An early start for Dahlias

1st February 2024

Flowering non-stop until the frosts, dahlias are probably one of the best value plants. Nothing else will give you the same flower power for the few quid the tubers cost, or space they need to grow. They are hugely valuable as flowers for cutting, given their unrivalled productivity and good vase life. The vast range of colours, forms, foliage and size available, is almost unrivalled by any other plant group. There are over 57,000 cultivars of dahlia now registered, and gardeners are embracing their versatility. Some cultivars are specifically bred to do well in pots, while others have been selected not just for the beauty, but their attractiveness to pollinating insects.  

Dahlias have seen a renaissance over the past decade. They fell out of favour, as people saw them as fussy, overly blowsy and formal, and old fashioned. But people are embracing them once again, as perennial plants that just keep giving.

The lowest fuss way to grow dahlias is simply to plant the dormant tubers directly into open ground or pots outdoors in late May, once the risk  of frost has gone. They’ll soon send up shoots get growing with the summer warmth, and hopefully you’ll have flowers by August. In colder areas, or with more fussy slower growing larger flowered varieties, you’ll probably find the flowers only really get going by late September. Slugs love dahlias, so getting them started outside can be a high risk strategy. If the slugs nibble the emerging shoots as they grow, there’s a chance the dahlia will fizzle away. One thing that is true of dahlias in general, is the high variability in the time it takes for tubers to break dormancy. Even tubers from the same variety can be variable. Some will show shoots within a week, whereas others may erupt 6 or even 8 weeks later. 


But now in this month of February, you can avoid some of these pitfalls by starting dahlias indoors. Getting them started now is a good idea in lots of ways. Firstly, getting them off to an early start means they’ll be flowering from as early as June, all the way until the frosts, probably in November. That's 6 months of flowering. Secondly, when you plant them out in late May or early June, they’ll be good sized plants growing vigorously, and able to take a little slug damage in their stride. Lastly, you have plenty of time to make things right if they go wrong; some tubers fail to ever break dormancy, or they just take a really long time.


They’ll need somewhere warm and bright. This could be a frost-free glasshouse, or more commonly, a sunny windowsill. Either pot each tuber up individually, or if you’re a bit pushed for space, lay all the tubers in a shallow tray and give them a thin covering of compost. Keep them just damp but not soaking. In a few months time they can be pulled apart, and potted up or planted out. 


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