Potting and advancing dahlias

How to start your dahlias early:

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Give your garden a unique look with our special dahlias. Not sure where to start or how to pot them up? We are happy to explain. Dahlias cannot tolerate frost, which means they should only be planted outdoors after the last frost has passed. In most areas, this is around mid-May.

To give your tubers a head start, you can begin growing them indoors in March or April. This is called pre-sprouting or potting up. You plant the tubers in a pot, and by the time you move them outdoors after mid-May, the roots will have developed and the first shoots will already be visible. This means your dahlias will bloom a few weeks earlier. An added bonus: the young plants are better protected from slugs, who love those tender new shoots.

Step-by-step: how to start or pot up dahlias indoors

1. Use a large plastic pot about 20 to 30 centimetres wide with drainage holes at the bottom. It’s best not to use a terracotta pot, as the soil dries out too quickly. Fill the pot with potting soil, leaving about 10 centimetres of space from the rim.
2.   Depending on the size of your pot, place one or more dahlia tubers on top of the soil with the old stem facing up. Then fill the pot to the top with more soil, press it down gently and give it a small splash of water. Keep the soil slightly moist but never too wet, as this can cause the tubers to rot.
3. Place the pot in a bright, frost-free spot indoors — for example on a windowsill, in the attic, in a small greenhouse, shed or cold frame. Dahlias grow best in a light spot at a temperature between 15 and 20 degrees Celsius.
4. If the shoots grow too long, move the pot to a brighter or cooler location. When the plant reaches 30 to 50 centimetres in height, pinch out the central shoot just above the third pair of leaves. This encourages the plant to branch out into a bushier shape with more flowers. You can also do this later once the plant is growing in the garden.
5. By the time the risk of night frost is over, usually around mid-May, you can plant the dahlias outside. Choose a sunny spot. If there is still a chance of frost, protect the young shoots. Dig a generous hole, gently remove the plant from the pot and plant it at the same depth in the ground. Cover with a few centimetres of soil.
6. Then let summer begin and you’ll see your dahlias already starting to bloom by midseason. They will continue flowering right up to the first frost!

PS: Some tubers sprout faster than others. Sometimes it takes up to five weeks, so don’t worry. Just give them a little love and patience.