Deep cleaning a greenhouse

As we gear up for winter, it’s time to address a critical task that should be at the top of every gardener’s to-do list: cleaning the greenhouse. This is usually a job I leave until January, but this year I’m getting it done a bit early as it’s been a heck of a year for pests and I want them eradicated!

Since I’m cleaning my greenhouse, I thought it was the perfect time to take you through how to deep clean yours in order to make it a delight when you start your seed sowing in the new year. I’ll share insights on why deep cleaning is crucial and how to take it a step further with fumigation. So, grab your rubber gloves!

1. The Urgency of Deep Cleaning: Battling Pests and Ensuring Plant Health

It’s my number one essential job, especially as the depths of winter approaches. The primary motivation for this Herculean effort? Pest control. Pests like aphids are known to overwinter in your greenhouse, hiding so a thorough cleaning is needed to eradicate them and their eggs.

2. The Deep Clean Process: A Brush and Wipe-Down

I always start with an emptied greenhouse – a necessary evil so that I can get to all the nooks and crannies unhindered. So the first thing I do is take everything outside, well everything that I can get out of the greenhouse anyway. Then armed with a good brush, the cleaning adventure begins from the top down. The focus is on the frame, glass, and all the hidden channels where pests love to hide. Really focus on giving everything a good brush down.

Why It’s Necessary:

  • Thorough Inspection: A deep clean involves a meticulous examination of all surfaces, revealing hidden pests like snails and slugs and lets you learn about those places they like to hide so that you know where to keep an eye on throughout the year.
  • Preventing Future Infestations: By clearing out potential hiding spots, you’re reducing the risk of pests making a massive comeback early in the next growing season.

2. Grab your bucket and sponge

A good wash, with lots of elbow grease, follows from giving the whole greenhouse a brush. This is your chance to scrub away all the grime and dust and of course any nasties. Get that glass sparkling! Now you can buy greenhouse-specific cleaners for doing this but I confess that I don’t bother, I just get in there with household soap. Don’t use your favourite sponge though, you’ll never want to take it indoors again after you are done.

Why It’s Necessary:

  • Light levels: dirty glass will reduce the amount of light coming into the greenhouse and therefore the amount of light your plants can get.
  • Cleanliness: not only will you be scrubbing off the general dust and dirt, but you will also be scrubbing away any unwanted grime like honeydew, and the sticky secretion left behind by aphids. This can be a breeding ground for mould if you leave it.

3. Disinfecting for a Fungus-Free Zone

If you are not looking to go for the full-on deep clean, but want to make sure your greenhouse is clean and ready for the coming year, you can stop now, give the whole greenhouse a rinse down and you are good to go. However, for a proper deep clean to deal with dirt, pests and potential mould and fungus, the next step is to disinfect it. All those crevices I mentioned are the perfect spot moulds and fungus.

As with the various cleaning solutions you can buy, you can also buy greenhouse-specific disinfectants if you want to, some smell all lovely and citrussy. However, any decent disinfectant will do the job. The most commonly used here in the UK is good old Jeyes fluid.

You can treat this as you did the soap wash and apply it with a bucket and sponge. I actually prefer to do this using my garden spray bottle, that way I can direct jets of it into all those hard to reach places.

Why It’s Necessary:

  • Fungus Prevention: Disinfecting helps eliminate any remaining spores or fungal elements that might have survived the cleaning process.
  • Creating a Healthy Environment: A fungus-free environment is vital for plant health, preventing diseases that thrive in damp and undisturbed areas. This is especially crucial when you are growing from seed or working with young plants which are susceptible to fungal diseases.

4. Drying: The Final Touch

It’s obvious once someone says it, but don’t forget to give everything a good dry-off with a hand towel and some fresh air when you are finished. You’ve gone to all this effort, you don’t want to just recreate a damp, warm place for things to grow.

5. Exterior TLC: Ensuring a Clean and Functional Greenhouse

The cleaning extravaganza doesn’t stop at the greenhouse’s interior. You want to get our and scrub that glass and frame outdoors too. The glass outdoors will be way dirtier than the glass inside, so get the elbow grease to work with a bucket and sponge on that too. Remember things like gutters. Give them a good spray with the jet on your garden hose to clear out any debris.

Top Tip: If your gutters are connected to a water butt, remember to unhook the butt before you clean, you don’t want that soapy water ending up in the water butt.

Why It’s Necessary:

  • Light Transmission: Clean glass on the exterior maximizes sunlight penetration, contributing to the overall health of your plants.
  • Functional Gutters: Clean gutters ensure proper water drainage, and in this case, feed into a water butt for sustainable water use.

6. Fumigation: A Game-Changing Finale

A new element I added this year that I haven’t in previous years is to fumigate my greenhouse with a smoke bomb. You do get lots of types of smoke bombs for this very purpose. You use them to kill pests which are harbouring in the greenhouse and to kill spores. They are usually quite severe though, often highly toxic to you and your plants. This year I wanted to try one out to battle the aphids which were actually on my plants so I wanted something that was safe to use. Hence I’ve tried out a garlic smoke bomb. It stinks and is very unpleasant but it’s not dangerous to use and doesn’t damage plants so I’ve given this a test.

So far so good, I can see a definite reduction in aphids and a lot of dead ones… but only time will tell how effective it’s been.

Why It’s Necessary:

  • Comprehensive Pest Control: Fumigation targets pests that may have escaped the initial cleaning stages, ensuring a thorough eradication.
  • Plant-Friendly Approach: Unlike some fumigation methods, a garlic smoke bomb allows plants to stay inside, making it a convenient and safe option for the greenhouse ecosystem.