September in the cutting garden and my Dahlias have been flowering since early July. Dahlias are one of the lowest maintenance, highest production cut flowers you can grow. In a good year, they can be in flower from late June to early December (especially if they are in a sheltered spot). There are a huge range of shapes, colours and sizes and you're missing out if you aren't growing them. Don't be put off if you don't like blousy, showy, pom-pom flowers, there are some lovely simple flower shapes too.
Dahlias are frost tender so tubers should only be planted outside once all risk of frost is over. I start mine off in pots in the potting shed in March-April so there's plenty of time for you to browse catalogues to find the colours and flower shapes you'd like to grow next year.
Dahlias are natives of Mexico and Central America and were first introduced into Europe by Spanish explorers. Most plants have 2 sets of chromosomes but Dahlias have 8 sets which allow them to be exploited by plant breeders to create numerous hybrids. There are over 1,600 different varieties registered with the National Dahlia Collection here in the UK.
This year I seem to have focused on growing dark red Dahlias, having grown 3 types of a very similar colour but all with differing flower shape. In my defence, one, ('Sam Hopkins') did come free with a bulb order and I think it has become my favourite Dahlia. Dark red is a colour that looks great as the light levels change in Autumn and adds a jewel-like tone to arrangements. It looks great with soft pinks and with blues. I've also grown a hot pink variety as a contrast and tried to grow a white variety 'Blanc y Verde'. This has been a lot slower-growing than the others but is just showing signs of coming into bud as I write this article.
Dahlias by flower form
Pompon, ball and miniature ball
Spherical heads made of 100s of tightly packed half-furled petals. Very large pompon heads can be difficult to use as cut flowers but there are some smaller ones which work really well in mixed arrangements or displayed simply on their own.
This type have flat, daisy-shaped flowers with 8/9 petals and these simple flower forms are best if you want to attract bees and other pollinators to the garden. They can be bruised easily and don't last that well for cutting compared to some other Dahlias but I love the simplicity of them.
The flower heads are comprised of 100s of spiky petals and even though the pollen is hidden deep inside it is still accessible to pollinators. I've grown 'Nuit d'Ete' which is a lovely dark red variety.
A more relaxed version of the cactus variety with less spiky petals.
Possibly my favourite type of Dahlia with an exquisite double flower head. One or more rings of flattish petals surround a densely packed centre made up of tubular florets that point upwards. 'Blue Bayou' is beautiful with lavender outer petals and deep purple pin cushion centres. I had a lovely one last year but the tuber went mouldy over the Winter. Definitely one I will grow again.
Vast flowers the size of dinner plates. A bit unwieldy for flower arrangements.
Waterlily shaped flowers. Many of the Karma series which are thought to be some of the best lasting of the Dahlias as cut flowers are this elegant flower shape.
Softer than the pompon/ball varieties but still with hundreds of petals. Not quite a cactus or a waterlily. Good for cutting. I've grown dark, velvety-red 'Sam Hopkins' which is stunning as is the similarly coloured 'Arabian Night'.
Earwigs can be a problem with dahlias. They love eating the flowers and leaves and I often get surprised by an earwig or two when I bring them into the house so it's a good idea to give them a bit of a shake before bringing them in. You can also try to control them by placing pots filled with straw upside down on top of canes by your Dahlias. The earwigs will crawl into the straw during the heat of the day and at the end of the day you can remove the pots and dispose of the earwigs however you wish. Slugs also love dahlias, especially when they first shoot, so you will need to protect them as soon as you pot them up.
Only pick dahlias in full flower as they will not always fully open if cut when emerging from the bud. Re-cut the hollow stem ends under water to avoid air locks. Deadhead your Dahlias regularly if you don’t pick every flower for the house. This improves how the plant looks and will prolong flowering.
For more Dahlia inspiration and to view all Dahlias mentioned, visit my Pinterest page.