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Geraniums are popular and easy-care summer flowers on the balcony. What they cannot tolerate, however, are low temperatures. Only a cold night can kill the frost-sensitive geraniums, which is why you should take precautionary measures in good time.

In a nutshell

  • Geraniums are sensitive to frost, only some varieties are a little more tolerant
  • Plant only when there is no danger of frost
  • Protect plants from night frost during the transitional periods
  • Pelargoniums can be overwintered with a little effort

Geranium or Pelargonium

Geranium or pelargonium is often used as a synonym. However, these are different genres. This use as a synonym is sometimes exploited by the trade and hardy pelargoniums or geraniums are offered.
Pelargoniums originally come from Africa and are by no means hardy. They only survive sub-zero temperatures for a short time, but not all night. What does exist, however, are hardy species of the genus "Geranium". Often these are native cranesbills, which are also botanically referred to as geraniums. Although both genera belong to the same plant family, they differ in how sensitive they are to frost.

Notice: If you are not sure which genus it is when you buy it, ask the specialist staff whether the plants are hardy and how long they can actually tolerate frost.

Plant out after ice saints

The geranium is sensitive to frost and should therefore only be planted out when no more low temperatures are expected. This is the case around the time after the last ice saints in mid-May. Regionally, however, it can still get cool after this time and to avoid frost damage, you should protect the plants at night in endangered regions.
The situation is different in regions with a wine-growing climate, for example. Here the geraniums can go outside permanently earlier. There are only two species that are less sensitive to frost and can tolerate lower temperatures for a few hours.
These are:

  • Pelargonium violareum
  • Pelargonium finiterianum

Notice: Although the plants can tolerate slightly lower temperatures, flowers or flower buds that have formed at this time may suffer frost damage and fall off.

Pelargonium finiterianum

Protection against night frosts

If you want to put the geraniums on the balcony early in spring, you should protect the plants from sub-zero temperatures at least at night. As a rule, it is already so warm during the day that there is no longer any risk of frost damage.
You can prevent this at night with simple measures:

  • Cover plants with winter fleece
  • Place plants in frost-free rooms at night

With these simple means, you can leave the plants on the balcony much longer in autumn. However, you should not overlook to protect them in time, because especially in autumn, when the humidity is very high, condensation on the leaves causes great damage.

Overwinter frost-free

Geraniums are actually perennials, even if they come from warm Africa. If you have the opportunity, you can overwinter the plants. However, this requires some preparation. First and foremost, however, you should ensure suitable winter quarters.
Frost-free rooms such as:

  • basement, cellar
  • storage rooms
  • bright cool rooms

The preparations you have to make to overwinter the frost-sensitive geraniums depend on the light conditions available to the plants in their winter quarters.
The following preparatory work must be carried out in bright rooms:

  • heavy cutback
  • remove all flowers and buds
  • check for pests
  • light fertilization
  • constant but moderate watering

If you overwinter the plants in a dark cellar, make these preparations:

  • heavy cutback
  • Remove flowering shoots
  • Conduct pest control
  • keep moderately moist

When wintering in the basement, it is particularly important that you also remove the leaves in advance. In the basement, the plant cannot carry out photosynthesis. This means that over time the leaves will turn yellow and the plant will shed them. Remove the leaves in advance, save the plants a lot of energy.

frequently asked Questions

Should I acclimate geraniums to the temperature in winter storage?

Yes, the plants survive the time in the winter quarters much better if they are already used to the temperature.

When do the plants go into winter quarters?

As long as the plants are not endangered by sub-zero temperatures, they can stay outdoors. If low temperatures are also announced during the day, they should move to their winter quarters.

Can geraniums be overwintered in a greenhouse?

Yes, provided the greenhouse is well insulated and the frost cannot damage the plants at night.

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Garden plants