Greenhouse Maintenance and Cleaning

A greenhouse isn’t just for growing tasty tomatoes, it’s essential to maintain it to ensure your plants thrive and to ensure this, regular upkeep keeps your greenhouse in great shape and creates the ideal environment for healthy growth.

Follow our simple tips and steps below to keep your greenhouse performing at its best.

Cleaning Your Greenhouse

Give your greenhouse a deep clean once a year to maximise sunlight, prevent pests, and stop diseases from spreading. The ideal time to clean is early spring, after the coldest weather but before planting season begins.

When cleaning your greenhouse, work through the following steps:

• Step 1: Clear Out the Greenhouse: Remove everything that isn’t fixed in place. On mild days, move overwintering plants outdoors or into a sheltered area. Wrap delicate plants in fleece if necessary. Turn off and remove heaters, ensuring the electricity is off for safety. Dispose of old grow bags, sweep up debris, and check plants for dead or diseased leaves, discard any infected or unsalvageable plants to prevent disease spread.
• Step 2: Clean Inside the Greenhouse: Wash windows and all surfaces with warm, soapy water or a disinfectant like Jeyes Fluid to eliminate dirt and germs. Use a sponge with a scourer for tough stains and change water frequently to avoid spreading grime. If you have built-in plant beds, weed and turn the soil while checking for pests like slugs and grubs.
• Step 3: Clean Removable Items: Thoroughly wash pots, tools, and tables outside the greenhouse, keeping them away from plants that could be harmed by disinfectant. Rinse well and let them dry before returning them to the greenhouse.
• Step 4: Clean the Greenhouse Exterior: Wash the outside using a mop or sponge on a stick to reach the roof. Clear gutters of leaves, moss, and debris to ensure proper drainage. A clean exterior allows more sunlight to enter, benefiting your plants.

Frame and Base Maintenance

After a harvest, your greenhouse should be fairly clear and empty, so this is an ideal opportunity to do a full inspection of the frame and base for any necessary repairs.

Starting with the base, ensure it is solid and the frame is securely attached. Seal any small gaps with exterior sealant to block draughts and prevent pests from entering.

For aluminium frames, check all joints to ensure bolts are tight and intact. Inspect the window clips to confirm they’re present and properly positioned to hold the glass securely.

Wooden frames require more upkeep. Repaint or treat (varnish, oil, timber sealant etc.) the frame every two years to protect it.

Before painting or treating, clean the wood, sand it down, and inspect for signs of rot or woodworm. Treat any affected areas with a wood treatment solution, then apply a fresh coat of paint for durability.

To summarise what needs to be done:

• Treat or Paint: Timber framed greenhouses require a fair bit of upkeep, so need to be painted or stained, ideally every year or at least every other year. Although rare, aluminium/galvanised greenhouse frames can corrode, so any such areas should be removed and paint added to prevent it occurring again
• Tighten Bolts/Fixings: Check all the bolts/fixings of aluminium greenhouses. Over time they can become loose and cause gaps etc. so any loose bolts/fixings should be tightened
• Check Clips: Again, on aluminium/galvanised greenhouses, the glazing/panes are clipped in so check all clips and ensure each pane is correctly and securely clipped in
• Inspect Base: Even aluminium/galvanised greenhouses can corrode, so where the base is sat on potentially damp ground or base it should be regularly check for corrosion etc. This is obviously of high priority for timber bases due to rot
• Fix Gaps: Any gaps can allow heat to escape and pests to get in so gaps and the likes should be closed up or filled

Heaters and Boilers

In some, not all greenhouses, there may be some form of heating and this usually comes in the form of a greenhouse boiler or heater. These are usually parafin, gas or electric.

Whichever solution, they pretty much all provide reliable, adjustable heat and often include thermostats to maintain precise temperatures.

• Gas: Gas heaters, powered by propane or natural gas, are another efficient option, especially for larger greenhouses. However, they require proper ventilation to prevent carbon dioxide build-up
• Parafin: Paraffin heaters are a cost-effective choice for smaller greenhouses. They provide warmth while increasing humidity levels, which can be beneficial for some plants. However, they require regular refilling and monitoring, however they also require decent ventilation due to fumes
• Electric: Electric heaters usually come in the form of tube heaters , these are small, long, cylindrical heaters that put out a fairly decent amount of heat and as they are low wattage, they don’t use too much electricity. As greenhouses can be humid places, there is obviously a risk using electricity in such environments, so ay supplies have to be installed by a professional Part P registered electrician to ensure they are safe
• Solar: For eco-conscious gardeners, solar-powered heaters are an emerging option, using renewable energy to maintain heat

Greenhouse Boilers

Boilers offer an advanced solution for heating larger or commercial greenhouses. They can be fuelled by gas, oil, or biomass, and are connected to a network of pipes or radiators to distribute heat evenly.

Biomass boilers, which use organic materials like wood pellets, are a sustainable option that reduces carbon emissions.

Though boilers require a higher initial investment, they are highly efficient and cost-effective in the long run for substantial heating demands.

Due to the inherent risks involved with any of the above heating solutions, it is of utmost importance that whatever one you use, it is correctly maintained to the highest level to ensure it’s safety at all times.

Glazing and Panels

Replacing cracked or broken panes in your greenhouse is straightforward with the right approach, but a necessary job.

