November 9, 2026, 5:21 am | Read time: 4 minutes
To enjoy your greenhouse in the next season, it should be well-prepared for winter. myHOMEBOOK explains what owners should consider for the cold season and which mistakes to avoid.
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When should you winterize the greenhouse?
Before temperatures consistently drop below 41°F, you should prepare the greenhouse for winter. Frost-sensitive plants and vegetables, such as oleander, need special protection. The best time for this is between October and mid-November. It’s better to be early than late.
1. Start with winter cleaning
The use of the greenhouse throughout the year becomes apparent in winter. Therefore, you should first clean the greenhouse windows and clear the roof of leaves. This allows enough light to enter the greenhouse during the darker months. The garden bed also requires special attention. Remove dead plant and vegetable remains as well as weeds from the bed. Then, it’s advisable to loosen the soil a bit with your hands. The soil will also benefit from a layer of bark mulch or fleece, which protects it from freezing.
2. Perform repairs
Damage to the greenhouse may have occurred over the summer. A quick inspection can reveal its condition. To prevent cold air or pests from entering, it’s advisable to carefully check the walls, framework, and seals. The rubber seals on the doors, in particular, can become brittle over time and should be checked regularly. Small holes in the joints can be sealed with silicone.
Also interesting: Winterizing the garden step by step
3. Protect materials from frost
Throughout the season, many use the greenhouse as a storage space for fertilizers and pesticides. However, these are extremely sensitive to cold. In freezing temperatures, they can coagulate and become unusable. Additionally, the liquid in the container can expand due to the cold–in the worst case, even burst. To ensure the materials survive the winter well, it’s advisable to move them to frost-free areas. Garden tools and furniture should also be brought indoors.
4. Regular ventilation for 10 to 15 minutes
The air in a greenhouse is humid and stuffy. Proper ventilation is crucial here. To prevent mold and rot, it’s recommended to proceed as you would in your own home: regularly open the windows for 10 to 15 minutes. This ensures the plants in the greenhouse receive enough oxygen.
5. Secure night warmth with water canisters
Water tanks act like natural radiators for the plants in the greenhouse. Black canisters are ideal because they store solar heat during the day and release it at night when the water cools down.
Important: The warming effect is usually noticeable only with a 500- to 1000-liter canister.
6. Check the heating
In a heated greenhouse, the gardening season is extended a bit. This is especially beneficial for heat-loving plants. For olive or fig trees, it can be dangerous without a heater. Mediterranean potted plants lose their leaves and flowers at temperatures around freezing. Therefore, it’s important to give the heater a thorough winter check. If it no longer works, it should be repaired or replaced. Heating mats and thermometers are also good alternatives to a heating system.
7. Insulate the greenhouse
Even without heating, insulation works reliably. Instead of a heater, the greenhouse should be insulated with a film. A three-layer bubble or bubble wrap is suitable for this purpose. It should be light-permeable. The question arises whether to attach the film inside or outside. Both have advantages and disadvantages.
Outside, the film is exposed to sunlight, wind, and weather, which can cause it to deteriorate faster. If the film is attached inside, condensation may form between the greenhouse wall and the film, promoting algae growth and worsening the greenhouse climate. A gardener’s rule of thumb suggests insulating small greenhouses from the outside and large ones from the inside.