As winter approaches, gardeners across the UK are turning their attention to one crucial task: preparing their greenhouses for the cold months ahead. Winterising your greenhouse isn't just about keeping plants alive - it's about creating an environment where growth can continue throughout the season.
Why Winter Preparation Matters
Cold weather can seriously damage or even kill many greenhouse plants, but with proper preparation, you can stabilise temperatures, reduce frost risk, and keep heating costs manageable. A well-prepared greenhouse holds heat more effectively and protects against expensive structural problems like cracked glazing or frozen plumbing.
Gardening expert Calum Maddock at HomeHow.co.uk emphasises that winterising also protects the greenhouse structure itself. "Frost, snow, wind, and ice can weaken glazing, vents, doors, and framework over time," he explains. "With the right precautions, you can extend your growing season - harvesting crops later into autumn and starting new seedlings earlier in spring."
When to Begin Winter Preparations
Timing is absolutely crucial for successful greenhouse winterising. Aim to begin four to six weeks before your first expected frost. Starting too late can leave plants and greenhouse structures exposed to sudden temperature drops.
Early tasks such as removing tender plants, cleaning debris, and inspecting the structure can be completed ahead of schedule. Jobs that relate directly to cold protection - including insulation, heating checks, and sealing gaps - should be tackled closer to the frost date for maximum effectiveness.
The Complete 8-Step Winterising Guide
Follow this expert-approved guide to ensure your greenhouse remains productive and protected throughout winter.
Clear out the space completely: Begin by removing dead plants, spent annuals, and general clutter. Old foliage can harbour pests and disease, so thorough clearing is essential. Move tender perennials indoors and harvest any remaining crops before cleaning benches, shelves, and floors.
Conduct a deep clean: Once emptied, give the greenhouse a thorough clean. Sweep out debris, disinfect benches, and scrub glazing, vents, doors, and frames using a mild cleaner or diluted bleach. Ensure drains are clear and sanitise any tools that will remain inside over winter to prevent pests and diseases from overwintering.
Check the structure carefully: Inspect glazing for cracks or clouding, replacing any damaged panels. Look for gaps, rot, or cracked seals in the framing and recaulk if required. Test doors and vents to ensure smooth operation and tighten or lubricate fittings where necessary. Don't forget to check the foundation for gaps or sinking areas.
Add proper insulation: Insulation is essential for maintaining stable temperatures. Bubble polythene remains a popular choice because it allows light through while helping retain heat. Consider foam boards or rigid panels around the base to keep roots warmer, and add row covers or thermal blankets for extra protection.
Protect water systems from freezing: Frozen pipes can be costly to repair. Turn off the main water supply and drain lines thoroughly. Wrap outdoor fixtures in foam insulation and insulate the tops of in-ground hydrants. Remember to disconnect hoses and store them inside, and protect irrigation lines, pumps, and filters from freeze-related damage.
Maintain air circulation: Good airflow prevents mould, mildew, and condensation. Use greenhouse circulation fans on a low setting and keep vents slightly open whenever temperatures allow. Avoid overcrowding plants and space them out for better airflow, monitoring humidity levels regularly.
Prepare heating systems in advance: If you use heaters, ensure they're in good working order before cold weather arrives. Service gas, propane, or electric heaters and check for faults. Seal draughts around the greenhouse while ensuring proper ventilation to prevent dangerous gas build-up.
Add appropriate winter crops and plants: Once your greenhouse is fully prepared, bring in your overwintering plants. Choose hardy varieties such as kale, carrots, parsley, and lettuce. Move frost-tender potted plants inside and shelter vulnerable perennials, monitoring for signs of frost damage throughout the season.
Essential Winter Greenhouse Products
For those seeking reliable products, several options stand out for winter greenhouse care. The Vitax Greenhouse Disinfectant with added orange oils effectively cleans pots, staging, and glass surfaces. For insulation, the Elixir Gardens triple laminated 10mm greenhouse bubble insulation offers UV-resistant protection that lasts multiple seasons.
Heating solutions like the Apollo 300w paraffin heater can prevent frost damage by heating continually for up to seven days on a single tank. For propagation needs, the Muddy Hands extra large high dome propagator provides excellent protection when heating the entire greenhouse isn't practical.
With careful preparation and these expert tips, your greenhouse can become a thriving winter haven for plants, extending your gardening season and ensuring your green space remains productive throughout the coldest months.
