GARDENING: Greenhouse cleaning is a necessary evil

If you have a greenhouse, or any structure that you're going to be overwintering plants in, your number one priority is making sure it's clean.

Friday, 7th October 2016, 5:15 pm
Updated Tuesday, 25th October 2016, 3:44 pm
Alpines and geraniums in an unheated greenhouse can rot with excessive winter wet.

Not only must it be frost-free, but pest-free.

Cleaning the greenhouse and conservatory is my least favourite job, but a necessary evil.

Last year's greenhouse cleaned and emptied - apart from tomatoes.

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My plants suffered a couple of years back from aphids overwintering in cracks and crevices, as I couldn’t get to out-of-the-way places in my packed conservatory.

Here’s what you need to do to reduce the risk of there being pests:

1. On a mild day, take everything possible outside.

2. Scrub off any old shade paint from the summer.

Loads of Green Zebra tomatoes still in the greenhouse, which means cleaning is going to be delayed.

3. Brush or vacuum surfaces to remove all debris.

4. Hose down the exterior and interior on a soaker setting, to loosen any pests/eggs and lichen.

5. Wash down glass with warm soapy water and a sponge. A breezy day will mean it dries out more quickly.

6. Spray all surfaces with Citrox, a powerful organic citrus extract disinfectant for cleaning greenhouses, pots, staging, tools, seed trays, bird feeders and bird baths. It doesn’t harm plants and it’s effective against bacterial and fungal diseases.

Last year's greenhouse cleaned and emptied - apart from tomatoes.

7. Glass is best done with an anti-bacterial washing-up liquid – it doesn’t streak.

8. Check that all ventilation panels/windows are working.

9. Finally, check over plants that you’re overwintering carefully BEFORE bringing them in – you don’t want them to be harbouring pests. Better to cut things like geraniums back outside first - and check pot rims and bases for hidden slugs, snails and vine weevils.


Loads of Green Zebra tomatoes still in the greenhouse, which means cleaning is going to be delayed.

Move alpine troughs to a covered porch or lean-to to protect them from the rain. Pick over alpines regularly, removing debris and covering dead patches with extra grit to encourage re-growth.

Ventilate greenhouses and conservatories on warmer days, but keep windows shut at night.

Greenhouses can be insulated using plastic bubble wrap. This will cut down the heating bills, but make sure to minimise the amount of light blocked out by strips of tape etc, as the wrap itself will reduce light levels.

Put cloches over tender herbs like basil, coriander and tarragon, or pot up to move under glass. Pot up mint, chives and parsley to keep on a bright window sill.

Plant autumn garlic, onion and shallot sets.

Replant hanging baskets with spring-flowering bulbs, winter heathers, trailing ivies and spring bedding plants.

Raise patio containers on to bricks or purpose-made pot feet to avoid them sitting in water.

Powdery mildew may be a problem. Cut back fading growth, rather than spraying, which is less effective at this time of year.

Digging the soil, especially bare patches or newly-cultivated land, will expose pest larvae and eggs to birds, as well as clearing weeds and improving soil structure. Don’t leave soil uncovered for too long, however, as it runs the risk of erosion.

It’s an ideal time for moving and planting trees, shrubs and climbers, as well as for hedge planting.

Check tree ties and stakes before winter gales.

Bare-rooted deciduous trees and shrubs are cheaper than containerised plants. You can still order containerised trees and shrubs, and large semi-mature specimens, for planting over the winter.

Shrubs normally pruned hard in the spring such as Buddleja davidii, Cornus alba, and Lavatera, can be cut back by half now, to prevent wind rock and to neaten their appearance.

Place fallen leaves on the compost heap or into separate pens for rotting down into leaf mould. Shredding leaves first with a shredder or mower will help them break down quicker.


For more on these topics, plus cook what you grow, traditional recipes, North East information, environmental news and more, log on to (now smartphone friendly),, follow me on Twitter @MandyCanUDigIt or you can like me on Facebook at Mandycanudigit