Dahlia is one of the most beautiful flowers in the garden. But in order for the tuberous plant to please the eye for a long time, year after year, care after the end of flowering plays a crucial role. How to overwinter the dahlias, so that they get through the winter well – we tell you in the article.
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The dahlias in the garden: dig up the tubers and overwinter them in the cellar
Dahlias delight the eye with their large flowers in late summer and autumn. However, at the latest before the first frost, you should overwinter the flowers. This is because the tubers are not hardy and cannot remain outside in the bed. Even if you mulch them, the tubers will freeze. To prevent this, dig up the tubers in October.
Loosen soil and dirt, check the tubers for pests and diseases. Discard any tubers that are rotting or diseased. For the rest, shorten the stems of the flowers to 6 cm. Let the healthy specimens dry for a day in a dry and cool place. Then line wooden boxes with newspaper. Wrap the tubers with newspaper and fill the gaps with damp sand. Place the box in a dark and cool place. The garden shed, garage or basement works well.
Winter dahlias without digging them up: Is it possible?
If you want to save yourself the trouble, then you can overwinter the dahlias in a pot. However, this does not mean that the potted plants can spend the winter outside. They are not frost hardy and don’t stand a chance outdoors. Check all potted plants for signs of infestation, rot and pests. Then cut the shoots back to 6 inches. Winter the dahlias in a cool, dry and dark place. This means that you should allow the soil to dry out a bit before moving the flowers into winter quarters.
Next year, you can then either replant the flowers in the garden or plant them in containers. Dahlias require larger containers, and the volume of soil depends on the maximum growing height of each variety. For flowers that grow 1 meter high, you need a container with soil volume 35 liters. If you keep them in a tub, you can use ordinary potting soil. The dahlia has no special requirements to the substrate.
Propagating dahlias directly after wintering
Immediately after you put the tubers in the winter quarters is the right time for propagation. Place the pots with the tubers in an off-sun place in a bright room. Wait until the flowers sprout. Then cut off the shoots, remove the lower leaves and put the shoots, cut side down, in a growing pot with soil. Cover the pots with translucent plastic wrap. Regularly aerate the shoots and water the substrate when it dries out.
When the tubers are large enough, you can also propagate them by division.
Plant out the flower again in the spring
It may happen that the flowers sprout in the winter quarters. This usually happens when the room temperature rises above 18 degrees. These shoots do not harm the flower, and then simply cut back in April. If you want to extend the flowering period, you can put the tubers in a pot with growing soil already in early April. Before planting, however, you need to put the tubers overnight in a container with water so that they can soak. Then they are placed in a sunny room. It is best to find an off-sun place in the room and water the flowers only when necessary. Important condition for early sprouting: the temperature should be between 10 and 14 degrees Celsius. So the dahlias do not like it too warm. This also explains why the flowers are then allowed outdoors as early as the end of April. The pre-sprouted plants are simply strong enough and can easily survive a few nights of frost in May. By then, they have already formed their foliage, which is also advantageous in case of pest infestation, for example, by slugs or aphids. Tubers that are not pre-sprouted and do not form leaves until they are in the garden are more sensitive to leaf loss.