Winterizing a greenhouse involves several steps, including deep cleaning, decluttering, considering heating and lighting, insulating the structure, adding plants that need protection, and making a care list for all plants. Plants are affected by cold in several ways, such as freezing their cells, causing damage to nutrient and water pathways, and affecting their growth. To prepare your greenhouse for winter, follow these steps:
- Clean the structure thoroughly, ensuring it is spick and span.
- Declutter the space and airflow to ensure plant health.
- Consider heating and lighting solutions for shorter days and colder nights.
- Insulate the greenhouse and water outlets, and add plants that need protection.
- Make a care list for all plants and their winter needs.
- Insulate the greenhouse with bubblewrap and cloches to protect plants from frost and maintain optimal temperatures.
Growers should ensure they have the proper cladding for their climate and add insulation if needed. This can include materials like heat retention curtains, thermal insulation foil, or bubble wrap.
To overwinter an unheated greenhouse, declutter, thoroughly clean, and then insulate with bubblewrap and cloches.
Inspect all areas susceptible to air leakages, structural damage, condensation buildup, and plant pests. Make it a priority to open the door during the warmest part of the day on days above 40°F. You can also help heat retention by lining the outside and inside of the lower wall with additional straw, bricks, rock, or 4×4 lumber.
Clean your greenhouse by removing everything and giving it a good scrubbing. Don’t forget to wash any pots before starting any winterizing tasks.
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How to heat a greenhouse in winter for free?
To heat up a greenhouse, create a “hot bed” or composting pile filled with wood chips, mulch, manure, vegetable scraps, hay, and vines. This can generate up to 100 degrees Fahrenheit and can be used as a planting area. To absorb heat during sunny days, add black water tanks in the greenhouse, stacking them in direct sunlight or facing north. Use 2. 5 to 5 gallons of water per sqft.
Build a greenhouse with double layers for more insulation, such as twin wall polycarbonate greenhouses like the Riga. These greenhouses provide great insulation for all four seasons, especially in high elevations and cold weather. This method can be an effective way to increase the temperature inside the greenhouse.
How can I heat my greenhouse for free in winter?
To heat up a greenhouse, create a “hot bed” or composting pile filled with wood chips, mulch, manure, vegetable scraps, hay, and vines. This can generate up to 100 degrees Fahrenheit and can be used as a planting area. To absorb heat during sunny days, add black water tanks in the greenhouse, stacking them in direct sunlight or facing north. Use 2. 5 to 5 gallons of water per sqft.
Build a greenhouse with double layers for more insulation, such as twin wall polycarbonate greenhouses like the Riga. These greenhouses provide great insulation for all four seasons, especially in high elevations and cold weather. This method can be an effective way to increase the temperature inside the greenhouse.
What temperature is too cold for a greenhouse?
To maintain optimal plant growth, keep your greenhouse temperature below 3C (37F). Tender plants like pelargoniums, half-hardy fuchsias, and citrus trees prefer a minimum of 7C (45F), and safest at 10C (50F). This temperature is ideal for young plants and plug plants. If you have a conservatory, use it to overwinter delicate plants. Position heaters carefully, placing them in an open, central spot away from water and angling the heater to prevent foliage desiccation by direct airflow above nearby plants.
Do you need to harden off plants from unheated greenhouse?
Proper hardening off of plants involves thickening cell walls and leaf structures, focusing more energy on root development and reducing excess water, making them stronger, more rigid, and less susceptible to freeze damage. This slower growth creates a firmer plant that can handle the stresses of outdoor conditions. If not hardened off, wind, sun, or cold can lead to significant wilting, browning leaf edges, or even death.
Hardening off is a time-intensive process, ideally done over two weeks, but it is more sensitive than bringing well-rooted, mature plants from a greenhouse and acclimating them to the new environment. For less cold-sensitive crops, hardening off occurs throughout early spring, while for more frost-tender crops, it is done until the risk of frost is unlikely.
For extra safety at home, the general rule is to wait until temperatures consistently fall in the low 50’s. In some areas, it is done after Mother’s Day, but with warming temperatures, it is rarely necessary to wait that late to be safe from hard frosts.
