Glasshouses, plastic greenhouses, polytunnels and garden frames are all candidates for periodic cleansing.

Greenhouse cleaning is best done with regard to the plants being grown:

• For summer cropping such as tomatoes: clean in winter when the crop has been cleared
• For all year round plants such as orchids: clean in mild spells in autumn to improve light transmission as winter approaches
• For periodic and successive crops, raising seedlings for example: clean in periods between crops such as autumn or spring

Set aside a good day for the task, ideally in dry, calm weather, then;

1. Remove plants – a sheltered area with fleece protection is a suitable to hold plants while cleaning is carried out
2. Brush or vacuum to remove all debris for destruction or removal from the garden
3. Clean the structural parts with disinfectant or detergent (hot solutions are often best – consult manufacturers directions for use)
4. Glazing material should also be washed inside and out, but for plastic materials test on a small inconspicuous area first to be sure the cleaning material does not damage the glazing. Scrub off any old shade paint on the outside of the glass from the summer
5. Ease out dirt trapped between panes using a flexible scraper such as plastic plant label
6. Replace broken parts such as vent controllers and draught excluders
7. Pay attention to propagation areas and equipment. Young plants are especially vulnerable to diseases

Cleaning out gutters and water butts

At the same time as cleaning the greenhouse structure, it is also usually a good idea to clean out other structures such as;

Gutters

These block easily with detritus so cleaning them out ensures the free flow of water and limits build up of unwanted material in water butts.

1. Put on a pair of rubber gloves and run your hand along the inside length of gutter
2. Scoop out any old leaves, moss and other debris that has accumulated
3. Pay particular attention to the top of fall pipes – these may need unblocking with the aid of a wire coat hanger
4. Sluice away remaining dirt with a hosepipe or watering can, diverting water to a bucket for disposal around trees and shrubs
5. Place a wire mesh cap where the gutter meets the fall pipe to trap leaves and other larger debris. Clean this out regularly, especially after leaf fall
6. Put any debris on the compost heap

Water tanks or water butts

Standing water in butts can become green with algae and may be a source of water borne root rots such as Phytophthora. Uncovered tanks may harbour mosquitoes. Ideally they should be cleaned out once a year.

1. Drain out any water by tipping the butt on its side to clear dregs and enable access for cleansing.
2. Scrub out the inside of the butt or tank with a coarse brush, if accessible, then use a proprietary cleaning product and rinse again. Water butt cleaners containing naturally occurring microorganisms are available. Tie a brush to a stick to reach into areas that are otherwise inaccessible.
3. Rinse with clean water.
4. Water that is discoloured or smelly will not harm plants, although it is good practice to use tap water for vulnerable seeds and seedlings.
5. Fit filters to rainwater diverters to ensure butts are collecting clean rainwater. Old tights make a satisfactory filter where it is not possible to fit more sophisticated equipment.
6. Tight fitting lids that exclude light will help keep butts free of contamination by soil and plant debris. They are also a safety measure for young children and wildlife.

The RHS believes that avoiding pests, diseases and weeds by good practice in cultivation methods, cultivar selection, garden hygiene and encouraging or introducing natural enemies, should be the first line of control. If chemical controls are used, they should be used only in a minimal and highly targeted manner.

Safety: Only attempt to clean gutters and glazing that are safe and easy to reach. Avoid putting your body weight against conservatory or greenhouse glazing. Long handled tools are available for safe working from ground level. Wear eye protection and gloves when handling glass or sharp metal fittings.