Wrap it up like a big present. In plastic. That’s how to keep a greenhouse warm in winter. Luckily, our greenhouse is small so this gift wrapping is not a giant undertaking. And it might not be the right solution for any big greenhouse owners, but for us, and our 4’x6′ growing station, this method of winterization has proved itself most competent. Like a champion, it weathered our second blast of single-digit-polar vortex temperatures in early February, it withstood wind gusts of 35 mph, and it embraced this week’s big snowstorm of 6.5″ inches all while maintaining an even 70-80 degree temperature range indoors. We can officially say, with confidence, that this is an ideal solution for any small greenhouse gardeners who live in a cold weather climate and struggle to keep plants warm throughout the winter.
We got a little behind in our greenhouse diaries updates, but by no means was February an uneventful month around here. As we all know, nature waits for no one. What was exciting twenty days ago in the greenhouse has now been replaced by exciting things happening at this very moment, so this post is a catch-up, a recap, and a new surprise all rolled into one in an effort not to make it a million miles long.
Here’s a brief recap on the winterization efforts. Essentially, in less than half a day, we built a wooden exoskeleton around the shoulder and roofline of the greenhouse and then wrapped the greenhouse in one giant piece of plastic. The plastic was stapled to the wooden skeleton which was screwed together but not screwed into the greenhouse. Instead, the wood frame rests on top of the greenhouse, secured by gravity from the wooden connection at the peak of the roof.
A 5′ foot wide roll-up curtain panel was made for the door using a curtain rod at the base and more plastic sheeting. Four bungee cords hold the plastic in place along each wall and two butterfly clamps hold the rolled-up panel in place when going in and out of the greenhouse. All it took material-wise was one roll of the plastic sheeting, six pieces of lumber, a curtain rod, a handful of screws, four bungee cords, and two butterfly clamps. If anyone would like a detailed drawing on how to replicate this plastic wrap for your own greenhouse, please send us a message or comment below and we’ll be happy to lay out the steps and materials.
Most days we leave the door panel rolled up to let a little outside air seep in through the draft in the doorframe. Just before dusk, it all gets buttoned back up again. Once winter is over, we will be able to easily remove, wrap up and save this plastic/wood frame system for the cold months later in the year. Using this type of winterization method and our one electric heater has kept the greenhouse a full 50-60 degrees warmer inside than the outside temperature. So on a 25-degree night, it will stay a consistent 75 degrees in the greenhouse. Some days, when the sun is out, the plastic keeps everything so warm we can turn the heater off completely. Both the established plants and the seedlings have really thrived in this much more consistent environment.
The only downside to this method of winterizing is that all the ventilation holes, the roof window, and each side wall from the pea gravel floor to the peaked roof get completely covered with plastic so there isn’t as much free air flow or circulation happening, and the view is reduced to a gauzy, opaque landscape once inside. The trapped heat is great for keeping everything inside warm but also invites pests to come and enjoy the tropical heat.
Over the course of February, we did see an outbreak of aphids, whiteflies, and spider mites, but a simple spray of homemade garlic water and store-bought organic neem oil did the trick to clear those up quickly.
One note on the Neem oil though – it does get rid of everything. We had some mushrooms that popped up in the pepper plants in January and also two resident spiders who were helping reduce the unwanted bug population, but unfortunately, mushroom nor spider survived the neem spray. So keep that in mind if you have some critters that you’d like to keep around.
Over the course of the month, we said goodbye and hello to a few plants. The broccoli, the pincushions, and our beautiful nasturtiums all completed their natural life cycle. As much as I hated to see these three go, at least they were moving on to the compost pile for nutrient recycling. Like our sourdough starter recipe published last week, all these first-year greenhouse plants have been the best springboards – the ones that taught us so much about how to begin in the first place. Before their final send-off, I picked the last of the nasturtiums for a bouquet. It was a big colorful cheers and thank you to my most loved flower this season…
On the hello side, we said welcome to a bevy of new seedlings as they sprouted up this month. Snapdragons, foxglove, basil, black-eyed Susan vine, cucamelons, bell peppers, spicy peppers, cosmos, dill…
We harvested the orange bell pepper for a stuffed pepper recipe, the first round of collard greens for a sausage, potato, and collard hash, and the arugula for more salads than we can count. The chives, lavender, and tarragon all got haircuts and the Santaka grew five finger-long peppers.
The geraniums are filling out so much they have completely taken over one corner of the greenhouse. Their resilience from frost recovery is pretty remarkable. I can see now why these plants have a shelf-life of 50 years if paid just a little bit of attention. With the colorful nasturtiums gone, they have been such a vibrant choice for the wintertime greenhouse.
After the bell pepper was harvested and after the spider mites came to visit, I did some trimming of the older pepper plant leaves, and pretty much overnight three jalapenos grew. Now each of the three pepper plants are blooming again, Maybe we’ll be lucky and get two summer cycles out of each plant.
This week, the most exuberant grower in the greenhouse has been the mint. At 12″ inches in height now, it’s been the epitome of spring-is-right-around-the-corner joy.
Nineteen days to go. That’s how close the first day of spring is. In anticipation, another round of seed starting begins this week. On the list for March starts are cucumbers, marigolds, squash, tomatoes, okra, collards, sunflowers, cauliflower, brussels sprouts, peas, broccoli, and zinnia. To keep things interesting, Mother Nature also might be sending two to four more inches of snow our way this weekend, just as the daffodils are popping up in the garden beds. Like I said up top, nature waits for no one. And so we carry on. Snow showers and spring flowers aside, this is the perfect time to get the summer garden started.
Cheers to almost-Spring and to figuring out the greenhouse winterization plan just as a new season approaches! Have you been starting your seeds too? If so, what are you growing this year?