How to Prepare Your Greenhouse for Winter: 7 Things to Check

Winter brings different challenges to your greenhouse. Freezing temperatures, strong winds, and shorter days all affect how well it performs, even if you're just growing a few trays or keeping herbs alive.

The month of October is a good opportunity to check the structure and make sure everything is ready before the cold arrives. Blocked drainage or a loose panel might not seem like much now, but it's better to find it on a mild afternoon than during the first frost. 

These seven recommended checks will help prepare your greenhouse for winter and keep it in good shape for spring. 

1. Inspect the Frame, Panels, and Fasteners

Start by checking your greenhouse from the outside. See if there are loose panels, missing fasteners, faulty frame sections, and gaps where the structure meets the ground. Pay attention to the roof and corners, where harsh weather can put stress on the structure. 

If you have a polycarbonate greenhouse, ensure the panels are securely and free of cracks. Clean them according to instructions so more natural light can reach your plants during winter. 

Vego's Pacific Greenhouse is built with an aluminum frame, polycarbonate panels, while specifications vary by model. Check the wind resistance and snow-load ratings of different models, and don't assume every greenhouse can withstand the same conditions.

2. Check Doors and Vents

You don't want cold drafts and wind coming through doors or loose panels. So check the door alignment, hinges, and openings where the frame meets the panels. Fix obvious gaps that let wind blow directly onto plants or allow heat loss. Don't seal up your ventilation openings though as your greenhouse still needs to release excess heat and moisture. 

Open vents and make sure they move freely and not obstructed after months of use. You should aim to keep your greenhouse protected from harsh weather while still being able to control airflow. 

3. Clean Out Old Plants

If your summer crops are done, clear out fallen fruit, dead leaves, and faded plants. Old plant debris can shelter pests and disease, and these issues can carry over into the next growing season.

Look at the undersides of leaves on plants you're keeping. Look for aphids, spider mites, diseased foliage, and other signs of trouble. Remove diseased plants promptly, and clean reusable trays and tools before storing them. If you're growing spinach, kale, herbs, or other cool-season crops, leave them be if conditions are suitable.

If you plan to reuse a greenhouse bed in winter, remove finished crops and refresh the growing area as needed. This will make it much easier to manage when winter growth slows down.

4. Clear Drainage and Areas Where Snow Can Accumulate

Water needs somewhere to go. Before winter, clear leaves and debris from gutters, drains, and the area around the greenhouse so rainwater can flow away from the structure rather than pooling at its base.

Look at the surrounding ground, too. If water regularly collects along one side of the greenhouse, consider whether the existing drainage needs improvement. Persistent wet conditions can make the area harder to work in and may cause problems around the foundation.

If snow is common where you live, check the greenhouse's rated snow load and make a plan for removing snow when necessary. Snow sliding off a roof can also pile up against sidewalls or block doors, so leave room around the structure for safe access.

5. Prepare for Winter Temperature

The temperature inside a greenhouse can change fast, even in a single day. Sunshine may warm it quickly in the afternoon, while temperatures can drop after sunset. Meanwhile, moisture from plants and soil can accumulate in conditions where ventilation is limited.

You can put a thermometer inside the greenhouse so you know how cold it actually gets overnight, and how warm it becomes during sunny days. Ventilate when the greenhouse becomes too warm or humid, even in winter. Keep plants spaced well enough for optimal airflow, and avoid overwatering. 

If you plan to grow through winter, decide on how much protection your crops will need. Some gardeners can grow hardy greens in an unheated greenhouse, while others may need row covers, suitable supplemental heating, or grow lights.

6. Decide What to Grow and Protect the Plants You Keep

Decide whether your greenhouse will keep producing in winter or simply protect your plants and equipment until spring. 

For an unheated greenhouse, cold-tolerant crops are the most ideal. Spinach, kale, Asian greens, and some herbs can remain useful in cool conditions, although growth slows as daylight decreases. Warm-season crops such as tomatoes, peppers, and basil need considerably more warmth and light. A greenhouse may extend their harvest into fall, while an unheated structure might not be able to keep them growing through winter. 

Vego's Pacific Greenhouse range is designed for season extension, with polycarbonate panel options and roof ventilation. You can also use compatible raised garden beds inside the greenhouse to keep crops organized and make soil management easier. Raised garden beds make it easier to organize crops and cover a smaller growing area rather than trying to protect all your plants. 

