‘Honorine Jobert’ has bold, weed-smothering foliage followed by long season of pristine white, gold-centred summer and autumn flowers that makes it an essential in a sunny or partially shaded place on clay. Just be sure not to partner it with plants that will be overwhelmed. 1.2m (4ft). Hardiness rating H7.

Happy in clay

This plant is a slow-growing medium-sized tree of conical outline and elegant habit

Alder, Alnus glutinosa, is another British native that’s naturally happy on clay but for our gardens we can choose a variety that’s more attractive than the ordinary wild native type. Alnus glutinosa ‘Imperialis’ has finely cut, jagged foliage that gives the plant an elegant airy look, and the whole tree has a grace we don’t expect from an alder. Happy by water as well as on clay. 6m (20ft). Hardiness rating H6.