A hobby greenhouse is an addition to the garden that most gardeners dream about, but having no prior experience with greenhouses, they often don’t know where to start. My guest on this week’s encore episode, Master Gardener Sheri George, shares her many years of experience growing in greenhouses and her tips for selecting and operating a greenhouse.
Sheri began greenhouse gardening after moving to Colorado from Texas. She was struggling to garden outdoors in a high desert, so her husband got her a greenhouse kit for Christmas. The greenhouse offered her plants protection from high winds and extreme temperatures, and she could raise tomatoes and other vegetables year-round that would otherwise struggle to grow on the Colorado Plateau.
Sheri would later move to the Atlantic, Georgia, area, and that’s where I got to know her in 2011 as I filmed an episode of my PBS series “Growing a Greener World®.” She’s upgraded her space since then and has gained even more valuable knowledge and experience to share.
When I spoke with Sherri for the podcast in 2019, I did not yet own a greenhouse. I finally got my greenhouse in 2022 — after navigating permitting issues — and it’s been a dream come true as well as a learning experience. Learning the ropes is a challenge but so rewarding.
For a full recap of my conversation with Sheri, you can read the show notes from the original airing.
Why Grow in a Greenhouse
Greenhouses create a microclimate, with controlled temperature and humidity. The glass or plastic walls and roof capture the energy from the sun, creating an environment that is much warmer than the outside — during the daytime at least.
The sealed environment of a greenhouse also creates a buffer from pests and diseases that easily reach and ravage outdoor plants.
Greenhouses can become too hot for plants during the day and then become too cold at night. To operate a greenhouse year-round, gardeners must learn to manage daytime ventilation and nighttime insulation and heating. Gardening in a hobby greenhouse is a time investment that requires constantly monitoring the temperature, moisture levels and overall health of the plants you grow there.
Siting and Sizing a Greenhouse
Before erecting a hobby greenhouse it’s important to realize that it is a structure just like any other structure you may wish to erect on your property. Setbacks, size restrictions and permitting may all apply, especially if you intend to run electricity to the greenhouse. If your greenhouse is not something that can be easily moved — perhaps, like mine, it’s on a concrete slab — you want to ensure you have all of your i’s dotted and t’s crossed before setting it up.
If you live in a homeowners association, check the bylaws and covenants. A greenhouse may be prohibited.
The best spot to place a greenhouse is the sunniest spot in your yard. A greenhouse should get at least six hours daily of sun exposure in winter. Most greenhouses have a wide side and a narrower side rather than being a perfect square. Site a greenhouse so a narrower side faces east. That way, the longest stretch will have southern exposure, maximizing how much light the greenhouse receives from the sun.
If possible, position the greenhouse so it receives afternoon shade in summer. Too much summer sun will cause the greenhouse to overheat.
Once you know what you are allowed to do and where there will be adequate sunlight, the next step is to determine the appropriate size. Think ahead about what you will plant to grow in the space. If you will use the hobby greenhouse primarily to grow seedlings, a smaller space may suit you. If you plan to overwinter tropical plants, you will need more space for those mature plants and larger containers.
Most hobby greenhouse owners will recommend that whatever size you calculate you’ll need, buy a greenhouse that is one size larger — or the largest size you have the permission and means to build. This will give you room to expand your greenhouse operation even if you don’t think you’ll need all that space right away.
Sheri’s first greenhouse was 8’x12’ and her second was 13’x20’. Still, she knew it wouldn’t be long before the larger greenhouse was overflowing with plants.
An easy and economical way to build a greenhouse is with a kit. They come in an array of sizes, offering you the flexibility to find a kit that meets your restrictions and desires.
Hobby Greenhouse Must-Haves
To have a successful hobby greenhouse, there are some non-negotiables.
It’s vital to keep the air within a greenhouse moving to balance the temperature and prevent fungus and other diseases. In every greenhouse, there are inevitably pockets of hotter and cooler air. Those pockets will influence the health of your plants, but fans will keep all the air moving and eliminate the issue.
