The enclosed (and often heated) atmosphere of the greenhouse allows diseases and pests to become more easily established than they would outdoors, and so it should be kept clean all year round to ensure the plants have a healthy environment in which to thrive. A major clean and disinfection of surfaces and equipment in autumn should also be carried out to minimise the risk of overwintering pests and diseases.

Before starting any cleaning work, turn off the electricity supply at the mains, cover any sockets with plastic or polythene bags and remove all plants to a safe place.

Spring

Clear away any plant debris and scrub the inside of the greenhouse with garden disinfectant. Rinse surfaces down with clean tap water. Shading paint may be applied in late-spring.

Autumn

Autumn is the best time to undertake a major clean of the interior, as the weather is still mild enough to allow you to leave tender plants outside whilst the work is being carried out.

Remove shading washes by rubbing them with a damp cloth or a brush. Dirt should be removed using clean water and a long handled brush, although you may find you achieve better results for ingrained dirt by brushing on a solution of kettle descaler. Make sure that you wear goggles and gloves when applying the solution, and then use clean water to rinse the glass thoroughly.

Dirt often becomes trapped between overlapping panes. Loosen this dirt and algae by pushing a long plastic plant label in between the gap and then wash away using clean water.

Clean glazing bars by scrubbing them with fine wire wool soaked in a disinfectant solution; use a brush for anodized aluminium to prevent the surface from becoming damaged. Brickwork, flooring, staging and shelves may also be cleaned with a garden disinfectant; make sure that you use gloves and goggles to protect your skin and eyes.

You may also want to use this opportunity to fumigate the greenhouse with fungicidal and insecticidal smoke. Bring the plants and equipment back into the greenhouse and make sure that all vents and windows are firmly closed. Light the fumigant, taking care not to inhale the smoke, and then leave the greenhouse until it is safe to re-enter. Read the instructions on the fumigant carefully; some types may require you to remove plants before using.

Winter

In the winter, keep the greenhouse clean by removing any debris. Make sure pots and seed trays are ready for spring use by soaking them in diluted garden disinfectant, rinsing them thoroughly with clean water.