Herbaceous clematis,
These non-climbing beauties are a boon to any border, clambering over their neighbours, spilling from raised beds and tumbling on to paths
Trends, flowers and colours may divide our tastes in the gardening community but very few plants have the universal admiration and enduring popularity of the much-loved clematis. The plants have such wide-ranging appeal, originating from a broad and diverse group of nearly 300 species. The genus Clematis has been planted and cultivated in English gardens since the 16th century and belongs to the Ranunculaceae or the buttercup family, alongside border stalwarts such as delphiniums, anemones and thalictrums.
Every family has its divas and if we put the large-flowered – and, dare I say, temperamental – attention-seekers to one side for a moment, I would like to explore the easier-to-grow, generously flowering and endlessly rewarding herbaceous group.
Lacking tendrils to cling as they climb, these clematis need support, and will happily scramble through either a birch or a hazel-clad dome, or through a neighbouring shrub. The shrub Physocarpus opulifolius ‘Diabolo’, for example, is a useful, rich-purple foil for other plants, but now let’s imagine it with the violet-blue flowers of Clematis ‘Arabella’, popping all over its foliage, and suddenly it has been elevated to another level of interest entirely.
One noteworthy species in this herbaceous group is Clematis integrifolia, from which has been bred an extensive number of cultivars and hybrids. It is used extensively in hybridising for some beautiful, award-winning plants such as C. x durandii, which is a cross between C. integrifolia and C. ‘Jackmanii’. These plants make lovely additions to a herbaceous border, either by the way of a vertical accent, as groundcover or perhaps cascading over the edge of a raised bed. They’re poster plants for the cottage style of gardening.
Another species of this group that I would like to draw your attention to is C. heracleifolia. Introduced into cultivation in 1837 and known as the hyacinthflowered clematis (how could you not be intrigued?), C. heracleifolia and its various cultivars all have their own, unique allure, and provide a good burst of colour, as well as an attractive source of nectar for butterflies, towards the end of the summer when other plants are starting to dwindle. Some may argue that the percentage of leaf to flower, compared with their more extravagant cousins, could be criticised; I say embrace the more naturalistic balance, cut a few stems for your kitchen table and prepare to be converted. Renowned plantsman Christopher Lloyd echoed the joy created by the scent of these clematis, along with others in this group, when he wrote in his 1977 book Clematis: ‘Vanilla, hot chocolate, almonds, lemons, primroses, cowslips and violets: all of these and other essences are wafted towards us on a light and teasing current of air so that we stop in delighted perplexity and seek out the cause with exploratory eyes, looking up and down and around about us.’
The advice of keeping the tops sunny and the base cool may be crude, but it is very apt for growing the majority of clematis. If fertile, moist and freedraining soil frustratingly eludes you, why not try growing clematis in a container? A good-sized, deep pot is ideal, filled with a mixture of peat-free compost and John Innes No.2, say 50:50, with a few handfuls of grit. Just add a 5cm layer of grit on the top and a fortnightly potash feed during the growing season and you’ll have a winning formula. Clematis pruning can baffle and may deter some from growing these plants but the unadulterated joy that characterises this selection of clematis is that their treatment could not be simpler: as they flower on their current year’s growth, they need to be cut down to just above the ground each spring as their buds begin to swell.
These gorgeous, herbaceous clematis offer us an easy win – simple to look after and care for, extending the season of our shrubs and borders, and flowering late on into the mist-filled autumn. All they ask of us is a few pea sticks or a shrub through which to scramble. I don’t think that’s a bad deal at all.
• Tom Brown is head gardener at West Dean Gardens near Chichester in West Sussex. His recommendations for the best herbaceous clematis can be found over the next five pages.