How To Prevent Algae On A Greenhouse
There’s nothing more satisfying than growing your own plants and vegetables in your very own greenhouse. But just like anything in the garden, a greenhouse may require a little upkeep in order to keep it clean, tidy and in top condition.
One common problem that greenhouse owners face is algae growth – that green-like substance that covers surfaces. Algae can appear on any surface, most commonly found on or around the glass window panels, but also not uncommon to spot on the framing too, and if left unchecked, it can become rather unsightly, block the sun’s natural rays and heat from entering your greenhouse, and in turn, even affect the growth of your plants.
Why does algae grow on a greenhouse?
Algae thrives in environments that are warm, moist and have access to sunlight. Greenhouses provide this type of environment perfectly as they are designed to retain heat and moisture. The sunlight that enters the greenhouse also provides the necessary energy for algae to grow. Algae growth is not only unsightly, but it can also lead to other problems such as mold and mildew, which can cause damage to the greenhouse and affect the health of your plants if left to build up.
How to clean algae off a greenhouse
If your greenhouse has already become susceptible to algae, here’s our easiest way to clean it off. Cleaning algae off a greenhouse is a relatively simple process, but it does require some elbow grease. Here’s what you’ll need to do;
- Mix a solution of warm water and mild soap, any dish soap will do fine. You can also use vinegar but be careful not to use neat vinegar, as being an acid it can damage the framing of your greenhouse, so always use it in a watered down solution.
- Put the solution into a spray bottle (use a separate spray bottle to what you would use to normally water your plants with) and go around the affected areas of your greenhouse spraying the soap or vinegar solution onto any algae areas.
- Leave for 15 minutes to let the solution work its magic.
- Spray a sponge with some of the solution, and use the sponge and go around the greenhouse again, gently rubbing the sprayed areas. Avoid using an abrasive sponge or scourer as they can scratch the surface of the glass and framing.
- Rinse the greenhouse with a hose, making sure to remove all traces of soap or cleaning solution.
- Allow the greenhouse to air dry. You can optionally go around with a dry cloth to buff the windows if you prefer a streak-free, crystal clear finish.
It’s best to do this on a mild-warm day, but one that’s not too hot, as we don’t want the soap or vinegar solution to dry too quickly once sprayed onto the greenhouse – we want it to stay wet long enough to work its magic on the algae.

Tips for preventing algae growth on a greenhouse
Prevention is always better than cure, and there are several things that you can do to prevent algae growth on your greenhouse in the future:
- Clean your greenhouse regularly, at least once per year. Regular cleaning will prevent algae from taking hold and keep your greenhouse looking its best. Many gardener’s choose to do this at the start of the main growing season between February-March.
- Provide adequate ventilation. Good air circulation will help to reduce humidity and prevent moisture from accumulating, which can lead to algae growth.
- Avoid overwatering your plants. Overwatering can lead to excess moisture in the greenhouse, which can contribute to algae growth.
- Use a shade cloth. A shade cloth will help to reduce the amount of sunlight that enters your greenhouse, which will limit the energy that algae needs to grow.
- Apply an anti-algae treatment. There are many commercial products available that are designed to prevent algae growth on surfaces. These treatments can be applied to the glass and framing of your greenhouse to help keep it algae-free.
- Trim any overhanging trees or bushes. Leaves and pollen from nearby bushes and trees can cause algae by getting stuck onto your greenhouse and decomposing, giving the algae a place to grow from. Keeping nearby bushes and trees trimmed, and ensuring no branches overhang the greenhouse is good practice to help prevent algae growth.
In conclusion, algae growth on a greenhouse is a common problem, but it can be easily prevented with regular maintenance and proper care. By following the tips above, you can keep your greenhouse looking its best and ensure that your plants grow healthy and strong. Remember to clean your greenhouse regularly, provide adequate ventilation, avoid overwatering, use a shade cloth, and consider applying an anti-algae treatment to keep algae at bay. Happy gardening!
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