Dahlias and other tuberous plants are a symbol of a splendor of flowers in the summer garden. Preparations for cultivation can begin as early as the end of February. However, if the dahlia tubers awaken in March, planting them outdoors is not an option as they are very sensitive to cold and moisture. Therefore, it is advisable to prefer dahlias. This gives the magnificent, permanently flowering plant a good head start over specimens planted directly outdoors.
Advantages
After planting outdoors, it usually takes around 4 to 6 weeks until the first shoots appear on the tuber. If the dahlias are placed in a warmer room or greenhouse to grow them, they will sprout more quickly.
- Time until sprouting: a few days (instead of weeks)
- less total failure due to snails and other animals
- Blooming from June
When to bring forward
If the dahlias have spent the cold season in their frost-free winter quarters, the tubers awaken from their hibernation as temperatures rise. The first shoot tips often appear in the winter quarters, especially if the tubers are stored too warm and dark. If the dahlias are not planted promptly, further storage will cause the shoots (light shoots) to turn yellow. There is also a risk of fungal infections occurring when the humidity is high. However, at the end of February or beginning of March it is still too early to plant the tubers outdoors. They would not survive the cold and wet soil conditions. These dahlias must be grown in pots or in a frost-free greenhouse.
Preferring as an option
For gardeners who don't want to wait until the ground is frost-free so that the dahlias can be planted directly in the bed, there is the option of planting them in flower pots.
- Time: from the end of February in flower pots
- in the cold frame from March (covered with glass)
- Temperature: optimal temperatures are around 15 degrees
- Minimum temperature: about 5 degrees
Growing dahlias in pots
If the flower pots are only used for pre-culture (not pot culture), the size of the pot is simply adjusted to the size of the tuber. Since the dahlias will be planted outdoors from mid-May anyway, no additional space for the roots needs to be taken into account. The planting depth in the pot of around five centimeters below ground level (top edge of the tuber) should always be maintained. Dahlias that are planted too shallow will not stand firmly enough in the soil later.
- first fill in gravel or expanded clay as drainage
- smaller tubers can also grow in old flower boxes
- Fill about two-thirds loosely with soil
- Place tubers on the ground
- divide large tubers (at least one eye per section)
- make sure that the shoot tips are at the top
- cover with three to five centimeters of soil
- Don't press the earth
- Fit the pot firmly a few times (to avoid cavities)
- label with plant label
- For tall varieties, a plant stick can be used at the same time
- do not water
Tip:
Regular ventilation (putting them outdoors when the weather is nice) is essential to prevent diseases and pest infestation if the dahlias are grown indoors.
pot planting
If you would like to plant your dahlias on the terrace or balcony, it is best to plant the tubers straight away in the appropriate pot size. The diameter of the container should be about half the height of the plant. This ensures that the fully grown plant has enough space and is secure.
Substrate
Dahlias do not have high demands on the substrate for growing. However, it should be well permeable to water. It is important that the soil is not completely dried out, which is unfortunately often the case with leftovers from the previous year. In this case, the substrate should be slightly moistened before planting. Extremely dry soil absorbs moisture very poorly; it is either washed away in the pot or the water simply runs through it. To moisten, fill the dry substrate into a bucket or large bowl, add a little water and mix the soil well. It is best to cover it afterwards and wait one to two days before planting the dahlias. In the meantime, you should mix a few more times and maybe add a little water.
- Substrate: potting soil
- alternative: mixture of potting soil and sand
Pouring
In principle, dahlias need a lot of water. However, if the dahlia tubers are freshly planted, they should not be watered at first. The tubers have not yet developed roots with which they could absorb water. Therefore, dahlia tubers rot or mold very quickly in moist soil. Fears that the dahlia will not sprout if left unwatered are unfounded. A sufficient supply of water is initially guaranteed from the tuber itself. When the first shoots appear, watering can begin very carefully. However, the earth must never be wet.
Tip:
Many gardeners swear by soaking the tubers in water for a few hours or days before planting. This is not necessary, but can be done. Under no circumstances should additional watering be carried out!
Location during advance
The place where the dahlia tubers sprout should preferably be slightly below room temperature. It is important that the dahlias are very bright. When the first shoot tips appear, the pots can be placed in the sun on a protected house wall for a few hours, even when the weather is nice. If it gets windy or cold (especially at night), the dahlias definitely have to go back inside.
- Temperature: 8-20 degrees
- Window sill (light)
- bright staircase
- Winter Garden
- Greenhouse
Tip:
The cooler the dahlias grow, the longer they take to sprout. However, places that are too warm are dangerous because the supply of water (through the roots) is not yet working. A good average is around 15-18 degrees.
Prefer dahlias in cold frames
A cold frame under glass, like a greenhouse, protects against frost to a certain extent. On clear days, the cold frame heats up through the glass pane, thus ensuring optimal conditions for sprouting. Anyone who plants tuber plants such as dahlias in a greenhouse or cold frame must consider whether they should remain there all summer or just for pre-growing. The tubers should only be planted in the ground if that is their final location.
- First plant tubers in flower pots
- Place pots flush in the soil
- water carefully only after sprouting
- as soon as there is no longer a threat of frost, plant in the final location
Tip:
Planting the tuber in flower pots makes transplanting much easier and protects against injury to the tuber or roots when transplanting. Additional side effect: voles have a hard time getting to the tubers.
Fertilize
From around mid-April it is advisable to provide the fast-growing dahlias with a few nutrients for good and he althy development. Horn shavings (long-term fertilizer) that are incorporated into the loose soil have proven successful. Guide measure: one teaspoon of horn shavings per tuber. When planted outdoors, the dahlias receive fertilizer for the second time. It has proven to be a good idea to incorporate a good portion of compost into the soil before planting.
- one teaspoon of horn shavings per tuber
- Planting outdoors: mix compost into the soil
- alternatively, work cattle dung or chicken manure into the garden soil in the fall of the previous year
Cut early
Relatively small tubers often sprout only weakly. In order to promote the formation of shoots, the main shoot (thickest shoot) should be removed early on in tubers that only form three or four shoots. If the shoot that costs the tuber the most energy is no longer there, several new shoots usually form on the tuber within a short time.
Conclusion
From the end of February, dahlias can be grown in flower pots in a bright and warm place. This is absolutely necessary if the dahlias have already sprouted in their winter quarters but it is still too cold outside to plant them outdoors. Allowing the dahlias to sprout can also help give the plants a good head start. In a warm place they grow faster and there is less risk of pests and diseases that lurk on the plants in spring.
