Using a greenhouse isn’t just about growing delicious tomatoes – you need to know how to keep it in tip top condition to get the best out of your plants. Like any building, a greenhouse needs maintaining. Use our tips to keep your greenhouse in good condition.
Once a year you should give your greenhouse a really good clean – this will make sure the glass allows the maximum amount of sunlight in, and prevent nasty pests and diseases from being allowed to take hold.
The best time to clean your greenhouse is early spring, after the worst of the cold weather but before you start planting seeds.
Start by removing everything that isn’t bolted down from the greenhouse. Make sure you pick a mild day if you have overwintering plants so that they don’t get damaged by the cold. If you’re worried, wrap delicate plants in fleece or move them to a shed or porch where they will be sheltered. If you have heaters in your greenhouse, make sure they are switched off and removed if possible, and the electricity is turned off.
Get rid of as much rubbish as you can, throwing out used growbags (empty the compost into a compost bin or onto the garden), and sweeping up dead leaves and spilled compost. Give your plants a good once-over too, removing any dead, damaged or diseased leaves. Be brutal and throw away any plants that are too far gone to survive. Disease can spread easily in a greenhouse so make sure you dispose of every infected leaf.
If you have plant beds in your greenhouse, give them a good weed and dig over, checking for grubs, slugs and other pests.
Wash the windows and all other surfaces in the greenhouse with a mixture of detergent and warm water. Jeyes fluid is ideal for cleaning with as it will disinfect and destroy diseases, as well as cleaning as it goes. Use a sponge with a scourer on one side so you can scrub at any stubborn stains. Change your water regularly so that you’re not just spreading the dirt about!
Wash down all of the pots, tables etc that you’ve removed from the greenhouse too, making sure you do this somewhere away from plants that could be harmed by the strong disinfectant.
Clean the outside of the greenhouse in the same way, using a mop or a sponge attached to a stick to reach the roof. Make sure you clean any old leaves, moss and gunk out of the gutters while you are washing the outside.
Frame and Base Maintenance
While you’ve got the greenhouse as empty and clean as possible, it is a good idea to check over the frame and base to see if anything needs fixing.
Ensure the base of the greenhouse is solid, and that the frame is securely fixed to it. Check for any small gaps where draughts and pests might get in, and seal them up with exterior sealant.
Next check the frame over. If the frame is aluminium, check the joints to make sure no bolts are loose, damaged or missing. Look over the windows, ensuring that all of the clips holding the glass in place are there, and in the correct positions.
If your greenhouse has a wooden frame, a bit more maintenance is required. Wooden frames need repainting every other year or so. If you are repainting, wash down the wood if you haven’t already done so, and go over it with sandpaper. Check for any signs of rot and woodworm as you go over the frame and treat with wood treatment solution if needed before painting.
Replacing Broken Panes
If any panes of glass are cracked or broken you should replace them. This is a very simple job if you have an aluminium-framed greenhouse. The pane will be held in with metal clips - use a pair of pliers to grip the clip and unslot it. Do this for all the clips holding the pane in, making sure to support the glass so that it doesn’t fall out once you’ve removed all the clips. If a lower pane is damaged, you may find that it is holding a higher pane in place so you’ll need to remove both to start with. You can put the undamaged higher pane back in place of the broken lower one.
Have a glazier cut a new piece of glass or plastic to replace the old broken one, and make sure the plastic seal is in place before fitting the new pane in place.
For wooden-framed greenhouses the job of replacing broken panes is slightly trickier – the glass is usually held in with putty or sealant on the outside and metal pins (also called brads) on the inside. Use pliers to pull out the pins – taking out just as many as you need to in order to slide the pane out safely. You may find that the putty or sealant on the outside holds it in place a bit too well, so use a craft knife to break the seal. You’ll need to replace the sealant once you have your new piece of glass in place anyway, so remove all the old material while you have the glass out.
Once you have your new pane ready, put it in place and very carefully hammer new pins into the frame to hold it in place. Apply new putty or sealant to the outside of the frame to seal the pane in.
Shading and Ventilation
While the point of a greenhouse is to provide a nice warm, light environment for your plants, in the summer it can get a bit too hot so it’s important to provide ventilation and shading to protect your plants.
You can use old net curtains, special roll-up shades, or opaque plastic to line the windows and protect your plants from the sun when needed. Another option is a special shading wash that covers the glass, and can be washed off in the autumn.
Automatic openers can be fitted to windows and vents so that when the temperature in the greenhouse gets too high, the window will open by itself. When the temperature goes down again at night, the window will close itself so you don’t need to worry about it.
Let spiders and ladybirds into your greenhouse as they will eat all sorts of nasty pests for you.
Keep a tray of water on the floor of the greenhouse to raise humidity.
Don’t shock tender young plants by watering them with cold water – keep a container of water inside the greenhouse so that you have warm water to give your plants.
Use bubblewrap to line the greenhouse during winter, as this will help to insulate it and protect your overwintering plants from the cold.
All project content written and produced by Mike Edwards