Autumn cleaning of the greenhouse

Clean the inside and outside of the garden greenhouse.

The first step before starting to clean the greenhouse is, of course, to empty it by moving as many items outside as possible. Ideally, do this on a mild, dry, and sunny day to ensure proper ventilation and to remove the plants without subjecting them to thermal shock.

Next, carry out a thorough cleaning of both the exterior and interior of the structure: windows, gutters or downpipes, doors, covers, hoops, etc. For this, you will simply need:

• a bucket of water;
• a brush or scraper;
• a sponge;
• a pair of gloves to protect your hands.

Optionally, you can also use a water hose for rinsing, a squeegee, and a telescopic handle.

In terms of products, we recommend opting for natural solutions: Marseille soap, white vinegar for the windows, or black soap are very effective and much less polluting than bleach, for example. For a disinfecting action, combine them with hot water. During cleaning, make sure to thoroughly remove any traces of soil, moss, algae, mould, and dead leaves, which can affect the lifespan of the equipment.

On the ground, simply sweep or use a hand broom to eliminate sand, dust, and green waste accumulated in the paths or other circulation areas.

This is also the time to remove any shading cloth or shade netting on the windows if there was any, using soapy water and a cloth (some biodegradable products will have already started to break down naturally by the end of the season). This cleaning will allow more light to penetrate throughout the winter, which will be beneficial for the plants that remain in place.

Remove items from the greenhouse, clean them, and clean the surfaces of the greenhouse

Vérifier l’état de la structure de la serre

Autumn is also the ideal season to ensure that all elements of the greenhouse are in good condition and that the structure is still watertight.

To do this, check:

• that the panes are free from impact marks or cracks;
• that the seals are in place and not defective;
• that the hinges are functioning, that the panes or vents open correctly, and that the doors slide smoothly (you can spray a lubricant if necessary);
• that the fixings are still secure;
• for any holes or tears in the covers; take the opportunity to retighten them properly so they withstand the elements better during the cold season.

These checks will also help extend the lifespan of your garden greenhouse, whether it is made of glass or plastic.

Remove the last crops

Cleaning the greenhouse is the time to tend to the plants that are at the end of their cycle.

• For fruits and vegetables: remove any rotten or diseased specimens. The remaining healthy fruits can generally stay in place under the greenhouse until late October to early November, allowing them to continue ripening gently.
• For annuals: remove the dried-up plants that are no longer producing, taking care to remove the entire root system. Cut them into sections and compost them. This is also the time to collect the last seeds that will be used for next season’s sowing.
• For perennials: remove yellowing leaves, faded flowers, damaged branches, and tired plants.
• For climbing plants: prune the stems, especially if these plants usually provide shade in the greenhouse. This will allow more light to penetrate during the winter.

Disinfecting growing containers and maintaining tools

To prevent the proliferation of diseases or pests, and to provide your future sowings with the best growing conditions, we advise you to clean all your containers. Gather seed trays, growing tables, pots, terrines, and planters. Start by removing the used substrate, which you can add to the compost. Then simply use a basin of lukewarm water in which you have diluted some black soap. Immerse the small containers and clean the larger ones with a sponge. Then leave them to dry naturally in the sun.

Don’t forget to clean the additional accessories: stakes, ties, twine, labels, etc. Scrape off the embedded soil using a stiff brush or a spatula.

Autumn cleaning is also the time to take care of your tools, ensuring they are ready for spring and last longer. Using a brush, scrape off the soil and impurities remaining on your spades, forks, shovels, or trowels. Then proceed to clean them, again with a sponge, lukewarm water, and black soap. Dry your tools thoroughly with a clean cloth to avoid any risk of rust. You can then take the opportunity to sharpen the pruning and cutting tools such as pruning shears and care for the wooden handles. To learn more, check out our article “Clean, maintain, and protect your gardening tools”.

Cleaned and stored tools

Taking care of the soil

After clearing away the remnants of previous crops, prepare the substrate that will host future sowings and plantings.

If you share your space with chickens or Indian runner ducks, now is the perfect time to let them access the greenhouse and allow them to work on the soil. In addition to uncovering pests, the poultry will aerate the ground with their feet and naturally fertilise it.

Start by loosening and leveling the soil on the surface using a rake. Then, avoid leaving the soil bare during this period and take the opportunity to enrich it. For this, there are two options:

• use a natural mulch (straw, fallen leaves, RCW, etc.), which you will place over a layer of well-matured compost, well-decomposed manure, or another fertiliser;
• sow green manures, which will have the advantage of protecting, aerating, and nourishing the soil at the same time (for more information, we recommend the article “Green manures: why, how?”).

In regions prone to snowfall in winter, some gardeners recommend spreading a thick layer over the soil using a spade. This helps to “clean” the ground and eliminate the last remnants of crops. You may also choose to remove a portion of the topsoil (about ten centimetres) and replace it with a new supply of topsoil.

Prepare the soil in the greenhouse

Do not neglect ventilation

During the cleaning of the greenhouse, take the opportunity to thoroughly ventilate the entire structure. In autumn and winter, ventilation of the greenhouse is just as essential as in other seasons, to maintain a correct humidity level and limit the development of diseases.

Ventilate regularly, preferably in the morning during dry weather, and check that the natural vents are operational. You can also use a hygrometer, which will indicate when it is appropriate to ventilate.

Ventilate the greenhouse

Winterise the irrigation system

If you have installed a watering system in your greenhouse (automatic or not), it is also time to store it for the cold season. As most plants are in dormancy, their water needs will be significantly reduced. The watering system can remain in place in regions with mild climates, where it does not freeze or rarely does, or under heated greenhouses. Its flow rate will simply need to be adjusted. In unheated greenhouses and in other regions, we recommend winterising your watering system. First, check the equipment:

• the operational condition of the watering nozzles (which may sometimes be blocked by soil or plant debris);
• the integrity of the hoses;
• the absence of moss or algae.

Then, drain the hoses to remove any standing water and let them dry in the sun before storing them for the next season.

Prepare the plants that will spend the winter in the greenhouse.

Autumn is also the time when frost-sensitive or less hardy plants need to be sheltered for winter: citrus trees, bougainvilleas, succulents, exotic plants… Cuttings can also be stored there.

To winter your plants under good conditions, inspect them thoroughly beforehand. Check for the absence of pests (aphids, mealybugs, whiteflies, spider mites, etc.), as well as any diseased parts, which you should remove immediately. In a greenhouse, in a confined environment, the spread occurs more quickly than outdoors. You can find all our tips to naturally prevent the appearance of diseases and pests in greenhouses.

In a cold greenhouse without a heating system, you can also install additional protections around your plants to gain a few degrees: winter covers, bubble wrap, or cardboard. You can also enhance the greenhouse’s insulation with specific sheets or panels. Finally, there are various types of supplementary heating available if needed: electric heaters, heat mats, heating cables, etc.

A cleaned and prepared greenhouse for winter