Sheri recommends a large fan mounted to the greenhouse gable. She adds two oscillating floor fans and has found that the combination serves her greenhouse well.
In addition to fans, the ventilation should include the ability to open upper panels to allow hot air to escape. Most kits include automatic ventilation devices. These are filled with wax, and as the temperatures in the greenhouse rise, the wax expands — pushing the panel open and releasing hot air. If you build your own structure, you can also buy these devices to add to your roof panels.
Temperature monitors help you keep a watch on the air temperature within a greenhouse. The best models have an alarm wirelessly connected to a second device in your home or to your smartphone. When temperatures rise or fall outside the safe range, the monitor will trigger your device to sound the alarm.
Seed Starting Trays
The greenhouse environment is ideal for starting seeds to get a jump on the garden season. You should order seed trays ahead of time so when seed starting time arrives, you’ll be ready to go.
If you plan to grow seedlings in the greenhouse, you will need heat mats. Seed starting trays sit on these warming mats to increase the soil temperature. Warm soil is key to seedling health, and even when the air dips as low as 30 degrees F, your seedlings will continue to thrive in warm soil.
If you plan to overwinter tropical plants or grow crops, like tomatoes, in the greenhouse, heating mats won’t do the job. Those plants will require warmer air to survive and produce fruit, so you will need a heater.
Many of these must-haves require electricity to run. That means wiring the greenhouse with outlets or running an extension cord from the house.
There will likely be times when the level of light streaming into the greenhouse will be too intense. It can scorch plant foliage and raise the air temperature to levels beyond what good ventilation can offset. Invest in shade cloth. It comes in varying densities, is easy to use, and can be a great tool in your arsenal to manage the temperatures within your greenhouse space.
If you haven’t listened to my conversation with Sheri George about owning a hobby greenhouse, you can do so now by scrolling to the top of the page and clicking the Play icon in the green bar under the page title.
Do you have a hobby greenhouse? Let us know about your experience in the comments below.
Links & Resources
Some product links in this guide are affiliate links. See full disclosure below.
joegardener Online Gardening Academy™: Popular courses on gardening fundamentals; managing pests, diseases & weeds; seed starting and more.
joegardener Online Gardening Academy Organic Vegetable Gardening: My new premium online course. The course is designed to be a comprehensive guide to starting, growing, nurturing and harvesting your favorite vegetables, no matter what you love to eat, no matter where you live, no matter your level of gardening experience.
joegardener Online Gardening Academy Master Seed Starting: Everything you need to know to start your own plants from seed — indoors and out.
joegardener Online Gardening Academy Beginning Gardener Fundamentals: Essential principles to know to create a thriving garden.
joegardener Online Gardening Academy Growing Epic Tomatoes: Learn how to grow epic tomatoes with Joe Lamp’l and Craig LeHoullier.
joegardener Online Gardening Academy Master Pests, Diseases & Weeds: Learn the proactive steps to take to manage pests, diseases and weeds for a more successful garden with a lot less frustration. Just $47 for lifetime access!
joegardener Online Gardening Academy Perfect Soil Recipe Master Class: Learn how to create the perfect soil environment for thriving plants.
Yoderbilt – Joe Lamp’l’s greenhouse maker as seen in this post
Disclosure: Some product links in this guide are affiliate links, which means we get a commission if you purchase. However, none of the prices of these resources have been increased to compensate us, and compensation is not an influencing factor on their inclusion here. The selection of all items featured in this post and podcast was based solely on merit and in no way influenced by any affiliate or financial incentive, or contractual relationship. At the time of this writing, Joe Lamp’l has professional relationships with the following companies who may have products included in this post and podcast: Corona Tools, Milorganite, Soil3, Greenhouse Megastore, Territorial Seed Company, Earth’s Ally, Proven Winners ColorChoice and Dramm. These companies are either Brand Partners of joegardener.com and/or advertise on our website. However, we receive no additional compensation from the sales or promotion of their product through this guide. The inclusion of any products mentioned within this post is entirely independent and exclusive of any relationship.