For aluminium-framed greenhouses, panes are held in place by small metal spring clips. Use pliers to carefully remove the clips, ensuring you support the glass to prevent it from falling. If a lower pane is damaged, it may hold an upper pane in place, so you’ll need to remove both. Replace the damaged lower pane with a new one or temporarily use the undamaged upper pane if it fits.

Get a replacement glass or plastic pane cut to size by a glazier. Before fitting, ensure the plastic seal is properly in place to secure the new pane.

Wooden-framed greenhouses require a slightly different process. Here, the glass is usually fixed with putty or sealant on the outside and metal pins (or brads) on the inside. Remove the pins using pliers, but only enough to slide the glass out safely. If the putty or sealant is stubborn, use a craft knife to break the seal. Remove all old putty or sealant before installing the new pane.

Once the new glass is ready, carefully position it and secure it with new pins hammered into the frame. Apply fresh putty or sealant to the outside to create a weatherproof seal and ensure the pane stays in place.

As well as replacing damaged or broken glass panes or panels, it’s also essential to perform regular checks and maintenance on other areas related your greenhouse covering:

• Shading: Some greenhouses feature stick, spray or clip on shading for the summer months to protect plants from direct sunlight, this should be removed for the colder, winter months
• Control Heat Loss: Depending on the age of your greenhouse it may be subject to air leaks, allowing important heat to escape. All such gaps and leaks should be plugged or repaired
• Keep Everything Clean: Ensure that all panes and panels are clean and clear at all times, wash them down with warm soapy water (mild detergent). Ensure as much light can enter as possible
• Check Panels/Panes: As well as repairing and replacing any damaged/broken panes, regularly inspect them to ensure they are in good condition, fully clipped and secured in the frame and unable to move

Shading and Ventilation

Greenhouses are designed to provide a warm, light environment, but during the summer months heat can sometimes become excessive and can actually damage your plants. Proper ventilation and shading are essential to protect your plants from overheating.

When it comes to shading, you have the following options:

• Use old net curtains, roll-up shades, or opaque plastic to shield plants from direct sunlight
• Alternatively, apply a removable shading wash to the glass, which can be easily cleaned off in autumn

As for ventilation, your best options are as follows:

• Ensure you have a thermometer in your greenhouse and open and close any opening windows as required. This is normally when the temperature reaches around 27°
• Alternatively, install automatic window openers to regulate greenhouse temperature. These devices open windows or vents when it gets too hot and close them again as temperatures drop, ensuring consistent airflow without manual effort.
• Ensure all vents and windows are well maintained, oil hinges etc.
• Ensure all windows/vents close tightly and seal. Fit weather seals if required to get a good seal
• Ensure any fans are well maintained and spin freely etc.

Floors and Doors

The floor and door(s) of your greenhouse are highly important areas due to the amount of heat they can potentially loose and the overall impact that this can have on any plants you may have in there.

To ensure that you maintain an even temperature all year around, minimising the amount of cold that can rise up from the ground is a great idea. The best way to do this is normally through adding insulation, however this will really depend on what type of floor you have.

As well as the floor, if you have a poor fitting door this can allow a huge amount of heat to escape, so ensure that any door(s) fit and close correctly with no gaps, or if there are plug them or use sealant strips.

Additionally, ensuring your floor remains in good condition is of high importance, so start by keeping it clean and free from dirt, grime and any algae or lichen growth. Also ensure you repair any cracks that could lead to weed growth and heat loss.

Diseases and Pest

Pests and disease are the bane of any gardeners life and can wreak havoc in an enclosed area such as a greenhouse if allowed to grow and develop so it is of high importance that any such contagions are prevented from developing.

With the above in mind, ensure that you regularly work through the following points:

• Regular Cleaning: Deep clean your greenhouse at least once a year, ideally in early spring. Remove dirt, algae, and old plant debris from windows, floors, and surfaces using warm soapy water or a disinfectant like Jeyes Fluid and sterilise pots, trays, and tools before reuse to prevent the spread of pathogens
• Disinfect Water Supplies: If you have water storage areas, these can harbour algae and insects that can damage crops. Ensure these are kept clean and disease free
• Inspect Plants Before Introducing Them: Check new plants carefully for signs of pests or diseases before placing them in the greenhouse and quarantine any suspicious plants until you’re sure they’re healthy
• Maintain Good Ventilation: Ensure proper airflow to prevent damp conditions, which can encourage mould and fungal growth. Use automatic vents or fans to keep the air circulating effectively and keep humidity levels at a nice constant
• Water Wisely: Water plants early in the day so moisture can evaporate before nightfall, reducing the risk of fungal infections. Avoid overwatering, which can create a breeding ground for pests and diseases
• Introduce Beneficial Insects: Natural predators like spiders, ladybirds or parasitic wasps can help control aphids, whiteflies, and other pests. Try to avoid using broad-spectrum insecticides that might harm these helpful creatures
• Rotate Crops: Avoid growing the same plants in the same spot year after year, as this can allow soil-borne diseases to build up. Use fresh soil or compost annually in pots and beds
• Dispose of Infected Plants: Remove and destroy plants that show signs of severe disease to prevent it from spreading. Do not compost diseased material—dispose of it in sealed bags
• Apply Preventative Treatments: Use organic pest deterrents, like neem oil or garlic spray, to keep pests at bay without harming plants or beneficial insects. Apply fungicides sparingly and only when necessary to avoid resistance build-up

Keeping a clan and well maintained greenhouse is an essential part of any gardening process and by doing so, you are setting yourself well on the way to producing bumper crops!