The Expert Guide To Growing Dahlias

If you are looking for high drama and a blaze of colour for your garden, patio or window boxes then dahlias tick all the boxes.  Rosebie Morton, founder of The Real Flower Company, shares her top tips on how to grow them.

Rosebie Morton’s April Gardening Guide 2026

Flowering from mid-summer to early winter, few other flowers can rival dahlias for sheer flower power. They come in a huge range of colours, from the palest muted tones to bright electric pinks and purples, and in many different shapes, including pompom, ball, cactus, waterlily, anemone or even dinnerplate. 

At this time of the year, they are available to buy from any garden centre or online site. Don’t be put off by the brown mass of roots (known as tubers) with the dead stems at the top; this unprepossessing lump will quickly burst into life. If you have time and want to get ahead, soak your dahlia tuber in a bucket of tepid water for a couple of hours (especially important if the tubers look shrivelled). This will allow the tuber to rehydrate and then it can be planted into a pot containing well drained, peat free, multipurpose compost. Plant it a couple of inches below the surface and water it without soaking before placing it in a sunny frost-free space –⁠ a windowsill or cool greenhouse is ideal.

You should start to see shoots appearing in a few weeks but keep the pot protected until there is no more risk of frosts before moving the dahlias out to the garden. If you are leaving them in containers then just keep them watered and only start to feed them once they are settled with several sets of leaves, doing so every two weeks with a high potash feed (tomato feed is ideal) . If you are planting them in the ground, put them into well dug soil with some compost and a slow release fertiliser, and then water. Feed them the same as the containers but only every three to four weeks. 

How To Choose Your Dahlias

The question of where to grow your dahlias is often determined by the variety you choose. If you are thinking of keeping them in containers then opt for the compact dwarf or bedding varieties such as Totally Tangerine, which can flower as early as June but will continue through to November. The single-flowered Bishop of Llandoff is another popular choice (particularly with pollinators), with its eye-catching dark purply-bronze foliage and bright red flowers. Alternatively, go for for Daisy Duke dahlias which only grow to 60–90 cm tall on sturdy stems; their beautiful sunset-like coral flowers are perfect for containers. 

If you are looking for impact and height in your borders, consider what colour will work best. Cornel, for example, is a bright, attractive red-ball type dahlia, while Cornel Bronze is another ball in a lovely orange colour, both of which are renowned for their disease resistance. For pinks, Sweet Nathalie is a beautiful creamy blush decorative dahlia perfect for cutting, and Great Silence is anything but with its big double blooms in a vibrant bright coral pink – a serious showstopper. Or, for real drama, go for Thomas Edison: a huge dinnerplate dahlia with deep purple flowers.

The taller the dahlia the more they will need staking, especially in a windy sight. If you can lay your hands on some hazel sticks or, failing that, some bamboo canes, these will keep your prized blooms from snapping. Other than being hungry feeders, dahlias enjoy a sunny site and regular watering. To get them to flower continuously, be diligent on deadheading and you will be rewarded by a fantastic display all summer long.