These reliable varieties will fill vases with brilliant blooms this summer
Dahlias are the ultimate ‘cut-and-come-again’ flower. They come in sumptuous colours, from softest peach to darkest red. Flower shape varies too, from quilled cactus to soft waterlily to pure single and on to tight pompom, to name but a few. They will all provide flower power from July until the first frosts and these days that can mean four or more months of blooms. Best of all, many of them cut beautifully and growing your own cut flowers is bang on trend. Everyone’s doing it!
Beware of frost
These frost-tender, tuberous plants began life in the high plains of Mexico, where days and nights are evenly balanced. As a result, they only get into their stride once the nights begin to draw in. Their frost-tender foliage shouldn’t go outside until the first week of June, because it could suffer frost damage or cold shock. If you’ve got or have just bought dahlias in pots now, they’ll be perfect for planting out in early June. If they’re getting leggy, pinch out the tips to bush them up.
Once planted out, your dahlias will romp away and they don’t need nitrogen-rich plant foods because this will promote growth rather than flowers. You can water on a high-phosphate tomato food once the buds appear.
Shall I leave them in?
There’s always a debate about whether to leave dahlia tubers in the ground over winter. Most gardeners prefer to lift them for several reasons. You can lose your tubers in severe winters – I did in 2012 – and they can’t always be replaced like for like. They emerge late so there’s a maddening gap until early May. In fact, they don’t have much of a presence before July. Large tuber masses also tend to be shy on flowers after three or so years. Some gardeners hedge their bets and leave some and lift some.
The Great Dixter System
If you want to grow dahlias in your borders you’ll need to create gaps for them, because they don’t like close competition. They find it very hard to push up through herbaceous plants. The gardeners at Great Dixter in East Sussex have a perfect system. They plant spring bedding, such as tulips, wallflowers and myosotis, in autumn in a gap in the border. The bedding is lifted in May and the dahlias replace it in June, when they’re well-rooted.
A dedicated cutting garden
If you’re growing them for cutting, a dedicated dahlia bed works well because you can space them out and get to them easily. Infilling with taller, later-flowering annuals, such as cosmos and monarda ‘Lambada’, adds more colour and the stems of these annuals offer some support too that saves staking. Verbena bonariensis, the stalwart purple-flowered perennial, has rigid s
