Outside of winterized greenhouse close up.

Winterizing Your Greenhouse with Eric Brandstad (Forever Flowering Greenhouses)

Greenhouses are designed to work all year ’round. What is the best way to prepare your greenhouse for the winter months? Eric Brandstad from Forever Flowering Greenhouses has the knowledge and he shares it with you!

Hi, my name is Eric Brandstad with Forever Flowering Greenhouses and I have a few tips on winter and summer greenhouses.

Summer and Winter Mode

We have summer mode and winter mode. This greenhouse is a little bit more flexible and set up for summer and winter mode. For summer mode we have the sides rolled up, both doors are open, I have a white ground cover and tan grow bags. If we use tan grow bags, we can reduce surface temps quite a bit, and surface temps also help encourage cooler soil temp in the summer time. If we’re trying to do a winter strategy, yeah we should use black ground cover and black grow bags and be able to switch those out when we go into the summer mode. Keeping the black ground cover on the ground and having the white to put back down and take off makes it easy to go from summer to winter mode.

Temperature Gear

Typically, the soil temperature helps regulate that plant temperature, so you can quantify that by using an infrared thermometer. So, I do this in the summer time as well, but for the winter time you can also see what the leaf surface temperature is on the plant. I’ve seen leaf surface temperatures up pretty high and soil temperatures remain low. But the minute that the heater turns off or the sun goes down, and the air temperatures go cold, the plant temp will go down just as fast. So if the soil temps are 46 degrees, the plant temp will go down to 46 degrees as well. So, maintaining good soil temps is important to go through the winter time. Using a 6 inch soil probe will tell you what your soil temperature is in a 30 gallon, 100 gallon, and even a 5 gallon grow bag. The smaller the container, the easier it is to keep warm. These bigger grow bags are a lot harder to keep warm in the winter time. If you have them up off benches, yeah you can circulate warm air underneath if you don’t have a radiant heating system. Taking and putting your grow bags in a insulation blanket of some kind will also help boost soil temps.

Avoid Cold Water

Watering with warm water will also help. You don’t want to come out with well water. It’s harder to keep the soil temps up if you’re watering with cold water.

Choose Proper Cultivars

Making sure you choose the proper cultivars is also something to pay attention to as well. Going in the winter time, some varieties are more resistant to cold and mold than others.

Pay Attention to Humidity

In the winter time, humidity can be a problem in the greenhouse, typically because it’s humid outside, it can be raining. When you heat the air, it has more capacity for holding moisture and when you don’t have a radiant heating system and your soil temps are remaining cold, the plants will respirate and try to use that water to keep from freezing up. So, we deal with a lot more humidity in the winter time and the best defense is actually to use less water, smaller containers at times, and to also make sure we have a radiant heating system. The cooler air helps us fight pathogens and keeps the pests down. We also want to keep fresh air going through the greenhouses and so that way can be through mechanical ventilation, using the exhaust fans and intakes, or passive ventilation, rolling up the sides. Mechanical ventilation is much easier in the winter time to exchange the air, to keep water from coming inside the greenhouse. We don’t have to do it as much. I prefer passive ventilation for summer mode and mechanical ventilation for winter mode.

Snow Loads, Mechanical and Passive Ventilation

Also, making sure that the greenhouse can close up. Some of the greenhouses I deal with for winterizing would be being able to close it up and have proper heating systems to reduce snow loads. These hoop houses have a tough time shedding snow because of a flat spot on the roof. So in order to reduce snow loads, you want to make sure that you have ample air temperatures in the greenhouse. If you don’t have ample air temps in the greenhouse, you might want to take the cover off for the winter time and just let it snow and the wind blow through, because the rigid frames will hold up in the winter time without the skin. A lot of people don’t use their greenhouses in the winter time, even though that’s when they’re intended for. So, if you’re not using your greenhouse in the winter time, you don’t need to heat it, you can just take the cover off. If you’re keeping your greenhouse skin on and you’re not using your greenhouse, you’ve still got to keep it warm to reduce that snow if you’re in the snow country. Other greenhouses that might have higher snow loads, gothic frames and A frames are a different story. But when we’re talking about these hoop houses, and using them only for the summer time, it’s best to take the skin off, protect them that way.

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