11 Essential Greenhouse Tasks You Should Do Before Winter 

Greenhouses provide a safe, warm environment for seeds to start and plants to grow in. General maintenance, annual repairs, and cleaning will keep them in good shape and working order. 

Having a clean and organized space to start seeds, step up seedlings, and grow on new perennial plant splits will help foster a stable place for healthy growth, yielding in an abundant season. 

Let’s examine 11 essential fall greenhouse tasks you should do before winter to keep your greenhouses high-functioning and help you continue to have successful and enjoyable seasons.

Clean All Seed-Starting Supplies 

Fall greenhouse sanitation is a crucial task because it’s the environment where all, or most, of your garden’s life will begin next spring. Fungal pathogens like Fusarium and Phythium can survive on garden surfaces and will be ready to strike next season if you allow them to hang out in the greenhouse all winter. 

Healthy seedlings will produce healthy plants, so do everything you can to give them a good start and a fighting chance. Here are some items you should sanitize before storing them away for winter: 

Sanitize supplies and surfaces with diluted bleach, hydrogen peroxide, or ammonium chloride. Follow the instructions on your chosen product to ensure it’s safe and strong enough to kill pathogens properly. 

The University of Massachusetts Amherst UMass Extension Greenhouse Crops and Floriculture Program Disease Management Checklist is a great reference that includes disease management, humidity control, and cultural best practices. 

Toss What’s No Longer Serving You

A greenhouse can quickly become a catch-all during the growing season. I’m sure there are empty plastic containers you saved for something, several broken items needing repair, and countless random items that belong in your home, like mugs, markers, and egg cartons if you’re like me.

Get those to their rightful home to clear space for things that need to be stored inside the greenhouse for the winter, like row covers, shade cloth, and insect netting. 

Try to rehome items that aren’t serving you anymore, such as old versions of trays, random containers from nurseries, and landscape fabric no longer in use. 

Remove Organic Plant Matter

After leaving mustard greens in one of my high tunnels, I learned this lesson the hard way. The following season, we had an aphid issue on our farm for the first time because we provided them with a warm place to live and food to eat all winter.

Ridding your garden, buildings, and tools of organic plant matter, such as old greens, pruning cuttings, piles of weeds, and compost, will remove perfect places for pests and critters to hibernate. 

Deter Critters

When temperatures drop, critters like mice, rats, voles, and chipmunks seek a warm place to live for winter. Don’t allow them the opportunity to cozy up and raise their brood in your greenhouse! You’ll be disappointed if they cause damage, leave droppings, and take over your building after all the cleaning and organizing you did in the fall. 

Adopting a barn cat is always a unique, organic critter-control option! 

Sanitize And Sharpen Hand Tools 

Cleaning and disinfecting your garden tools is the perfect greenhouse task to undertake in the fall. It is crucial in ensuring their longevity and effectiveness and preventing disease from spreading. If you invest in high-quality, well-made garden tools, which many of us do, treating them well extends their life. 

Remove all debris and wash with antibacterial soap, with assistance from a brush, repurposed toothbrush, rag, or steel wool if needed. Soak rust-stained tools overnight in vinegar and scrub them clean in the morning. Then grease the hinges and tighten any loose screws. A dissolvent like Felco 980 Tool Spray will help remove hard-to-remove saps and sticky residues from pruning. 

If you know lingering disease particles are present on a particular tool, take extra steps to ensure it doesn’t harbor in the greenhouse and wreak havoc next season. Isopropyl alcohol, bleach, and boiling are a few methods to kill diseases. 

After cleaning all tools, thoroughly dry them. Then, move on to sharpening them, which you should do one to two times annually. Depending on the tools’ size and shape, use a file, whetstone, grinder, or diamond hone to sharpen them. Store them in a clean drawer, on a magnetic strip, or hang a piece of pegboard to keep them organized. 

Batten Down The Hatches

If your greenhouse has roll-up sides, windows, doors, and vents that remained open for the season, fall is the time to tackle all closing tasks. Roll them down, close them up, and install wiggle wire to secure all plastic edges. 

Greenhouses should have a ventilation system to avoid high moisture buildup and stagnant air. This system may be a simple fan that runs on a timer or an open vent. Good ventilation will keep healthy air flowing, and while it will be cold, that’s okay as long as there aren’t cold-sensitive plants inside. 

Add seasonal insulation if your setup requires it. Store things like row covers and bags that an animal could destroy inside an airtight container with a well-fitted lid.  

Make Repairs or Call For Service 

Create a list of items that need repair and complete them before you put your garden to bed. Here are some items to consider inspecting: 

If you can service anything needing repairs, do so at this time. Otherwise, call for annual service and record the appointment afterward so you have written proof of when it occurred. 

Drain Water Lines and Store Hoses 

It’s easy to forget about garden supplies like hoses, sprayers, and watering cans, but correctly caring for and storing them will extend their lives by years. Invest in a few plastic totes, drawers on wheels, or simple garage hangers, and install them on a greenhouse wall. 

Proper storage of irrigation supplies will prevent them from cracking in freezing temperatures or being chewed on by critters. 

Clean Fans, Lights, And Vents 

Create an annual maintenance schedule to make them more likely to happen. The end of the year is a great time to complete these chores so that you can focus on starting seeds when spring arrives—clean fans, vents, workstations, heat mats, soil benches, and lights. 

If any walls contain polycarbonate, spray them with soapy water and wipe them dry with a clean microfiber cloth. Vinegar-based cleaners will help prevent mold and mildew from growing inside.

A good hack for polycarbonate end walls is to connect the polycarbonate to a piece of wood rather than having direct contact with the soil. Fungus, mildew, and mold can creep up from the ground and get stuck in the polycarbonate’s tracks, making cleaning difficult. 

Ensure nothing is blocking heating mechanisms for safety purposes, and turn them on to check they’re in working order. Nothing is worse than being out of a heat source in the spring when your seedlings rely on it!

Clean Workstations 

Beginning next season with a clean and organized workstation will prepare you to hit the ground in the spring. Organize the area by taking inventory of pens, pencils, labels, soil, amendments, seed-starting supplies that need replacing, work gloves, tomato-grafting supplies, cleaning brushes, pots, trays, etc. Toss or repurpose anything broken during the season or not working well. 

Wipe down, sweep, and sanitize walls, work surfaces, and floors. If your greenhouse floors are dirt, remove all weeds and dropped seeds. Consider laying a tarp down to keep the weed pressure down. Knock down wasp nests that are no longer in use. 

Use a durable bristle brush to remove dirt and debris from your workstation. Sanitize and reseal wooden surfaces or add a non-toxic, water-based paint coat or sealant. 

Take Inventory and Stock Up

Once you’ve cleared the space of broken and unneeded items, list items you must purchase before next season. Perhaps this is a task you take on over the winter when you have time to research and find the best price.