Horticultural lecturer Louise Danks lead the rescue of the National Dahlia Collection, now homed in a grassy field in Cornwall owned by the Kehelland Trust. She has won gold medals for her dahlia exhibits at Chelsea, and has learned how to cultivate dahlias from two of the finest growers in the business - Mike Mann and Mark Tyening. Below she offers four key tips on how to care for your dahlias.
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You don't always need to lift dahlias, sometimes mulch is better
On the free-draining site at Kehelland, there is no need to lift the tubers. Instead the volunteers apply ‘stupidly thick’ amounts of a mulch made from recycled green waste - a generous six inches deep. As well as offering winter protection and improving the thin sandy soil, the mulch helps to preserve moisture through the summer. (The collection is never watered.)
Feed your dahlias
Dahlias are hungry, thirsty plants. Mulching will provide some nutrients, but look to add a higher nitrogen feed while the plants are in leafy growth, and after pinching out the tip of the main shoot. (This encourages bushier growth.) Then once the plants are in bud and flower, move on to something higher in potassium. While the plants at Kehelland are not irrigated, plants will benefit from regular watering, and it is vital for plants grown in pots.
Deadhead your dahlias
Pick (or deadhead) your dahlias regularly to keep them in flower: the more you pick, the more blooms you will get. It is easy, says Louise, to tell the spent bloom from the bud: the buds are round and the spent blooms pointy. Deadheading continues late into the year: ‘the later the flowering season the better for our pollinating visitors’. Then seeds are left to develop and harvested on dry autumn days.
Dahlias are easy to propagate
Dahlias, says Louise, offer a Propagation Masterclass. “You can propagate them in any way - by division, rooted cuttings or growing from seed, and they will reward you with flowers and tubers in the first year.” Plants grown from seed are unlikely to come true to the parent – but among your seedlings you may discover a splendid new variety!
Here's a planting pot design using dahlia for the garden