How to Clean a Greenhouse: Step-by-Step
A full greenhouse clean takes 2-3 hours and should happen once a year between November and February. Dirty glass blocks up to 40% of available light. Use diluted Jeyes Fluid (1:20 ratio) on all internal surfaces. Clean inside every aluminium channel and scrub pots before returning them. This single annual job prevents pest carry-over and gives your crops the strongest possible start.
Key Takeaways
- Timing: Clean between November and February when the greenhouse is empty of summer crops.
- Tools needed: Hosepipe brush, soft broom, spray bottle, Jeyes Fluid, bucket, sponge.
- Method: Start from the roof down on the outside, then empty and spray every surface inside.
- Pest control: Spray inside aluminium channels where red spider mite and whitefly overwinter.
- Frequency: Once a year minimum. Twice if you had pest or disease problems during the season.
Installer's Note
We clean greenhouses during every installation and repair job. The difference between a clean greenhouse and a neglected one is visible within weeks of the growing season. Algae-covered glass starves plants of light. Pests hiding in the frame channels multiply fast once temperatures rise. A proper annual clean is the single best thing you can do for your greenhouse.
When to clean your greenhouse
The best window is between November and February. Summer crops have finished and overwintering plants are not yet established. Pick a dry, mild day. Cold water on frozen aluminium frames is miserable work and less effective at shifting grime.
We recommend late November or early December. This gives you time to disinfect, dry everything out, and get the greenhouse ready for early seed sowing in January. Planning on insulating your greenhouse for winter? Clean first, then fit the insulation.
What you need
Gather everything before you start. Nothing wastes time like hunting for supplies mid-job.
- Hosepipe with brush attachment — a car-wash brush works well for the outside glass.
- Soft broom — for sweeping down internal walls and corners.
- Spray bottle — even a cheap one from a pound shop does the job.
- Jeyes Fluid — dilute 1:20 with water for general disinfecting.
- Bucket, sponge, and washing-up liquid — for glass and frame surfaces.
- Old toothbrush or bottle brush — for getting into aluminium channels and glazing bars.
- Garden disinfectant or white vinegar — for pots and staging.
How to clean the outside
Start at the roof and work down. Gravity does half the work for you. Wet the entire structure with the hosepipe first to loosen dirt and algae.
Mix a bucket of warm water with a squirt of washing-up liquid. Use a long-handled brush to scrub the roof panels. Pay attention to the overlap joints where two panes meet. Algae builds up in these gaps and wicks moisture into the frame.
Work down each side panel, then do the end walls. Rinse everything with clean water. Add a tiny drop of detergent to the rinse water. This helps prevent streaking as the glass dries.
While you are outside, check the greenhouse base for cracks or movement. Winter frost can shift concrete pad bases and push dwarf walls out of alignment.
How to clean the inside
This is the important part. The inside is where pests and diseases overwinter.
Start by emptying everything. Remove all pots, trays, tools, and bags of compost. Take out removable staging and shelving. You need bare surfaces to clean properly.
Sweep down the entire interior with a soft broom. Get into every corner. Remove spider webs, dead leaves, and any debris behind the staging area.
Fill your spray bottle with diluted Jeyes Fluid (1 part Jeyes to 20 parts water). Spray every surface you can reach. Pay special attention to the nooks and crannies where the glass meets the frame. These hidden gaps are exactly where red spider mite, whitefly, and scale insects hide through winter.
Use a sponge dipped in the same Jeyes mix to wipe down all internal glass panels. Work methodically from one end to the other so you do not miss any panels.
While cleaning inside, keep an eye out for plants that damage greenhouse frames. Climbing plants and self-seeded weeds growing against the base can trap moisture and corrode aluminium over time.
Cleaning the glass
Different glazing types need different treatment. Using the wrong method can cause permanent damage.
Horticultural glass: Standard soapy water and a sponge. You can use a squeegee for a streak-free finish. Horticultural glass is thin, so avoid heavy pressure. For a full method, see our guide to cleaning greenhouse glass.
Toughened safety glass: Same method as horticultural, but it handles more pressure. You can scrub harder on stubborn algae patches without worrying about breakage.
Polycarbonate panels: Never use abrasive pads or scouring agents. Polycarbonate scratches easily. Stick to a soft cloth with soapy water. Rinse well. Scratched polycarbonate loses clarity permanently.
Dealing with pests during cleaning
Cleaning your greenhouse is your best form of greenhouse pest control. Several common pests overwinter inside the structure.