If you're considering supplemental heating or grow lights, think about the crops you’re growing first. Adding heat or lighting won't make up for temperatures that are too low. Choose an approach that makes sense for what you plan to grow and the conditions your greenhouse can maintain. 

7. Winterize Irrigation and Store Equipment 

If freezing temperatures are expected, water left in hoses, tubing, filters, or connectors can freeze and expand, potentially damaging your equipment. Turn off the water supply and drain any components that could hold water. Disconnect garden hoses, empty drip lines, and remove filters that might trap water. 

For gardeners using Vego Garden's Irrigation Kit as their watering system, it is recommended to thoroughly drain the components and store them indoors during freezing temperatures. 

Clean out clogged nozzles, check connectors, and make a note of anything that needs replacing before spring. If you’re planning to use your greenhouse in winter, keep essential tools somewhere dry and accessible. If you're closing it, remove anything that could be damaged by freezing or damp conditions.

What If You're Not Growing Through Winter?

Remove finished plants, check the structure, clear drainage, and store your irrigation equipment. Make sure vents and doors are secure, and the greenhouse is ready for the weather it will face.

It's still worth checking the greenhouse periodically through winter. Look for loose panels, snow accumulation, and any signs of water seeping in. You can also start planning the next growing season. Decide which beds need topping up and which crops you want to grow. 

FAQs 

When should I prepare my greenhouse for winter?

Start in fall, before freezing weather is expected. Check the structure, clean the growing area, clear drainage, and make sure vents work properly. Drain irrigation components before freezing conditions can damage them. The exact timing depends on your local climate.

Should I close all greenhouse vents in winter?

No. Close or adjust vents when temperatures fall, but open them when needed to release excess heat and humidity. A sunny winter day can still make the inside of a greenhouse surprisingly warm.

How do I keep a greenhouse warm in winter?

Start with a well-maintained structure, sound panels and seals, and a layout that makes the most of natural sunlight. You can add inner row covers or suitable insulation, and use supplemental heat where necessary. Remember that an unheated greenhouse can still fall below freezing.

Do I need to clean my greenhouse before winter?

Yes. Remove dead plants, fallen fruit, weeds, and other debris, and clean reusable trays and tools. This reduces places where pests and disease can linger and gives you a cleaner start next season.

Can I grow vegetables in an unheated greenhouse during winter?

Yes, in many climates. Spinach, kale, lettuce, Asian greens, and certain herbs are better suited to cool-season greenhouse growing than tomatoes and peppers. Their growth depends on temperature, daylight, planting date, and the amount of protection your greenhouse provides.

Should I water plants in a greenhouse during winter?

Yes, when they need it, but usually less frequently than in summer. Check the growing medium before watering because cooler temperatures and slower growth mean soil can stay wet longer. Avoid both waterlogging and letting established crops dry out completely.

Do I need to drain greenhouse irrigation lines for winter?

If freezing temperatures are expected, yes. Drain hoses, tubing, filters, valves, and other components that can hold water. Follow the specific instructions for your irrigation system, since the safest method varies by design.

Can Vego's Pacific Greenhouse be used in winter?

Vego positions the Pacific Greenhouse as a season-extension structure. Its polycarbonate panels and ventilation help create a protected growing environment, but the growing conditions still depend on climate, greenhouse size, crop choice, and whether additional heat or protection is used. Check the specifications for your particular model before planning for snow or severe weather.

What vegetables are best for a winter greenhouse?

Cold-tolerant crops such as spinach, kale, lettuce, Asian greens, and suitable herbs are good starting points. In colder regions, choose varieties that match your expected temperatures and establish them early enough to develop before the darkest part of winter.

Is it worth buying a greenhouse just to extend the growing season?

That depends on how often you'll use it and what you want to grow. A greenhouse can give you more time for seedlings, fall vegetables, and protected crops, but a well-chosen frost cover may be enough for gardeners who only need a little extra protection. Consider your climate, available space, and growing goals before investing.

Final Thoughts

Getting your greenhouse ready for winter is mostly about making sure things don’t break in the middle of winter. 

Inspect the frame and panels, get the doors working properly, clean up old plants, and decide what you'll keep growing. Then take care of the irrigation system before the first frost. Fall maintenance can protect your growing space now and save you hassle when spring comes again.