Chrysanthemums are among the most beautiful autumn plants. But what happens to the flowers after the end of the flowering period? Can they overwinter outdoors or are they not frost hardy? We take a closer look at the question and explain which chrysanthemums are hardy and how you can recognize them.
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Are my chrysanthemums winter hardy?
Chrysanthemums belong to the “Asteraceae” family. These beautiful flowers are actually native to Asia and do best in regions with a mild climate such as the southern parts of China and India. They were brought to Europe 3 centuries ago. Nowadays, there are various cultivars that decorate the home garden and balcony. However, most varieties are not hardy. We take a closer look at the different varieties.
Chrysanthemum hybrids in pots are not frost hardy
In garden centers, you can find several small-growing chrysanthemum varieties. Most hybrids are specially grown as annuals and are not frost hardy. If you have purchased fully grown plants in full bloom in the fall, they are most likely the fall chrysanthemums . They are pre-pulled in garden centers in the summer and are then available starting in September. Normally, flowering is encouraged by regular removal of the wilted. With good care and a warm fall, this can extend into November. After permafrost sets in, the hybrids die. However, overwintering indoors is possible, but flowering will diminish over the next few years.
Winter asters can spend the winter outside
Unlike other autumn-flowering chrysanthemum varieties, which have a compact habit and are grown as low flowers in pots, winter asters are perennials with a spreading habit and a maximum height of one meter. Winter asters are available mainly as young plants in growing pots. You can buy them in the spring, just before planting. However, it makes much more sense to buy them in the fall – then the flowering perennials do not have to spend the winter in a warehouse.
Winter asters are considered hardy. However, the young plants are still somewhat sensitive to frost. Although they can spend the warm autumn months – September and October on the balcony or terrace. But you need to put the pots on a polystyrene base, so that the roots do not freeze overnight, and wrap the tubs with fleece.
Are the garden chrysanthemums hardy?
No later than November, but before the first night frost, you need to overwinter them in an unheated room or greenhouse. The temperature in the winter quarters should definitely be below 7 degrees Celsius, otherwise it will encourage resprouting. Young shoots are particularly sensitive to frost and will freeze when planted in the spring, which, of course, will negatively affect the growth of the plant. However, if the room temperature remains below 7 degrees Celsius, then the plant will not resprout.
Garden chrysanthemums are planted out in the garden in the spring, and then form their root system during the summer months. The flowering period can vary greatly from variety to variety, but for most it begins in late August / early September and ends around November / December.
So if you have planted out chrysanthemums in the bed in the spring, they are the hardy kind. However, you need to prepare the perennials in the fall for the coming winter. For this purpose, proceed as follows:
- During the flowering period, regularly pluck off the withered (preferably once a week).
- After the end of the flowering period, the above-ground parts of the plant dry out and the leaves and shoots turn brown. This is the right time to make a nurturing pruning.
- The shoots are shortened to a quarter of their length. Ailing shoots are removed completely. The plants are also checked for pests and diseases and, if necessary, treated before pruning.
- To protect the delicate roots from frost, the flower bed is mulched with fir brushwood.
Do not confuse autumn asters and chrysanthemums!
Before considering how to get your chrysanthemums through the winter, be sure the flowers in the bed are really chrysanthemums. All too often, fall asters and chrysanthemums are confused. It’s no wonder, since the two types of plants are close relatives and look very similar. However, they have different hardiness.
- Autumn chrysanthemums in pots are not hardy. They are grown as annual flowers and rarely overwinter indoors.
- Winter asters, or garden chrysanthemums, are hardy but must be cut back in late fall and need additional frost protection with mulch during the winter months.
- Autumn asters are very hardy and can easily withstand temperatures as low as -40 degrees Fahrenheit. Wind, rain and snow do not bother them. Therefore, the flowers are not cut back after the end of flowering. All the more so – the shoots should definitely remain standing, because they protect the roots from frost and cold.
How to recognize the autumn asters: They bloom before the garden chrysanthemums. If the flowers in the container on the balcony or in the flowerbed have already faded in mid-October, then they are probably autumn asters. But if they just start to bloom in mid-October or are in full bloom, then they are probably garden chrysanthemums.