When I started gardening ‘dahlia’ was almost a dirty word among gardeners – except for keen gardeners who would cherish dahlias for cut flowers and the exhibition table at their local flower show. But as plants for garden design or display, dahlias were unacceptable. Of course, annual dahlias, grown from seed, for bedding in rows along with salvias and lobelia, had their advocates but among the fashionable, they were just as unmentionable.
But things changed slowly, largely, I believe, to the ‘rediscovery’ of a single cultivar. When ‘The Bishop of Llandaff’ was thrown into the spotlight everyone looked at dahlias differently. Here was a dahlia with single flowers, not at all like the exhibition kinds. And it had rather fine, deep beetroot foliage that added as much to the border as the dazzling blooms. Christopher Lloyd was encouraging us all to eschew the pastel colours of the previous decade and ‘go jungly’ as he dug up his rose garden and replaced the prickly bushes with cannas, bananas and the most exuberant dahlias. Times were changing and dahlias were suddenly the height of fashion.
Lots more ‘Bishops’ appeared and there is even a strain of seed called ‘Bishops Children’ which always makes me wince a bit. Plant breeders got to work to produce lots of dark leaved dahlias in various heights and flower colours. These single-flowered dahlias are easy to grow from seed. This year I grew ‘Black Forest Ruby’ an ‘award-winning’ seed strain. Seeds were sown in late March and plants have been in bloom for a few weeks. The flowers are supposed to be single to double but all mine are single and although they are vibrant, I am not blown away by them so far. If they keep blooming all summer and tolerate the extreme heat then I will change my opinion. Of course, if you grow dahlias from seed you can save the best plants for next year by digging up and storing the tubers.
If you want dahlias for cutting you probably want the double-flowered kinds and these are best bought as tubers. The breeder will have raised thousands of seedling and selected the finest for you.
You probably started your dahlias from tubers in spring. Now they are growing strongly, and the weather is warm and sunny there are a few things you can do to get the best from them.
Firstly it is important to remove the faded flowers, ideally with the stems down to the next leaf. This prevents seeds forming and encourages more flowers. Later in the season, when the weather is cooler and wetter, it will prevent petals dropping onto the lower parts of the plant and will help to prevent mould and rot. Single flowers tend to last less time than the big doubles but they are better for pollinators so are increasingly popular.
Most importantly, you need to make sure your plants are well watered. Dahlias love the sun and they will withstand a certain amount of drought, but they will only bloom to their full potential if they are kept evenly moist. They also must be fed and you can apply a fertiliser such as fish, blood and bone or chicken pellets now to maintain growth – but these are only effective if watered-in.
Plants in containers must never be allowed to dry out and you should feed them every week too with a liquid fertiliser such as tomato fertiliser.
If you want the largest flowers and the best stems for cutting you should ‘disbud’ them.
As soon as you see the main, top bud has formed on each stem, pinch or rub out the side buds and the two side shoots lower down on the stem. This means you get fewer flowers but the best, perfect flowers on long stems,
It is also worth mulching your plants with compost or whatever you can get hold of, to help maintain soil moisture and to keep the roots cool and moist.
With care your dahlias will keep on blooming until the first frost of autumn, which should be months away yet. Few garden plants can promise that!
You can buy dahlias growing in pots already in bloom and they are a perfect way to add instant colour to your borders – just keep them watered!
Weekly reminders
There is just about time to sow some salads for autumn crops as well as the last sowings of carrots and French beans. It is also time to sow Oriental veg, fennel and endives and chicory.
Raise the height of the mower in this hot dry weather but continue to mow to keep coarse grasses under control
Make watering you patio pots and hanging baskets a priority.