Dahlias lend themselves to a broad swathe of garden styles from carefully coordinated colour schemes to the eclectic symphony of a traditional cottage garden. A diverse genus, they range from compact container varieties to tall feature plants for the back of the border. It's no surprise that they’ve experienced something of a renaissance in recent years.
Growing dahlias isn't as difficult as you might think - read on for top tips or browse our full range of dahlia tubers to choose your favourite varieties.
Dahlias can be raised from seeds, tubers or plug plants. Tubers are by far the most popular, and these mature, bare root plants are ready to go directly into the ground from mid-April, when the soil has warmed up a bit. Alternatively, they can be potted into large 3-litre pots and grown on in a frost-free greenhouse, before planting out into their final positions.
Plug plants are a little more delicate, requiring potting up and growing on in frost-free conditions during spring. They can be hardened-off and planted out in May once they’re well grown.
If you have greenhouse space or a bright windowsill then bedding dahlias are easily grown from seed. This is a cost-effective choice if you require large numbers of plants. Sow them from February to April in free-draining seed compost, maintaining a steady temperature of 18-20C. When they’re large enough to handle and have a well-established root system, transplant the seedlings into individual cells or small pots. Grow them on in warm conditions, repotting when necessary, until they’re large enough to be hardened-off and transplanted outdoors in late spring or early summer.
Dahlias are half-hardy, so it's important to keep them protected from frosts. Once all risk of frost has passed, they can be acclimatised to outdoor temperatures over 7-10 days before being planted out into their final flowering positions. Choose a sunny spot in moist, fertile, well-drained soil. Prepare the soil by digging in plenty of well-rotted manure or compost and incorporate some blood, fish and bone fertiliser to feed the plants.
Dig a hole large enough to accommodate the rootball, ensuring that your plant sits at the same depth in the soil as it was in the pot. Tubers should be planted so that the stump of the previous year's stem sits just above ground level, with the 'sausage-like' tubers covered completely by the soil.
Taller varieties will almost certainly need staking with sturdy canes or narrow wooden posts to support their stems. It's a good idea to insert stakes into the planting hole before positioning the plant. This will avoid damaging the root system later on. Settle the soil after planting by giving it a good soaking with water.
At this stage, it's a good idea to put some slug protection in place. Use copper tape to protect container-grown plants. Dahlias planted directly into the soil can be protected using slug traps, pellets, or physical barriers with rough surfaces such as a mulch of bark chips, crushed eggshells or sharp grit.
Here are a few tips to help you grow bushy plants with lots of healthy flowers:
In very mild areas, it may be possible to leave your dahlias in the ground over winter. Be sure that the soil is very free-draining and cover them with a thick layer of a dry mulch such as bark chips or straw. In colder areas, dahlia tubers can be lifted in autumn and stored over winter in trays of peat or sand. Just keep them in a cool but frost-free position. Here's how to go about it:
With so many different colours, flower forms and sizes to choose from you may find it hard to narrow your choices down. Be bold and create an entire dahlia bed - don't be afraid to experiment with extraordinary colour combinations for an exotic riot of colour. For a more refined display, try picking just a few colour coordinated varieties that can be repeated through mixed borders.
Discover more dahlia advice, such as how to deter pests, by visiting our dedicated page of dahlia resources.