Winter damp is my main memory of December. Where I am, the clear and cold skies of late November turned to December mist and fog, bringing the perils of damp and rot to garden furniture, building and plants. This isn't weather that invites us into gardens or summer houses, but damp weather means it is important to go out there and take steps to reduce the risk and damage that damp can cause.

winter damp

Reduce the risk of winter damp on and inside garden buildings. A gardener's shed by the village hall in Muir of Fowlis. Stanley Howe. Licensed for re-use under Creative Commons attribution share alike 2.0 Generic licence

During the winter we tend not to open shed doors or windows wide, but unless you do damp will get into garden furniture, tools and stores. Safely stored furniture starts to look unloved, rust attacks metal, sheds go green with mould and mildew, and plants die.

And it gets worse. Plant cuttings taken in summer and autumn will rot quickly in a damp and airless shed or on a garage window sill or in a greenhouse with constantly closed doors. Overwintered plants stored safely at the back of the garage or shed without any air moving around them are likely to develop mould and die.

So, far from cheery but always practical, here are three things you can do to reduce the risk of damp spoiling your garden buildings, their contents and your precious plants.

Help moisture escape

  • On dry days open windows and doors, and all the better if there is a breeze to stir the air.
  • Let the air get in and around furniture and tools by clearing away clutter (read our blog on charities that welcome your unwanted tools) and don’t let furniture lean against walls.
  • Clear air vents in roofs and walls (keeping mice screens in place) and ensure there is a through draft (clear away more clutter!).
  • If your summer house or shed is in a very damp spot you may want to consider some more serious steps: install an extractor fan or ceiling fan, regularly use a dehumidifier, or - if you can - store precious garden furniture somewhere else.

Reduce the sources of winter damp

  • Sweep away the garden leaves, moss and twigs that have walked into sheds and summer houses on your shoes and boots. Store bags of potting compost outside, not inside, buildings.
  • Make sure gutters and downpipes are not leaking against shed walls or roofs
  • Repair cracks and holes in roofs or walls.
  • Clear any build-up of moss or general garden gunge from the base of walls and doorways. And if the garden is growing higher than the floor, dig the garden back to a level below the floor.

Don’t overwater plants, but ensure moisture and air

  • Overwintering tender or young plants don't need very much water. Giving them too much or letting them sit in water, is a sure way to kill cuttings, young and tender plants.
  • Fill plant saucers with gravel that lift the base of the pot above any water that drains into the saucer.
  • Know the signs that plants need moisture or humidity around them, not water in their pots: the tips of leaves are brown or shrivelled and the edges of leaves are wilting or yellowing.
  • Create just enough moisture by very lightly spraying leaves, or by putting plants into groups together, or by placing plants on saucers of wet gravel. But only do all this if air can move around the plants, because if it can't you have created ideal conditions for mould.
  • Don’t forget: those lovely pelargoniums of summer days that you are overwintering after you read our blog on how to do it need hardly any water in winter, so don’t kill them with what you think is kindness.


winter damp

Protect your summer's pelargoniums from winter damp to enjoy them next year. Sarah Buchanan