When is the planting season of dahlias?

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Ball Dahlia - Dahlia hortensis

The tubers of dahlias must be dug out before the winter and overwintered frost-free. From spring, they are then planted out in the garden again to unfold their true beauty. However, as the summer flowering plants do not tolerate icy temperatures, you have to wait until the winter is actually over. Only in permanently frost-free soil dahlias can easily drive out and develop at a rapid pace during spring to stately plants.


Ideal conditions for dahlias offers a sunny location. The soil should be sandy and slightly acidic. Loamy soil is not recommended for dahlias, as there is a risk of waterlogging here.

Ideal planting time

If you want to plant dahlias, you should first decide whether they are tubers, seedlings or cuttings. Tubers are usually planted directly in the garden bed. Alternatively, it is also possible to put them in a bucket or a cold frame. In all cases, the planting time is different. After planting, dahlias should not be watered unless the soil is very dry or very late in planting.
1. Plant tubers in the field
After resting in winter, dahlias can be planted in the bed from late April to early May. It is important that the correct planting depth is maintained and the soil is reasonably dry (do not plant in the wet soil). If the likelihood of severe frost is low, dahlias can land in the bed a little earlier. But once again quite apart from the spring frosts also speaks another reason against early dahlia planting out: In cold soil (especially in wet conditions) the sprouting retards, so tuberous and preformed eyes suffer. Later planted dahlias have a better start and grow faster.
In general, the frosts that occur from the end of April are only short-term and superficial. Therefore, the tubers, which are five inches deep in the ground, need not be additionally protected. If you want to be on the safe side, you can place an inverted flower pot over the planting spot and secure it with a few leaves all around. If the dahlias go wild, the pot must be removed as quickly as possible.
Tip: It is better to plant very small tubers of dahlia in pots first and then let them stir in the greenhouse (or a cool, bright room in the house). Then set in the field from mid-May.
2. Plant cuttings in the field
Cuttings may be planted in the field only after the Eisheiligen when virtually no risk of frost threatens. Since the cuttings initially have no tubers, but only fine roots, they would not survive the freezing temperatures.
3. Planting in the cold frame or greenhouse
A greenhouse protects the freshly used dahlias to a certain extent from cool temperatures. Insofar as the outside temperatures from the middle to the end of March only move around the freezing point to a few degrees below zero, they can be planted in a pot in a cold frame into the ground, provided they are later intended for planting in another bed. The transplanting of dahlias, which have already spread their roots in the ground, is difficult because they are often damaged when they are pulled out. If the dahlias in the cold frame spend the whole summer, they can be planted directly in the soil.
Tip: Soil fatigue hardly occurs in dahlias. Therefore, they can be planted over and over again on the same beds for years to come - appropriate tillage and sufficient fertilizer provided.
4. Advance
In order to give the dahlias a good lead, they plant many gardeners early in the year in flower pots and set them up to the icy saints bright and cool but frost-free (garage window, basement window, hallway or greenhouse). In this case, the tubers can already be planted in the flowerpots or pots from the end of February to mid-March. It is very important that the dahlias are bright.

planting depth

Dahlia - Dahlia hortensis

Larger dahlia tubers are inserted about a spade deep into the earth, so that they are covered with only a few centimeters of soil. Too deeply implanted, their shoots must laboriously torment themselves to the light. If the layer of soil is too thin covering the tuber, it will not grow well and is not protected against light late frosts. As a rule, cover with about a hand's breadth of loose soil.

planting distance

When the dahlias are planted at their final location, it is important to maintain the correct planting distance so that the plants can develop well and do not dispute each other's light and soil.
  • very high varieties: 70 to 100 cm
  • medium-high varieties (pompom, Halskrausen- and ball dahlias): 60 to 70 cm
  • low varieties (mignon, bed dahlias): 30 to 50 cm

Put tubers in water before planting?

Opinions differ on this question. The fact is that the tubers are often very dry after the overwintering phase. To grow better, many gardeners recommend that tubers be placed in room-warm water for a few hours or even days. Nothing contradicts this philosophy insofar as the weather at the end of April is quite poor in rain and warm. However, inasmuch as the garden floor is very humid - which is often the case in April - this procedure is not recommended. In the cold April earth, there is a very high risk of decay for the tuber.

Share tubers

If the dahlias are older and the tubers are relatively large, they should be shared. Strong gardeners can break them apart by hand, it is easier with a knife. The interfaces do not need special treatment. However, it makes sense to allow them to dry slightly before they get into the moist soil. A division is necessary because too many tuber parts hinder each other when new, young tubers are formed. The shoots are then often weak and small. The tubers should be split before planting, otherwise they will dry out during the long wintering period. At each root neck, at least one eye must be seen in the division.
Tip: If in doubt, the dahlia tubers can easily be put into the light and heat for a few days. Then they start to drift slowly.
While cuttings and preferred plants may only be planted in the flower bed after mid-May, well-formed tubers can grow in the garden soil between the end of April and the beginning of May. In order to give the dahlias a head start, it is possible to have them pushed into the house or the greenhouse from the end of February. A planting of dahlias in the cold frame is recommended from the end of March, as long as there are no permanent frosts in the double-digit minus range.

Video Board: Dahlia plants life cycle.

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