READY TO GROW: With a little preparation you could be growing all winter long (Image: Getty)

Winterising your greenhouse is one of the most important steps you can take to help your plants survive the cold months ahead. A well-prepared greenhouse holds heat more effectively, protects plants from frost damage, and prevents expensive problems like cracked glazing or frozen plumbing.

Cold weather can seriously damage or even kill many greenhouse plants. By winter-proofing your space, you can stabilise temperatures, reduce the risk of frost injury, and keep your heating costs down thanks to improved heat retention.

Winterising also protects the structure itself. Frost, snow, wind, and ice can weaken glazing, vents, doors, and framework over time. With the right precautions in place, you can extend your growing season — harvesting crops later into autumn and starting new seedlings earlier in spring.

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Timing is crucial. 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 — such as insulation, heating checks, and sealing gaps — should be tackled closer to the frost date.

Gardening expert Calum Maddock at HomeHow.co.uk explains why winterising is essential. Here’s his eight-step guide to preparing your greenhouse for winter’s onslaught.

How to winterise: The key steps

Clear out the space: Remove dead plants, spent annuals, and general clutter. Old foliage can harbour pests and disease, so it’s best to clear it all away. Move tender perennials indoors and harvest anything still growing. Clean benches, shelves, and floors so the space is fully ready for winter prep.

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. Rinse well and treat any algae or moss if needed. Make sure drains are clear and sanitise any tools that will stay inside over winter. This prevents pests and diseases from overwintering.

Check the structure: Inspect glazing for cracks or clouding. Replace 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. Check the foundation for gaps or sinking areas and repair any structural weaknesses.

Add insulation: Insulation is essential for keeping temperatures stable. Bubble polythene is a popular choice because it allows light through while helping the greenhouse retain heat. Foam boards or rigid panels around the base keep roots warmer. Add row covers or thermal blankets for extra protection and consider mulching the floor with straw or leaves to prevent ground frost.

Protect water systems: 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. Disconnect hoses and store them inside. Drain and protect irrigation lines, pumps, and filters to avoid 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. Monitor humidity levels and increase ventilation if moisture builds up.

Prepare heating systems: If you use heaters, ensure they’re in good working order before the cold weather sets in. Service gas, propane, or electric heaters and check for faults. Seal draughts around the greenhouse while ensuring proper ventilation to prevent gas build-up. A well-prepared heating system will keep plants comfortably warm during freezing spells.

Add winter crops and plants: Once the greenhouse is ready, 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. Monitor watering needs, signs of frost damage, and pests throughout the season, and use heaters or thermal blankets if temperatures drop too low.

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