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Dahlias are among the loveliest summer flowers. Their large and sometimes heavy flower heads provide spectacular splashes of color in the garden or on the balcony and terrace with their unusual colors and color gradients. They bloom from summer until the first frost. The growth heights of the individual varieties are also different. However, what all varieties have in common is the lack of frost hardiness. It is all the more important to pay attention to the right planting time.
planting time
Best time to plant
Due to the lack of winter hardiness, you should generally wait until spring before planting. The right time depends on whether it is the tubers or young plants or advanced dahlias. Dahlia tubers can be planted in the ground from the end of April/beginning of May. Possible night frosts can usually no longer harm them at this point, since they no longer penetrate the soil. The situation is different with young plants or those that have been brought forward. They should not be planted before the ice saints, i.e. not before May 15, because the sensitive roots would not survive frost.
white dahlias
Prefer dahlia bulbs
- by bringing the dahlias forward, shorten the waiting time until flowering
- early sprouting in the winter quarters, another reason for a preculture
- too warm hibernation mostly cause for premature budding
- plant these tubers as soon as possible
- otherwise it comes to the formation of so-called Geiltriebe
- best time around February/March
- put the tubers in moist substrate to prefer
- put the whole thing in a warm place with 15 - 20 degrees
- for example on the window sill, in the cold frame or conservatory
- get young plants used to sunlight and outside temperatures after they have sprouted
- put it in a sheltered place outdoors on cloudy days
- Plant out in the garden after the ice saints, from mid-May
Specimens that are to be kept permanently in tubs and are later intended to embellish the balcony or terrace are best placed in suitable pots right away. That way you can save yourself the hassle of repotting. In the spring they can then be put outside permanently.
Tip: Plants that have been pushed forward are usually more robust and less susceptible to snail damage. In addition, this growth advantage leads to a more lush bloom.
plant spacing
These grandiose permanent bloomers need enough space, they should not be too dense. Otherwise they could hinder each other in their growth. The optimal planting distance depends on the respective dahlia variety or whether it is a high (up to 180 cm), medium-high (up to 120 cm) or low-growing (30 - 50 cm) variety.
Dahlias in the garden bed
The taller the dahlias grow, the greater the distance between the tubers should be. In general, they should be about half to a third of the final growth height. This results in a planting distance of about 30 - 40 cm for low specimens, 60 - 70 cm for medium-high varieties and a distance of up to 100 cm for tall varieties.
planting depths
The correct planting depth depends on the type of dahlia and the size of the tuber, as well as whether the plants are tubers or young plants. Tubers should be planted so deep that they are about 3 - 5 cm covered with soil. If you set them too deep, they will sprout much worse. In the case of young or early plants, care must be taken to ensure that the crown sits directly above the surface of the earth after it has been planted.
Tip: A general rule of thumb for determining the depth of tubers to be planted is that they should be covered with soil to two to three times their size.
Instructions for planting
In the garden
For planting choose a sunny, sheltered spot with normal, deep and well-drained soil. Waterlogged soils are unsuitable. Heavy soils are loosened up beforehand with coarse-grained sand. Slightly sandy soil can be improved by adding compost. Sandy, slightly acidic soils with a pH of 6.5 are ideal.
- Take tubers out of winter quarters in spring
- Remove old remains of soil and sort out rotten tubers
- Large specimens are best divided with a sharp knife
- if not, leaves and fewer flowers are formed
- each section should have buds or shoots
- Then allow the interfaces to air dry for 2 - 3 days
- this is to avoid rotting
- Tubers usually lose a lot of water during the winter
- however, avoid watering if possible
- there would then be a risk of rotting in the still cold, damp soil
- Dig a spade-deep hole for each tuber for planting
- Put a handful of horn shavings, some compost or cattle manure in the planting hole
- Use dahlias, taking into account the planting distance and planting depth
- Cover tubers with soil and press them down lightly
- Water the first time when you can see the shoots
With medium-sized and large dahlia varieties, it is advisable to use appropriate support rods when planting and to tie the dahlias loosely to them with enough play. This is to prevent them from buckling during flowering due to their size and relatively heavy flower heads in windy weather. The respective supports should be hewn or beaten into the ground before inserting the tubers. In the opposite case, it could easily happen that you injure the tubers.
Dahlias with yellow flowers
Tip: If you have a problem with voles in your garden, you should plant the dahlias in the ground using a sufficiently large, close-meshed wire basket or wire mesh to protect them from damage or total loss.
In the bucket
As an alternative to the garden, dahlias can also be cultivated very well in pots or tubs. Depending on the dahlia variety, the respective planter should have a capacity of at least 7.5 liters and a diameter of 25 - 50 cm. Any well-drained and nutrient-rich potting soil is suitable as a substrate. A drainage layer of potsherds or coarse gravel is placed on top of the drainage holes and then the substrate. The tubers are placed in the middle at the appropriate planting depth and then filled with soil. Suitable supports should also be used when planting in containers.