How cold is too cold for seedlings in a greenhouse?
To slow down crop growth in a market, reducing the temperature is the best way to do so. Most crops can tolerate an average temperature of 50° F, with cold-tolerant crops handling temperatures of 35 to 40° F. Cold-sensitive crops, like basil, should not be held below 55° F. When temperatures are significantly reduced, plants need less water but still need some water. Low temperatures don’t need as much light, but crop quality can be reduced if given too much shade.
Increasing humidity decreases the amount of moisture that air holds, making it more difficult for plants to dry out and leaves stay wet longer. This can also inhibit rooting, which can be problematic during propagation and transplanting. Therefore, humidity and moisture management become more important when greenhouse temperature is reduced.
Freezing or chilling injury occurs when plants are exposed to temperatures below freezing, which is not suitable for many cold-sensitive plants, including those native to tropical areas. Chilling injury can occur at temperatures above freezing and as high as 54° F. The potential of freezing and chilling damage increases with the duration of low temperature exposure and the magnitude of the temperature decrease.
How do I prepare my greenhouse for winter?
To prepare a greenhouse for winter, follow these five tips:
Thoroughly clean your greenhouse: Remove all plants and clean the area thoroughly. Wash benches and surfaces, empty pots, and scrub equipment with disinfectant to keep pests away.
Prepare soil in garden beds: Prepare soil in garden beds, fix holes and oil hinges, prepare your heating system, and create healthy airflow.
Fix holes and oil hinges: Fix holes and oil hinges, prepare your heating system, and create healthy airflow.
Prepare your heating system: Prepare your heating system, create healthy airflow, and ensure your heating system is functioning properly.
Create healthy airflow: Create healthy airflow in your greenhouse to help your crops stay in the best shape during the harsh winter conditions.
Will an unheated greenhouse keep plants from freezing?
A greenhouse can help prevent plants from freezing by acting as a protective layer, trapping heat and creating a warmer microclimate than the outside world. However, it is not an impenetrable fortress against extreme cold. A standard cold greenhouse only offers a temperature bump of about 2ºC if the mercury outside plummets well below freezing. If the greenhouse is too cold and plants are still affected, using a heater can help raise the temperature further. In the world of frost protection, every degree counts.
Will plants freeze in a unheated greenhouse?
A greenhouse acts as a protective layer, trapping heat and creating a warmer microclimate than the outside world. However, it’s not an impenetrable fortress against extreme cold. A standard cold greenhouse only offers a temperature bump of about 2ºC when the mercury outside plummets below freezing. If your greenhouse is too cold and your plants are still affected, you can raise the temperature further by using a heater. Greenhouse Emporium offers strategies to keep your greenery thriving even when the snow starts to fall, such as using a heater to keep plants warm.
How do I protect my greenhouse in the winter?
Horticultural bubble wrap and fleece are designed to insulate greenhouse interior walls, block drafts, and protect plant roots from cold temperatures while allowing light in. It is recommended that transparent insulating materials be sourced from local garden centers.
Can you leave plants in the greenhouse over winter?
Winter gardening can be done using a greenhouse, with minimal alterations needed. The main concern is raising the inside temperature to above freezing and allowing daytime ventilation to maintain plant oxygenation. This task is not difficult or expensive, and can be decided on by the individual. Some greenhouses work best in winter, but single-walled ones, especially those made of soft PVC sheets, should be avoided.
A pitched or rounded roof is recommended to allow snow to be easily removed or slide off. Some greenhouses can grow down to 0 degrees, but it’s not a difficult or expensive task. Ultimately, the choice of greenhouse depends on the desired growth conditions and budget.
How do you overwinter a greenhouse?
Overwintering an unheated greenhouse involves decluttering, cleaning thoroughly, and insulating with bubblewrap and cloches. These steps prepare the greenhouse for spring and help tender perennials survive winter weather. No, a greenhouse doesn’t need to be heated during winter. Placement in a sunny position and proper insulation with sheets or bubble wrap can significantly improve the greenhouse’s temperature. Design expertise is also provided in your inbox, including inspiring decorating ideas, practical gardening advice, and shopping round-ups.
