Planting dahlia tubers in the garden
July 14, 2015
New shoots from the seeds planted in winter will be ready for autumn sowing
The tubers produced from dahlias are so well known and have been in use for so long that they have lost their excitement for many gardeners. They are grown from seed, which in turn is expensive and the crops are liable to spot diseases in a time when plants are in need of protection. But this fall I will be putting some of these tubers in the ground with the aim of re-energising my garden and rekindling the lost romance of dahlias, which will hopefully stay with them when they come up in the spring.
In winter I planted 75 tubers, or clones, of the commercial release Aztec (meaning to me, mysterious and exotic), which was developed and patented in 1986, grown on the original company's test plots in Maine, US. It produces a round, ball-shaped tuber that grows 6-8cm diameter, which becomes a biennial plant with 3 or 4 flowers. Some of the tubers were gifts from various friends and their plantings will be familiar with me. Several of them were particularly precious gifts, some came from a visit to South Africa. They were so dark they were near black and I thought they were some kind of indigenous species I'd never seen before. The tubers have changed, from what they were when I started, into striking dark golds, some with a red blush, some with yellow, some a mixture of colours, in many different shapes and sizes.
Rows of dahlia tubers in a polytunnel
(Photo: Tammie W)
Dahlia plants get along very well in hot dry climates, but I cannot get on with them in our humid but sheltered garden, they need to be shaded and given the need for protection from drying winds. They are not a good match for a dry garden with high winds, as their robustness makes them susceptible to salt and sand, which get into their tuber development and they look strange. For years I was pondering how they could be increased by cuttings and later realised their commercial growers don't harvest them, they cut them out of their main flowering plants and collect the tubers, which can be stored for winter. I don't recommend this process, because the tubers are more vulnerable and of course if they aren't eaten they go to waste. They have gone stale and fall apart.
The tubers that grew from the seed planted in winter in my garden have started to fill out and, through careful trimming, the flower spikes have lost their spiky appearance, giving them a rounder and less intimidating look. I'll have to clean up the seed heads on the stems as they are too attractive to visitors at this time of year. But in a time of the year when flowers are, indeed, in a minority, this is exactly when I want them to be in abundance. If you take cuttings at the same time you can share the shock of their arrival in spring, and it looks like they will last a long time.
I have harvested the tubers, which were a combination of a gold, a gold with red blush, a mix of gold and a red, and a deep red. I am going to put these into some polytunnels for the winter and let the tubers, which are the big dahlia, cure into starchy storage for Christmas when you would otherwise be decorating to trees and hanging tinsel. As you know, our garden stays in seed this time of year and if you want to collect more tubers for next year you'll need to plan in early spring for next year's seed sowing.
Take the seeds of the winter-sown dahlias that are now putting up flower stalks into an airtight container to keep them fresh until spring. That way, by the time you've sprouted them out in the greenhouse or, if you're very lucky, indoors, it will be easier for them to grow to the usual size.
Also do the same for the tubers that are your main crop plants, such as: Mini Delight (you'll find this growing in your garden this year), Chieftain and Flamingo. Their tubers are also looking good and are well-behaved plants that tend not to grow too big, but rather fill in quietly to a uniform size, as long as you clip off the seed heads as they grow.
I will be going to my organic supplier again this year to see if I can get a voucher for a substantial discount on bulbs, given that spring has almost arrived, and the bulbs they give out are the sort that won't sprout until next year. I will therefore be collecting seed for as many of the other dahlia plants as possible, such as Aztec,