Winter Greenhouse Care

In the garden

You can grow year-round in your greenhouse

Owning a greenhouse in the Midwest comes with a little bit of extra care in the winter.

We just had our first major winter storm which dropped about 18 inches of snow in 48 hours. While the snow has lovely insulating properties for the outdoor garden, it’s important to keep heavy snow off the top of the greenhouse roof to keep it from collapsing.

Our greenhouse, the Palram Glory kit, states a max snow load of 20.5 lbs per square foot. We’re not exactly keen on testing the max limit, so during times when we get more than 3 inches of snow, we make sure to get outside with a shop broom and brush the snow off. It’s great winter exercise.

brushing snow off winter greenhouse

Cleaning greenhouse roof snow

For this winter greenhouse care task you’ll need a tall person and a good amount of space around the perimeter of the greenhouse to step and brush snow. We hadn’t really considered this when we built the greenhouse, so we’re stepping on one of our garden beds while doing this. Luckily the ground is mostly frozen and we don’t have anything precious like garlic planted there.

An unheated but monitored greenhouse

We do have crops growing inside the greenhouse, but without supplemental heat. There are a few tricks to harvesting year-round, and one of them involves monitoring the weather and temperature to know when things have thawed out.

My garden version of a baby monitor is this wonderful little bluetooth thermometer from Govee Home. It was cheap on Amazon and has worked like a charm all winter.

bluetooth thermometer sitting on potting bench

Using a greenhouse thermometer

After downloading the Govee app, you can check the real-time temperature in the greenhouse with bluetooth. The app also tracks and saves data history for two years, which can be a really powerful learning tool for successful winter growing.

The data I’ve been able to collect from this app has allowed me to see some patterns, and I now know a whole bunch more about what to expect next winter.

Sun is everything in a greenhouse

It will absolutely be warmest in our greenhouse on a sunny day between 11am-1pm. When it’s sunny outside during this window of time, the greenhouse is regularly 30 degrees warmer than the outside temperature. If it’s not sunny outside, it will only be about 3 to 10 degrees warmer. All of this to say, sunlight is everything!

If I want to try and harvest from the greenhouse when it’s below freezing outside, I’ll wait for a sunny day around lunchtime and pop in to grab some greens towards the end of the warmest window. This gives any frozen greens some extra time to thaw out. So far we’ve been able to harvest lettuce, chard, kale, spinach, dill, cilantro and parsley… all winter.

red and green lettuces overwintering

Using row covers in a greenhouse

My next experiment will be to place an additional thermometer under the row covers that are covering all the crops in the greenhouse. Many experienced winter growers have noted an additional layer of warmth underneath the covers and I’d be so curious to see the difference.

Please let me know what you think!
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