How To: Plant Dahlias

Available in all different colours, shapes and sizes, dahlias continue to be a popular choice for the summer garden, providing a rich supply of attractive, long-lasting blooms all the way through to the first frosts of the year.

Dahlias can be bought potted and in bloom in midsummer, but it is far more rewarding to select your own tubers for starting in late winter. Come June and July, all your thoughtful work will pay off in dramatic fashion as their flowerheads supply colour both for your garden, and in cut flower displays. To help with the process we have put together a guide on how to plant these grand beauties when the time is right.

In late March to early April, dahlia tubers can be started in individual pots under glass or in a greenhouse. Fill with multi-purpose potting compost and position the tuber close to surface level with the central stem facing upwards. Cover with more compost and then water well after potting, keeping the soil moist but not waterlogged.

After around three to four weeks new shoots should start to form. When two sets of leaves appear, pinch out the tips of the main shoot to stimulate the plant to produce more stems and leaves, resulting in bushier growth and more flowers!

Once the last of the frosts have passed in mid to late May your dahlias can be transferred into the garden. Dig a planting hole large enough to accommodate for your pot's size in a sunny yet sheltered position.

Keeping the soil level the same, add organic matter to increase soil fertility. If your soil is heavy clay, also add some horticultural grit to the base. Place the dahlia in the hole with the tubers just below the soil surface, fill in around the rootball and add a plant label to remind you of the variety.

It is a good idea to insert a stake when planting to provide your dahlias with support, unless they are dwarf varieties. As they grow, pinch out the tips once three pairs of leaves have grown to encourage branching. Tie in any new growth every couple of weeks.