How to Overwinter Pelargoniums Successfully

Pelargoniums are tender perennials that will not survive a frost outdoors in most temperate climates. They must be brought inside before the first frost in autumn — typically in October in the UK — and kept in a frost-free environment until they can go back out in late spring. Getting overwintering right allows you to carry plants forward year after year, building up large, mature specimens that would be expensive to replace each season.

When to Bring Pelargoniums Indoors

Bring pelargoniums inside before the first frost. In most UK gardens this means mid-October at the latest, though in colder northern areas mid-September is safer. Do not wait until a frost warning — cold, wet autumn conditions can cause blackleg and root rot even without actual freezing. Monitor weather forecasts from September onward and act early. A light frost may not kill the plant outright, but it damages stems and leaves, making the plant much more vulnerable to disease during storage.

The Bare-Root Method

The traditional approach is to shake all the compost from the roots, cut back the top growth by about half, and store the plants bare-root in paper bags in a frost-free shed, garage, or cool room at around 5–10°C. The absence of compost reduces the risk of botrytis and root rot. Check the plants monthly, discarding any that have rotted. In late February or March, bring the roots out, pot into fresh compost, water sparingly, and place in a bright, slightly warmer spot to restart growth.

Potted Storage Under Cover

An alternative is to keep plants in their pots, cut back by one-third to a half, in a frost-free greenhouse, conservatory, or light room. Reduce watering to the absolute minimum — once every three to four weeks is usually sufficient at temperatures below 10°C. Stop feeding entirely until growth resumes in spring. This method keeps plants in slightly better condition through winter because the roots are not disturbed, but requires more space and greater vigilance against botrytis and overwatering.

Taking Cuttings as Insurance

Before bringing plants in, take a batch of cuttings in August or September. Young rooted cuttings are much easier to overwinter than large parent plants — they take up less space, need virtually no water, and are very resistant to botrytis if kept cool and dry. Even if the parent plant does not survive the winter, you will have vigorous young plants ready to pot on in spring. Cuttings taken in late summer root within four to six weeks and can then be potted into 9cm pots for winter storage.

Spring Restart

From late February, gradually increase warmth, light, and water to wake stored plants. Repot into fresh compost — overwintered compost is often exhausted and compacted. Cut back any remaining brown, dead stems and remove all old leaves. Begin feeding with a balanced liquid fertiliser when new growth is established. Do not rush to put plants outside: harden off gradually over one to two weeks of daytime outdoor exposure before leaving them out overnight, and only once night temperatures are reliably above 10°C.