Whether in the garden or in a pot, asters are among the most popular garden plants in Germany. The daisy family inspires with the intense green foliage and their flowers, which appear from May to November, depending on the species, and the option of planting them directly outdoors or on the balcony or terrace. Interested parties ask themselves whether the summer aster and autumn aster are hardy and suitable for German gardens.
Summer aster: hardy?
The summer aster (bot. Callistephus chinensis) is the only taxon of the genus Callistephus and therefore does not belong to the actual aster genus. However, she is counted in the same tribe, Astereae. It is also known as the garden aster and is native to East Asia, specifically Japan, Korea and China. Compared to other asters are summer asters not hardy, as these are annual plants that, despite their robust structure, only survive for one season. The classic season of summer asters as follows:
- Sow outdoors in mid-May
- can be brought forward at home in mid-March
- Germination time: up to 4 weeks
- Flowering period: August to the end of October
- after flowering, seeds can be collected
- then the aster dies
There is nothing more to consider with the summer asters. It doesn't matter which variety of the species it is, because these are only more robust or have particularly large flowers. However, the flowering times are slightly different, so you can extend the flowering time of the plants. The above cycle also applies to specimens that are kept in pots, because the daisy family does not develop any outlasting organs and uses all its energy for flowering. However, you can delay flowering and keep the parts of the plant above ground longer:
- Location should be sheltered from the wind
- Cover the plant with fleece or jute
For example, house walls and places under roofs that protect the asters from cold winds have become established. Balconies are usually not recommended. Although these are often quite warm, they are exposed to the wind without mercy.
Callistephus chinensis, summer aster
tip: typical of Callistephus chinensis is its susceptibility to aster wilt, in which fungi block the absorption and transmission of moisture within the plant. For this reason, you should never sow summer asters in the garden in the same place to prevent possible infection, as changing the location is effective against the fungi in the soil.
Herbstaster: hardy?
With the autumn asters you can look forward to hardy asters compared to the summer asters. However, you have to be careful here, because the term autumn aster means different types of asters of the genera Aster and Symphyotrichum. These are plants that form rhizomes as an outlasting organ and thus survive the winter. They are mainly from North America and Asia. The flowering period of the plants extends into late autumn, which has earned them the nickname "autumn tasters".
autumn asters
The following species are usually meant, whose winter hardiness is given with the corresponding winter hardiness zone (WHZ or Z):
- Tawny aster (bot. Symphyotrichum novae-angliae): Z2 (-45.5 °C to -40.1 °C)
- Smooth-leaf aster (bot. Symphyotrichum novi-belgii): Z2 (-45.5 °C to -40.1 °C)
- Pillow Aster (Symphyotrichum dumosum): Z3 (-40.1 °C to -34.5 °C)
- Heather aster (bot. Symphyotrichum ericoides): Z3 (-40.1 °C to -34.5 °C)
- Asiatic wild aster (bot. Aster ageratoides): Z7 (-17.8 °C to -12.3 °C)
This is just a small overview of the variety of genera, because Symphyotrichum alone has numerous taxa that have a similar winter hardiness. Of the more than 90 species, the four mentioned are the most established as garden plants in Central Europe and can be planted without any problems. For this reason, you will most likely find these most often in stores.
Asters overwinter
In the species of the genus Aster, it is the wild aster that is suitable as an autumn plant and delights with its flowering from September to the end of October. Best of all: all autumn asters receive the same winter protection outdoors, which makes keeping them easier:
To cut
Do not cut back the asters in autumn. Although the plants are hardy, it is necessary that they have sufficient plant material to protect the root ball. The dried-up foliage and flowers are best suited for this, and can easily be cut back in the following spring. In addition, the dried plant parts ensure a picturesque look in wintry grey.
winter protection
A good winter protection for the asters is soil enriched with compost. Since asters are very hungry, the compost ensures a sufficient supply of nutrients over the winter so that the plants can sprout and be cut again immediately after the winter. Distribute the fresh compost soil thoroughly around the root balls of the asters so that they are well covered.
Last but not least, there is a layer of brushwood. Twigs make a good winter shelter, especially for the Asiatic wild asters, as they need more shelter than the Symphyotrichum asters. When distributing the brushwood, be a little generous.
If you have decided to grow asters in tubs, you must definitely provide winter protection, as it is not recommended to bring the plants indoors over the winter. However, since the pot can easily freeze through, it needs a new location:
- Light requirement: bright
- southern orientation
- The balcony and house walls are well suited
- sheltered from the wind
If you live in a region where it rains a lot, you should also place the potted plants in a location that is protected from precipitation. But that means that you have to water yourself over the winter.