During the 2022 season we completed the final touches to our One-Story Greenhouse. Because it took longer to finish than anticipated, we won’t be able to talk about starting Fall seedlings for the garden 🙁. An additional feature under consideration is a solar heater. We’ll see.
To compliment the greenhouse we are building three cold frames which should be ready by spring 2023. These will allow us to harden-off seedlings produced in the greenhouse. The cf can also be used to extend the fall season for spinach, lettuce, kale, etc. There’s nothing better than fresh greens when little else is going on in the garden!
The design of the cold frame (cf) is simple and made of plywood and topped off with an old window purchased at Habitat for Humanity. Cement pavers serve as the cf’s foundation to preserve the integrity of the plywood, reduce weed growth, and act as collectors of radiant energy.
The plywood’s exterior surface is painted with two coats of water soluble exterior black paint to help preserve the wood and perhaps absorb a little heat. The windows are sanded, glazed and painted with two coats of latex exterior white paint (both sides) and attached to the cf with two door hinges. The interior plywood walls are also painted with two coats of latex exterior white paint to preserve the wood structure and reflect light within the cold frame.
If you’ve never used a cold frame please be aware that they can turn into ovens when the sunlight pours through the glass. Let’s just say that I’ve burned up a few plants over the years. Even with temps in the 50F’s, a closed up cold frame can fry your plants! Simply prop open the window, in the morning, and all should be well. You may want to place a thermometer in the cf so that you can monitor its internal temp.
Although we’ve elected to publish this post prematurely, we promise to provide updates, measurements, pics, etc.
As many gardeners already know, there are a myriad of cold frame and mini greenhouse designs available online. Recently, our co-author (John L. Dose) wrote a piece on a similar topic, DIY Greenhouse and Cold Frame. My spin on this theme will examine my recent experience with a decent mini-greenhouse purchased on-line from Quictent.
The overall design of this structure is pretty good, however, a few improvements are in order. Once the panels are zippered shut, there is no possibility of cross ventilation. In the early spring, in Zone 6, this can prove fatal to young seedlings. The enclosed structure does an excellent job of staying warm but can get pretty hot on a 50 – 60 F degree day with good sunlight. If the grower isn’t close by to vent the front panels, he or she runs the risk of damaging young seedlings. To remedy this I’m going to insert two side vents. The other concern deals with securing the structure to the ground. Tent spikes are not provided to achieve this end. Thus, a trip to a local vendor needs to be done before setting sail (literally).
Overall, I do recommend this particular growing structure as it goes up easy and is easily packed away between uses. It also serves to harden off seedlings when transitioning plants from the greenhouse to the field. In a manner of speaking, the mini-greenhouse (MG) design serves a similar function as a cold frame. Next season, 2023, we plan to build 3 cold frames (CF) and perhaps place the MG on top of a raised bed. this will allow us to evaluate which system does the best job.
Hi! Johnny L. Dose here with another contribution to The Garden Dreamer.
Just a few words on two basic building materials needed for homemade cold frames and greenhouses: polycarbonate panels and wood.
Polycarbonate panels: (www.farmtek.com) sells the panels shown below in 4’ x 8’ sheets and larger. These panels are double walled. The double wall creates a micro greenhouse effect inside the panel, which helps to retain heat. They are also transparent, UV resistant, and will last much longer than polyethylene sheeting. Unfortunately, the cost of shipping is not free. So, you should consider including your friends or your gardening club on the order. These panels are light in weight; therefore, the increased volume of the order does not increase the freight cost by much…I think.
Wood: Since 2 x 4’s are expensive, at the moment, consider businesses that are throwing away pallets and ask if you can have them. HVAC companies, as well as places that sell riding lawn mowers, often have crates that can be re-purposed for a greenhouse or a cold frame. Clearly, you will need to find an easy way of pulling the pallets apart. For this not so easy task, you can try either an isolation tool (multi-tool) or a stepped pickle fork that can be used with an air-hammer. At least, these two options I’m going to test out once my pickle fork kit arrives next week from Amazon.
I’m planning to use a canopy frame (10’ x 20’), EZ-up, or similar to make a greenhouse using the material described above. I will use a combination of cable ties, deck screws, and duct tape to hold it all together. This approach will be easy to take apart, should a building inspector show up, i.e., this greenhouse does not count as a permanent structure to the property. The important thing is to secure whatever you do with a canopy against strong winds. So, tie it down like Lilliputian or it will take off like a big kite. The cat mocks me now as I type. What does he know?
Anyway, feel free to ask me any questions about my experiences with two basic building materials needed for homemade cold frames and greenhouses. I’ll stop now and save some material (pun intended) for my next post as well as gather some data to report back.
You are probably asking yourself, “aren’t all greenhouses one-story structures”? Well, for all practical purposes, yes, they are. While chatting with a new acquaintance at Three Story Coffee, I jokingly suggested that I would name the St. Joseph Street Community Garden greenhouse, the One-Story Greenhouse. Anyway, and although not too funny nor smart, the name stuck.
Our main reason to build a small (60 ft2) passive greenhouse is to grow seedlings on a schedule best suited for a timely planting. Because the greenhouse is passive and won’t have electric or gas-powered heating or cooling capabilities, it’s primary use will be during early to late-Spring and Fall months. My previous greenhouse was utilized in this same manner, and it worked quite well. Here in Central Missouri, our weather is often pleasantly mild during Spring and Fall seasons.
We are happy to announce that the One-Story Greenhouse was completed on May 6, 2022. We had originally envisioned building a wood structure fitted with old windows, however, the price for these materials continued to rise. This caused us to look for a DIY kit greenhouse. After a fairly in-depth search we opted to purchase a 6 ft x 10 ft passive structure.
Although one of the side walls faces the south, the full intensity of oncoming sunlight is filtered by a few oak limbs which sway far above the structure. It’s actually ideal since the partial shade doesn’t permit the greenhouse to become overheated.
The next step involves building shelves and and a potting area. I’ll update this post once we have accomplished this.