Red spider mite hides in cracks in the frame and under staging. They survive freezing temperatures in their dormant state. Jeyes Fluid spray kills them on contact.
Whitefly tucks into glazing bar channels and the underside of shelving. A thorough clean in November breaks the breeding cycle before spring.
Slugs and snails shelter under pots, in corners, and beneath bags of compost. Removing everything from the greenhouse exposes them. Pick them off and dispose of them.
Vine weevil larvae live in compost. If you had vine weevil damage last season, do not re-use old compost. Bag it and bin it.
Washing pots, staging, and accessories
Every pot going back into the greenhouse should be clean. Old compost and plant residue harbours disease spores. Soak pots in a bucket of garden disinfectant or a 1:10 white vinegar solution for 20 minutes. Scrub off any algae and rinse with clean water.
Staging and shelving should get the same treatment. Wipe down every surface with Jeyes solution. Check metal staging for rust spots. A wire brush and a coat of cold galvanising spray will stop rust spreading.
Clean and oil any vent mechanisms. Check that automatic vent openers still work. The wax cylinders in auto vents lose effectiveness after 3-5 years. If yours are sluggish, now is the time to replace them.
Matt's Tip: The One Thing Most People Skip
After 16 years of fitting greenhouses, I can tell you the most overlooked spot. It is inside the aluminium glazing bar channels. Pop off the glazing clips, slide the glass out slightly, and spray Jeyes Fluid right into the channel. This is where red spider mite colonies sit all winter. If you skip this step, thousands of dormant pests will hatch the moment temperatures hit 15°C. Five minutes of extra effort here saves weeks of pest battles later.
Matt's Tip: Check Your Auto Vents While You Are In There
Every time I clean a greenhouse, I test the automatic vent openers. Hold the cylinder in your hands for 30 seconds. You should feel it start to expand from your body heat. If nothing happens, the wax is spent and the vent will not open next summer. Replacing a vent cylinder takes two minutes and costs under £20. An overheated greenhouse in June costs you an entire crop.
How often should you clean a greenhouse
Once a year is the minimum. We recommend a full clean in November or December every year without exception.
If you had pest problems during the growing season, do a second lighter clean in early spring. Focus on spraying the channels and frame joints where pests are most likely to survive.
Glass-only cleaning can be done more often. Wiping the glass in early spring restores light levels after winter grime builds up. Even a quick wipe in February makes a noticeable difference to seedling growth rates.
Frequently asked questions
What is the best way to clean a greenhouse?
Empty it completely, then scrub every surface with diluted Jeyes Fluid. Start outside from the roof down with soapy water. Inside, spray all frame channels and glass panels with a 1:20 Jeyes solution. Clean all pots and staging before returning them. The whole job takes 2-3 hours for a standard 6x8ft greenhouse.
Can I jet wash my greenhouse?
Use low pressure only and keep the nozzle 30cm from the glass. High pressure can blow out glazing seals and crack thin horticultural glass. It also forces water into frame channels, causing corrosion. A hosepipe with a brush attachment is safer and just as effective for most greenhouses.
Can I use Jeyes Fluid to clean my greenhouse?
Yes, Jeyes Fluid is our go-to disinfectant for greenhouse cleaning. Dilute it 1 part to 20 parts water. Spray all internal surfaces, channels, and frame joints. Rinse with clean water afterwards. Let the greenhouse air out for 24 hours before returning plants. Always follow the dilution instructions on the tin.
Can I use vinegar to clean a greenhouse?
White vinegar works well for glass and removing mineral deposits. Mix equal parts vinegar and water in a spray bottle. It shifts algae and limescale effectively. Vinegar is a good choice if you want to avoid chemical disinfectants. Rinse all surfaces afterwards. For stubborn stains, use it undiluted on a cloth.
How do I clean my greenhouse roof?
Use a long-handled brush from ground level wherever possible. A telescopic car-wash brush on a hosepipe reaches most greenhouse roofs safely. Work from one end to the other in overlapping strokes. For glass roofs, finish with a squeegee. Never stand on greenhouse glazing bars. They are not designed to bear weight.
Can I use bleach to clean my greenhouse?
Bleach works but is harsher than necessary for most jobs. If you do use it, dilute one part bleach to ten parts water. Wear gloves and eye protection. Rinse every surface thoroughly. Bleach residue kills beneficial soil organisms, so keep runoff away from planted beds. We prefer Jeyes Fluid because it is formulated for garden use.