📹 How Our Winter Garden Survived -23°F (-31°C) With No Heat
Please join me for an update on our winter garden after a week of subzero temperatures and a low of -23°F (-31°C). If you shop on …
I’ve done square hoop-houses, but I have run the tubing from opposite corners (e.g., upper left to lower right) so it makes an “X” in the middle, like a lot of camping tents. It also helps the snow to slide down the four sides, so that snow is less likely to collapse the whole kit-and-kaboodle. “Hammertime…”–I think you’ve just dated yourself, my friend! : )
That temporary cold frame is ingenious! I extend growing season by late fall plantings in a poly tunnel that has a 16 ft raised bed down its center. I then cover the raised bed inside the poly tunnel with several mini greenhouse frames joined together down the entire 16ft length and assemble their covers overlapping them. This create a “polytunnel within a polytunnel”. I have yukon gold potatoes planted down each side of 16ft greenhouse sandwiched between bottom/top straw layer then covered with soil. I expect potatoes early January – the plan is fresh garden potatoes year round here in US Z7. Up the center between the two potato rows I’ve planted kale transplants for fresh green smoothies each morning. I also then lay black rubber mats down each side of the raised bed to soak up solar warmth during the day and release down into the soil and into the greenhouse adding some warmth. At night I pull a dble layer of Agribon frost fabric as a blanket over the top of the mini greenhouse. This year I may actually use a blanket cut in half.
Here in Nova Scotia, Canada my goal has been to have spinach in the spring as early as possible. I plant spinach in September to get it well established, eat it as baby and then use the hoops and row covers when temps get colder to keep it growing. In end of November when daily temps are 4 degrees, I cover with plastic. The spinach is protected “on hold” until early spring when I water, fertilize, prune and encourage it to continue growing getting many pickings.
Yes, I agree that you are a superb teacher Ben. I started gardening on a very reduced budget, and never yet had the privilege to own my own greenhouse – these mini polytunnel ideas are great!. I have an amazing friend that knocked up a cold frame for me from spare timber and polycarb sheeting – which is much lighter than glass and so makes the cold frame easier to move, but has to be weighted with a stone so the wind doesn’t lift the lid off. I’m just wondering if I could use an old swing frame to make a temporary green house… it will take a lot of strong plastic sheeting I suspect!
Hi Ben Great article thank you. I use the water pipe on my allotment and it works really well. You can also use pipe saddles and pipe clips of various sorts to anchor the pipe on to boards and I use pipe clips to hold my netting in place over the hoop. If you get the right ones, you can then then slide the clips up the hoops to give you access to your produce, which is very useful for harvesting. You wouldn’t want to put the pipe clips onto polythene though as it would probably make a hole. Scaffold netting is quite cheap and effective for keeping butterflies off.
That was an interesting and informative article. Thanks for posting. Over the many years I’ve been gardening in raised beds, I think I’ve tried every way know to man (slight exaggeration) to either extend or get an early start on my growing season. The biggest problem I’ve encountered is overheating my plants. Inevitably something happens too frequently where I either forget to increase ventilation on sunny days or events conspire against my doing that. So now I rely on automatic ventilation. I no longer bother using covers to extend my growing season. For me, it’s not worth the effort. However, I use temporary, removable covers on select beds very early in the spring. These serve several useful purposes. First is to thaw and condition the soil much earlier than usual. In addition, I can move many of my seedlings from indoors to my covered beds to get them conditioned for planting in the garden. And obviously, I can get an extra early start on all my veggies.
Great ideas!!! I will be overwintering some shrub cuttings(in pots), and plan to bury part of each pot in the ground to help insulate them, and use the first method that you demonstrated. I plan on using 6- 8x8x8 half block. The blocks will act as a weight to keep the plastic sheeting in place, and I will be using the stakes, and plastic coil as support for the plastic. Contemplating using the plastic on the ground as well, and cutting out the plastic in the shape of the pots before they go in the ground…. not sure about that last part? Thank you for the work that you do on these articles!!!
Thanks for the information! It’s too late for me to do anything for fall now. I am in zone 4b in BC Canada, but more in a little micro climate since I’m on top of a mountain. We already have snow on the ground. Would this work in the spring to get a head start on some lettuce, spinach and kale? And also to acclimate any seedlings? I usually can’t plant until The end of May but we’ve had snow into June before.
