As the colder months approach, it is essential to prepare your greenhouse to protect your plants and ensure everything is in tip-top shape for the next growing season. By taking the time to clean, insulate, and prepare your greenhouse, you’ll create a stable environment that protects your plants from winter’s chill. With the right care, you can even extend your growing season and keep certain crops thriving all year long. Here is a step-by-step guide to help you winter-proof your greenhouse and keep your plants thriving through the chill.
Clean and Clear Out the Greenhouse
Before winter sets in, give your greenhouse a thorough clean to prevent pests, diseases and mould from affecting your plants:
- Remove dead plants and debris. Get rid of any old plants, weeds or debris that could harbour pests or disease.
- Wash down surfaces, including shelves, windows and frames, using warm soapy water or a mild disinfectant to eliminate mould, mildew and algae. Please remember to disconnect your rainwater pipes/water butts to avoid any detergents entering your water supply.
- Clean the glass (or polycarbonate) panels to maximise light transmission. Dust and dirt reduce the amount of sunlight your plants receive, which will already be limited during winter.
- A power washer is also a good alternative to clean glass and bases. Take care with any gravel inside the greenhouse as it can hit glass and potentially break panels.
Check for Repairs and Gaps
A well-sealed greenhouse is key to maintaining a stable temperature and keeping out draughts and pests.
- Check the structure for any broken panes, cracks, or gaps in the glazing or framework. Repair or replace damaged areas to keep the cold air out.
- Make sure doors and vents are sealing properly. Tight-fitting doors prevent cold draughts from sneaking in.
Improve Insulation
Winterising your greenhouse requires proper insulation to help maintain an even temperature.
- Attach horticultural-grade bubble wrap to the inside of the greenhouse using clips or tape. This adds an extra layer of insulation to retain heat, especially around glass panels.
- If your greenhouse has a dirt floor, consider laying down a layer of mulch, straw, or even thick cardboard to prevent heat loss through the ground.
- If you have a larger greenhouse, installing thermal screens or curtains can help trap warm air around your plants.
Prepare Heating Solutions
If you’re growing tender plants, a heating source may be necessary to maintain optimal temperatures during colder nights.
- If your greenhouse has access to electricity or gas, invest in a small greenhouse heater with a thermostat. This will help maintain consistent temperatures.
- A natural and sustainable option is placing compost bins inside the greenhouse. Compost generates heat as it breaks down, helping to keep the air warmer.
- For delicate plants, use heat mats beneath seed trays to provide warmth directly to the roots.
Improve Ventilation and Humidity Control
Even in winter, your greenhouse needs good airflow to prevent mould and fungal diseases from forming.
- Make sure roof vents and side louvres are working properly. While you’ll need to keep most of the warmth in, some ventilation is still necessary to avoid condensation buildup.
- If humidity becomes a problem, consider using a small dehumidifier or circulation fans to reduce dampness and prevent mould growth.
Organise and Plan for Winter Growing
Once your greenhouse is cleaned and insulated, it’s time to plan for winter growing and storage.
- Place winter crops (like spinach, lettuce, and kale) in the sunniest spots, ensuring they receive the most daylight.
- Group delicate plants, like citrus trees and geraniums, in the warmest areas of the greenhouse, often near heaters or insulated walls.
- If you want to extend your growing season or ensure adequate light for winter crops, consider installing LED grow lights to supplement the reduced daylight.
Monitor Temperature and Humidity
Keeping an eye on the climate inside your greenhouse is key to a successful winter.
- Place a max-min thermometer inside the greenhouse to monitor the temperature range. This will help you adjust heating, ventilation, and insulation as needed.
- Install a hygrometer to track moisture levels. Aim to maintain humidity levels around 50-70% to avoid condensation and plant diseases.
Mulch Plants
Adding a layer of mulch around the base of plants helps insulate their roots and prevents the soil from freezing. Straw, wood chips or leaf mulch works well.
