How to start off dahlia tubers in pots
March – April is the perfect time to get dahlia tubers into pots.
Whether you have tubers that you have taken out of the ground and overwintered from last year, or tubers that you have bought from a nursery, dahlias tend to grow best when started off in pots undercover, before being planted out in the ground in May, once all chance of frosts has passed.
Dahlias are one of our favourite flowers to grow each year, but there is no denying they take a bit of extra care to get them blooming happily.
One of the best ways to get a really good display of flowers from your plants, is to start the tubers growing undercover in Spring time, before the plants are ready to go into the garden. Dahlias are tender plants, so they can be damaged or killed by late frosts, so it’s best not to plant them out until late May, once all risk of frosts has passed.
However, to get them going with a head start, you can plant the tubers in pots in early Spring, and grow them under some sort of protection for a few months first. This gives the plant a a bit of extra time to put out healthy shoots before being planted out in the garden.
Planting tubers in pots is really straightforward. Here’s a step-by-step overview…
Dahlias can need a little bit more care and attention than some plants, but we think it is worth it for the profusion of glorious flowers come late Summer…
First, fill a 2l or 3l pot with compost for each tuber that you’re growing. Fill the pot half full with a good quality peat-free compost, and gently tap the bottom of the pot against a surface to help the compost settle.
Each plant tuber is a collection of brown bulb-like growths, attached to a central stem. Planting the whole cluster together will grow a big, mature plant. Put the whole cluster into the pot as one if you’re planning to grow one plant (as in the photos above).
This can also be a good time to propagate dahlias and create more, smaller plants. To do this, separate each of the individual tubers, making sure that each one has an eye, and plant them individually in pots. This will make smaller plants, which will take a few years to reach the same size, but this is a good way to multiply plants.
Check over the tuber to make sure that is healthy and free from rot.
Place the tuber on the top of the compost with the stem pointing upwards. Fill over the top with more compost. Label the pot with the dahlia name and water lightly.
Keep the pot under cover somewhere warm and frost free. Greenhouses, conservatories or cold frames are all perfect. Don’t water the pots again until the first shoots start to appear.
Fresh shoots should start to emerge in around 2-3 weeks.
This can be another opportunity to propagate plants as well, by taking cuttings. When the first shoots emerge, cut them back really low, close to the tuber, and put them in compost. They will root easily and create fresh plants, which, again, will be smaller than the parent, but will grow bigger with time… (See our guide to taking cuttings for more general info about propagating with cuttings.)
Continue growing the plants in pots until late May, when all risk of the last frost has passed. Harden off plants, before planting out in the garden. Water in well and protect from slugs and snails, which are very fond of a young plant’s growing shoots…
For more info on growing dahlias, as well as some of our favourite varieties, take a look at our dahlia plant guide.
