When autumn comes in the garden, the chrysanthemum, one of the most popular bedding and balcony plants, makes its grand entrance. The variety of species offered in the trade is almost inexhaustible. There are filled and unfilled varieties with single or multicolored flowers and different flower shapes. In addition, a distinction is made between annual and perennial species. Their winter hardiness is significantly influenced by the time of planting and the site conditions.
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Planting time determines type of overwintering
Chrysanthemums are basically perennial, hardy plants. Thanks to numerous breeds and crossings, many varieties are now available that are not hardy and are usually only cultivated as an annual. Hardy specimens can be recognized by the fact that they are offered as garden or autumn chrysanthemums, also known as winter asters. But that doesn't mean that you can't overwinter supposedly annual varieties and bring them to bloom again next year.
Whether a chrysanthemum can overwinter in the bed or has to spend the cold season in a frost-free area depends initially on when it is planted. If you want to overwinter the plants in the bed, you should decide to plant them in spring. Only a correspondingly early planting ensures that the plants have enough time before the onset of winter to develop a strong and deep root system in order to survive the frosty temperatures. A light winter protection is still recommended.
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Buying and planting in autumn is therefore not recommended. These plants cannot build up sufficient winter hardiness in the short time and would not survive the first winter in the ridges. Nevertheless, you can also save them over the winter by overwintering them in a pot frost-free for the first year.
Tip: In order to create the best possible conditions for overwintering, you should avoid buying plants that have been grown in pots in a greenhouse if possible. Instead, one should prefer specimens from nurseries. They usually grew up in the fields and have already gotten used to the harsh climate.
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Soil conditions optimize winter hardiness
Another factor that can affect the hardiness of chrysanthemums is the soil condition. The biggest enemy of hardy chrysanthemums is permanent or standing water. Therefore, soils that tend to waterlogging should be avoided or prepared accordingly.
- to mix in coarse portions in soils with a high clay content
- about one third sand, fine-grained grit or gravel
- coarse parts make the soil more permeable and at the same time thin it out
- Planting in the rock garden or gravel bed offers protection against waterlogging
- if necessary, a hillside location is an advantage
For potted plants, it is advisable to use high-quality potting soil, which can also be improved with perlite, fine-grained gravel or quartz sand.
Tip: The administration of a potassium-rich fertilizer in early autumn can also have a positive effect on the winter hardiness of the plants.
In the bed
Hibernation in the bed
The hardy garden chrysanthemums are usually hardy and can easily overwinter in the bed. That doesn't mean they can do without any protection at all, especially during particularly cold and wet winters. With an appropriate cover you can protect against it.
For example, you can cover them with several layers of fir brushwood before winter. Leaves, especially damp leaves, should not be used as cover. Firstly, chrysanthemums do not tolerate excessive moisture, and secondly, they could easily rot under it. You should also avoid pruning the flower stalks before winter, because they offer the plants additional protection against the cold.
In the pot
Overwinter hardy chrysanthemums in pots
In mild locations and with appropriate protection, hardy chrysanthemums can also overwinter in pots outside. In order to offer them the best possible protection, they should preferably be placed against a warm house wall, if possible on an insulating styrofoam plate or wooden pallet.
- then wrap the bucket with garden fleece, bubble wrap or coconut mats
- additionally cover the root area with plenty of fir brushwood
- for pots with a diameter of less than 30 cm, protective measures are not sufficient
- in small pots the soil would freeze relatively quickly
- these plants should overwinter frost-free
If you want to be on the safe side, you can overwinter hardy chrysanthemums in a pot by burying them and the pot in a sheltered place in the garden and also covering them with brushwood. In the spring, when the severe frosts pass, the shelter can be removed. It is watered only sporadically and only on frost-free days. The ground should not be frozen.
Tip: If overwintering still fails, it is advisable to cut cuttings before winter and grow new plants from them. This is particularly useful when it comes to particularly beautiful or rare varieties.
winter quarters
Frost-sensitive varieties overwinter
Frost-sensitive chrysanthemums are usually offered as pot chrysanthemums in autumn. But they can also be overwintered under certain circumstances. In contrast to hardy specimens that hibernate outside, non-hardy ones are cut back to a height of about 10 cm before moving to the winter quarters.
Before the first frosts, the plants are then put into the house. The winter quarters should be light and cool with temperatures between 3 and 10 degrees. This can be an unheated conservatory, a cold house, attic, cellar or a cool stairwell. It shouldn't be warmer than 12 degrees. The warmer the winter quarters, the more often the plants have to be watered. The substrate should not dry out completely if possible. Don't fertilize during the winter.
To cut
Cut back before and after wintering
Chrysanthemums that overwinter indoors should be cut back to a height of about 10-12 cm before winter. The situation is different for the specimens that overwinter outside. A pruning in late autumn is not advisable here. Both the foliage and the stems serve the chrysanthemums as additional winter protection in addition to the typical cover.
Only in spring, around March, when the new shoots appear, can a corresponding pruning be carried out. The withered stalks are cut off close to the ground without damaging the new shoots. Later, when the plants are about 50 cm high, they are cut back in half again to achieve better branching and stability.