Absolutely love your articles. I’ve got an old shower door that’s been put behind the garden shed for about a year, going to measure it up later and see if it’ll fit one of my planters in the front garden. Really looking forward to your article on rhubarb, I’ve got some growing out the front, please cover whether it needs to be covered during the winter, keep hearing conflicting views on this.
Great article! You make everything look so doable, because it totally is!! I use hoops with plastic and old windows raised bed frames on bottom. In my zone 7a garden, the hoops are not as warm as the cold frames. I can keep mustards and corn salad growing through the snow in January in the cold frames.
Love to Rosie and her Love of broccoli 😁, This is just a passing thought to deter slugs and snails, So I thought I’d run it past you and hear your thoughts. I’m thinking of raising my beds from the ground by about an inch and running trimmed brambles from blackberry, raspberry and any other thorny plant. Sought of the equivalent of a thorny moat, Laying the brambles perhaps an inch in height, ( as long as they’re already dead, or maybe even train them around), As well as an inch out away from the raised bed, Perhaps that would be a viable alternative to deter the escargot 😁?
I’ve tried using windows to make cold frames. The glass has always shattered before spring comes. When I use plastic it always gets hit by strong winds and blows off or tears. I love the idea of cold frames though. I have Elliot Colemans books. Charles Dowding also did some interesting articles on it. Still I am a failure each time I try. High winds, heavy snow fall, and zone 5.
I’m wondering how long into the winter these ideas are feasible? I am in Wisconsin which gets lots of snow and down to 30 below. I am trying this for the first time this year, we made a hoop over our raised bed to extend the season for our Swiss Chard, kale and radishes. I also have a cold frame with nothing in it right now. If I plant something in there will it even germinate in the cold weather?
I have a query- I was under the notion that perhaps you will make some holes in the small polyhouse, the one that you covered with polythene for air passage. Should I make holes in the small polyhouse or poly-pyramids designed out of polythenes? Or do I not worry about that. I was thinking making few holes could be imp for air circulation
this was a little too expensive for me, so much so I was considering just buying a prebuilt setup. But then I got an idea of just using bamboo + twine. 1. I cut two 6ft bamboo poles in half (can use various sizes depending on bed size. my bed length was 6ft) 2. stabbed them diagonally into the bed of choice making sure both sticks cross in the middle (one side of the bed, shortest side). also make sure they are firmly stabbed into the ground, the deeper the better. 3. tied those sticks together with twine 4. repeated steps 2/3 on the other side of the bed, making sure they lined up. (if want a stronger setup do this again in the centre of the bed) 5. placed a 6ft bamboo pole on top of the two constructions I made ( should just slot onto the V shape) 6. placed fleece over the top and weighted it down with various stuff in the garden. sure the bamboo will probably rot away over time but this is a nice simple setup to help get through the colder months. if it does last you can just replace the cover with netting in the future.
Hi there Is it you that runs the GrowVeg thing with the garden planner? I am thinking of subscribing to this but i have a permaculture garden and do not usually rotate – is this a problem? The main thing is I need to know what to plant and when in my area in France – so the garden planner may help me that way what do you think?
Ive used the first method and something similar to the hoops, but i just use old clothes hanger that i dont use anymore, opening them up and making a half circle then covering the planter with pieces of clear plastics taped together x’D definitely doesnt look as nice as yours but it does the job and reuses old stuff i have lying around at home!
I built two cold frames using old shower doors mounted on top of recycled timber. ( Like a raised bed but without filling in the bed itself) I currently have strawberries in one and Rocket ( Arugula) in the other. The rocket had already cropped in this to protect them from rabbits who inhabit my allotment and they self seeded.🙂
Plastic zip ties instead of reusable string with slipknot. Plastic clothes pegs instead of wooden clothes pegs. Plastic tube instead of wooden branches. You have a sizable following, so the advice you give can help eliminate (not just reduce) plastic. Not sure if you aware but plastics are killing the ecology, and apparently there is a climate crisis. Please bro xxx