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If you're wondering how to grow dahlias, then you've come to the right place. After falling out of fashion for a while, these beautiful blooms have staged a big comeback and their newfound popularity shows no sign of waning. After all, these incredibly varied plants offer something for everyone.
Dahlias are totally versatile, too – you can plant them in borders, grow compact cultivars in containers, or treat them as a cutting-flower crop for show-stopping displays indoors. They can also be very good value for money – a single dahlia tuber can produce blooms from the middle of summer right through to the first frosts.
Whether you want to fill your flower bed ideas or just test out one or two varieties of these stunning blooms in pots, they're a fail-safe option for gardens big and small.
'Anyone who grows dahlias will know they start flowering in mid summer but are at their best during late summer and fall, delivering masses of bloom right up until the first frosts,' says Amateur Gardening's Anne Swithinbank. 'Originally from the uplands of Mexico and the narrow strip of countries where North and South America connect, these equatorial plants enjoy plenty of sun, cool weather and hit peak performance when the hours of night and day are similar. Plant dahlias and you will have a brilliant late show in the garden and masses of blooms for cutting.'
Dahlias, which grow fresh from tubers every year, aren’t very good at pushing up through herbaceous plants. So, if you're growing them in a garden border, it's best to give them their own bit of space.
However, there are also some that are perfect for growing in pots as part of your container gardening ideas. These will look stunning lining a path or for a striking patio display.
'Planting tubers around 4-5in (10-12cm) deep in prepared ground during mid spring is the most straightforward method,' says Anne Swithinbank. 'Remember though that dahlias dislike crowding and need space to develop. If you want earlier flowers, plant tubers in pots under glass in early spring for planting after danger of frost.'
Garden expert Tamsin Hope Thomson for Amateur Gardening shares her top tips for planting dahlia tubers:
'Growing dahlias from seed is a great way of enjoying plenty of plants cheaply and easily,' says Anne Swithinbank.
'To grow flowers from seed, sow seeds thinly and evenly in spring, cover very lightly with compost or vermiculite and germinate at 65˚F (18˚C). Transplant seedlings singly to pots, grow on and plant outdoors in late spring or early summer. Go for something like ‘Bishop’s Children’, which delivers a pleasing mixture of single flowers against dark foliage, plus you can save the tubers of favourite colors.'
Dahlias are tender plants, so it's important to keep them protected from frosts. Because of this, it's generally best to start tubers off undercover in your greenhouse, or even a DIY cold frame in early or mid spring. Then plant them out once the temperatures outdoors are reliably warmer – generally around late spring to early summer.
Remember to harden them off before planting, by standing the pots outside in the garden for a week or two so they can gradually acclimatise to the outdoor conditions.
The beauty of dahlias is that they're not overly demanding, so can be added to your plot as part of your low maintenance garden ideas. However, they do require the right care at the right time to keep them happy.
During the summer and early fall months you will need to water them regularly throughout dry spells. Remember to feed them, too.
Don't be afraid to cut flowers off for displaying indoors because this will actually help your dahlias. Regular picking encourages them to keep on producing flowers – what a win! Deadheading flowers regularly is also advised, plus make sure you check for pests and signs of other disease.
Some dahlias are taller than others, which means they'll need a little more support to stop them from toppling over. It's worth knowing these tips:
Gardening expert Ruth Hayes of Amateur Gardening shares her step-by-step tips for taking cuttings from dahlias.
As with all flowers, taking cuttings from plants is a fantastic way to get new plants for free – ideal if you're after cheap garden ideas.
To get good, long dahlia stems and larger (but fewer) flowers, cut off all side growths 24in (60cm) below the growing tip. This allows plenty of stem for cutting these if you want to arrange them in vases indoors. And it also allows lower shoots to go on growing to produce replacement stems.
Another tip to ensure show-stopping blooms is to retain just the top bud and pinch out all the other flower buds immediately below.
'In colder regions and for ease of management, it is best to lift tubers after foliage has been blackened by the first frosts,' says Anne Swithinbank. 'Dry and store them frost free covered by slightly moistened old compost or sand.'
Tamsin Hope Thomson for Amateur Gardening offers these step-by-step tips for storing dahlia tubers:
If you're in a warmer part of the world then you don't have to lift the tubers. 'In milder regions dahlias can withstand most winters in the ground under a dry mulch of leaves or bark,' explains Anne Swithinbank. 'However, they might be late into flower and sometimes large, old tubers lose vigor.'
If you're going to leave tubers in the ground, the best method is to simply cut back the plants and then apply a layer of mulch or compost to the crowns for extra insulation. Our guide to mulching has more info should you need it.
As with most plants, a few pesky problems can arise. Here's a few to look out for:
In summer it's easy to get hold of potted up dahlias that are already in full growth. Alternatively, in spring, you can buy bagged up tubers from garden centers or online.
You can also pre-order tubers and rooted cuttings from specialist nurseries for an early spring delivery. However, make sure you've got a frost-free place like a greenhouse with heating or use insulating fleece when starting them off, depending on how cold it is.
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