If you’re planning to over-winter your geraniums & pelargoniums please “take with a pinch of salt” anything you hear from well meaning “experts” – often they know an awful lot about a wide range of plants and limited specific knowledge of each species.
If the plants are warm and in good light, they are very likely to continue to grow, and some will even flower, in the winter. So fill all those sunny windows and conservatories with all your members of the pelargonium family!
Over-wintering geranium plants:
- The first thing to consider is if the particular variety is a favourite and is worth spending time and trouble on. If not, let it “take it’s chance” and buy something more agreeable next year!
- You also need to think about whether you have enough space for your quantity of plants. Very few of us have enough frost-free room to keep every plant, especially if they have grown very large. There are three choices:
- Keep the plants as they are, but put into pots.
- Cut back the plants so that they spend the winter re-growing and bushing out.
- Root some new cuttings and leave the old plants to get on as best they can.
- Before bringing your geranium plants inside for the winter make sure you examine them well first. Clean off any dead leaves or dying flowers and look for signs of pelargonium rust. This only affects the zonal pelargoniums but it is getting everywhere nowadays. It first came into the country in 1968 and particularly thrives during a damp summer or autumn. Luckily, this does not seem to infect the plants very rapidly and is easily treatable, so simply removing the affected leaves will be a good control. You could also try spraying with a fungicide called Dithane945, which is obtainable at most Garden Centres.
- Light is very important, which is why if indoors they must be right on the window-sill – if they are only three feet from the window they will get 50% less light!
- During the winter try to keep the atmosphere dry, but not the roots. Because the plants do not go into dormancy they continue to grow and therefore transpire and so need some moisture. Geraniums will often survive a drought, but will not grow and thrive – people growing show plants are careful to ensure their plants roots are moist, but never wet, in the winter. To keep the atmosphere dry it is important to ventilate as often as possible. If you do not allow the air to move, your plants will end up a mouldy, rotting heap. Electric fan heaters are best as they move the air around every time they come on as well, and need little work on your part, thank goodness for a thermostat!
- Geraniums are very economical when overwintered in the greenhouse as they only need to be kept frost free. However, we do recommend if your heating has a thermostat you set it at 5ºdeg;C or 41ºdeg;F. If the stems get the frost then the plant will die and not recover! A porch, sunroom or conservatory are excellent places for the pelargonium family in the winter, and sunny windowsills are suitable.