These heat-loving plants, with their vibrant colours and precision-cut petals, are once more a must-have in any garden.
A native of Mexico, the dahlia was introduced into Europe – to the Madrid Botanical Gardens, to be precise – in 1789 and, since then, the tuberous perennial has enjoyed wildly contrasting attentions. Dahlias need full sun and appreciate steady moisture and regular feedings until the flowers start to appear.
Here is everything you need to know about growing Dahlias.
Pictured, Dahlia ‘Citizen’ with classic euphorbia-like bupleurum.
The Victorians loved the blooms for their striking forms and colours and created great dahlia walks to advertise their extravagant employment of gardeners. By the late 20th century, however, the general flower-loving public had developed a love-hate relationship with the dahlia.
Pictured, Dahlia ‘Barbarry Sultan’; plant several together for a bold statement.
The dahlia’s blowsy colours, bushy appearance and high maintenance as a bedding plant were less suited to the more free-flowing garden styles that had developed. However, it found a new popularity with allotmenteers, lovers of cottage-style gardens and as a key feature of flower shows across the land.
Pictured, Dahlia ‘Floorinor’, an anemone dahlia, with green foliage. As it blooms until October, try it in a border with similarly shaped monardas and heleniums for late summer colour.
The recent resurgence of the dahlia was triggered by the late Christopher Lloyd, who confidently mixed bright dahlias through herbaceous borders. Today, Monty Don picks rich, bold shades for his Jewel Garden, while Dan Pearson admires the interplay of different flower shapes.
Pictured, Dahlia ‘Veracruz’; a mid-height decorative dahlia, it ties in well with violet and white colour schemes, so could be paired with white cosmos in late summer.
Eminently attractive to bees, dahlias have dark foliage that is an excellent backdrop to other shrubs and flowers both in the border and in bouquets.
Pictured, Dahlia ‘Waltzing Matilda’, a single dahlia in a rich sunset shade, is a lovely border flower that looks good with the foliage of a perennial such as Heuchera ‘Marmalade’.
Such is the revival of interest in the dahlia that it is now an essential ingredient in many florists’ designs, with the likes of Hayford & Rhodes and the late Jane Packer matching dahlias, for instance, with roses, hosta leaves and the pure white flowers and oak leaves of Hydrangea quercifolia ‘Ice Crystal’.
Pictured, Dahlia ‘Pembroke Levenna’; bred from Dahlia ‘Hamari Rose’ and another unknown parent, this ball dahlia is a showstopper for late summer with its bright pink head. Use in bold groups with other late summer flowerers.
While it is unlikely that the dahlia will ever again be as rampantly popular as it was with the Victorians, the plant’s extensive variety of form and colour, and its versatility as a cut flower, has enabled it to find a new fan base in the 21st century.
Pictured, Dahlia ‘Scaur Glen’, here with bupleurum.
- Dahlias like a free-draining soil and hate wet clay.
- Plant the tubers out between mid-May and June.
- Plant in holes 15cm deep and 90cm apart; drive in stakes now so as not to damage the root system later on.
- Dress with pelleted chicken manure or a general purpose fertiliser.
- Water on nematodes to prevent problems with slugs.
Pictured, Dahlia ‘Happy Single Princess’; with flowers that are four inches in diameter, the pure white of this dahlia looks lovely against dark foliage, such as Cotinus coggygria ‘Royal Purple’.
- Keep tubers well watered and feed every three weeks with tomato food.
- When plants reach 15cm tall, pinch out the apical meristems to encourage bushy growth.
- For late flowers, cut back the first growth to less than 30cm in early June.
- Deadhead twice a week.
Pictured, Dahlia ‘Ken’s Rarity’, a waterlily dahlia that likes an open position in full sun, where it will flower until late October.
- If your soil type is dry, tubers can be left to overwinter; lift if the soil is damp, as in Dorset, for example.
- Lift when the first frost has turned tubers black and forced all the sugars back into the tuber.
- Dig around the dahlia clump and lift tubers with a fork, taking care not to damage them. Stand them upside down to dry them out completely.
- Dust with fungicide, then store in a frost-free, dark shed, preferably in dry, spent compost, or covered with 3-4 inches of mulch.
- Protect with mouse traps as mice love to eat dahlia tubers.
Pictured, Dahlia ‘Magenta Star’, a single dahlia, it has been awarded the RHS Award of Garden Merit and is attractive to pollinators. It will flower from June until the first frost.
National Dahlia Collection, 07879 337714
Parkers, 0161 848 1100
Rose Cottage Plants, 01992 573775
Van Meuwen, 0844 557 1850
Pictured, Dahlia ‘Oakwood Firelight’; this shaggy semi-cactus dahlia would light up any dark border in late summer, perhaps set alongside salvias such as S. involucrata ‘Hadspen’.
Single – up to ten petals surrounding a central disk
Anemone – several rings of flattened petals around a more dense, central group of shorter, tubular petals
Collarette – single outer ring of petals with smaller inside collar of petals around the flower’s central disk
Waterlily – several rows of broad, curving petals and a flattish flower head
Decorative – broad, flat, full double blooms, with some curve but no central disk visible
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Pictured, Dahlia ‘Olivia’, a collarette dahlia with two tones of creamy yellow and purple-pink; clump-forming and likes a sheltered position. Regular dead-heading will ensure a long flowering season.
Ball – densely packed double flowers with slightly curved, rounded petals
Pompom – similar to ball dahlias but smaller and with petals that curve along their full length
Cactus – double-flowered dahlias with tapering petals and slight shaggy appearance
Semi-cactus – petals that broaden towards the middle of the flower and curve towards the tips
Miscellaneous – everything else, e.g. Dahlia ‘Bishop of Llandaff’
Pictured, Dahlia ‘Spanish Jewel’, a decorative dahlia which is a stand-alone plant for impact in a prominent place in the border.
Collarette Dahlia ‘Carstone Firebox’ is a warm orange colour, as its name suggests, and will look good planted near trees as their foliage begins to turn in early autumn.
Dahlia ‘Pearl of Heemstede’, a waterlily dahlia, grows to three feet in height. With its silvery pink flowers, it makes an ideal container plant, matched with grey Helichrysum petiolare ‘Goring Silver’ to trail around the edge of the pot.
If you liked this, find more gardening ideas on the Homes & Gardens website