While a greenhouse shouldn’t need to be cleaned quite as much as a 'human house', it is very important to schedule a good cleaning session once or twice a year. Ideal times for carrying out this task might be in late autumn or early spring (the winter can be a time when conditions for disease develop, as insects and pests take shelter in the enclosed space). It really depends on what you plan to grow in your greenhouse, and when. Whether it’s glass or polycarbonate, cleaning the glazing ensures the removal of any algae or buildup, which can affect light transmission levels. Not surprisingly, this can interfere with plant growth and photosynthesis. Particularly during cooler winter months, you want to maximise the amount of light that comes into your greenhouse as much as possible.
Choose a mild, settled day and ideally start the job as early in the day as you can: this way, you will have plenty of time to air the greenhouse out and allow all the areas to dry. Move any plants out of the greenhouse - cover them with fleece or leave them in a sheltered area if necessary. Unplug any electrical outlets and remove any tools, benches etc so that there are no obstuctions.
Many people recommend the use of Jeyes fluid for cleaning greenhouses, but we’d strongly discourage this. Jeyes is a chemical cleaner with a high concentration of tar acids. It’s toxic (potentially fatal if the dose is high enough) to cats for one, and while it’s obviously recommended to dilute it, it’s still not the kind of stuff you really want to be using around plants, garden visitors, beneficial insects etc. A more eco-friendly and organic alternative is Citrox, an odour-free disinfectant that’s safe to use around children, plants and pets. It’s also very effective.
That out of the way, you’ll need a few other things to hand when cleaning your greenhouse. A hose, a stiff brush, a sponge or cloth, a bucket with warm water, a scraper, some wire wool… as well as a long-handled mop or brush for high and hard-to-reach places. Have a spare bucket to hand as well if possible, to save you time emptying and refilling. When it comes to cracks and crevices etc, you might also find it easier using a Citrox spray bottle or adding a mixture to your own spray bottle.
Sweep any dead leaves or vegetation from around the outside of the greenhouse. You can choose to use some Citrox for the outer frame (and it will probably make it easier to wipe away algae or buildup), but warm water and a sponge should suffice as well. Use a stepladder if necessary to reach the roof or areas close to it. A telescopic cleaning hose brush connected to a hose can be very handy for this kind of task. Be careful not to lean on the structure when cleaning the higher sections. While cleaning, look out for any cracks in the window panes. Window panel joints are a hotspot for caked-in or difficult-to-remove dirt. Finish by rinsing the frame so that there’s no visible streaks left on the glazing.
Next, it’s time to turn your attention to the inside of the greenhouse. Firstly, clear away any old or dead plant materials. Use a stiff brush to sweep clear the pathways. Pay attention to any corners and use a vacuum if you have to. Next, you want to take some Citrox and warm water solution and turn your attention to the greenhouse frame. Thoroughly cleaning the windows will ensure that their light transmission is at its highest level. Tackle any nooks or crannies where pests or insects might be hanging out. Wash down any shelving units you have inside. Don’t forget to clean wooden panels or sections and brickwork.
Now is also a good time to wash out and disinfect empty or unused pots and trays: soak them in a Citrox solution for 20 minutes or so and scrub them out, an old toothbrush is very hand for corners. Don’t forget to clean wooden panels or sections and brickwork. When the job is winding down, you’ll probably need to give the floor area another sweep to pick up any scattered debris from the window panes and staging. Leave the door wide open to allow the greenhouse to air out. When you view the frame and glazing after you’ve cleaned it, you should hopefully see a visible difference and the structure will feel ‘renewed’, brighter and ready for some fresh growth. Good luck!