Ask a Master Gardener

photo of a greenhouse in the sunset

Greenhouses

11/14/23

Let’s say you’ve been growing your own vegetables for several years and are wanting to start being able to grow your own food 12 months out of the year. You have some options. Some are relatively inexpensive, while others will require a sizable investment on your part. Let’s talk about some of your options.

In an article a few weeks ago we talked about cold frames. These are small structure that enable you to not only extend the growing season in the fall but also allow you to start earlier in the spring. For more info, check that article. You can find it on the Tulsa World website as well as our Master Gardener website (www.tulsamastergardeners.org).

Next you have a variety of options for growing vegetables and herbs indoors. After a quick search online, it looks like you can get small and simple hydroponic growing systems starting at around $100. Hydroponic growing systems use water as the delivery system for both water and nutrients. In these systems, the plants are typically placed in some sort of growing medium that allows the water to flow through it and back into the water reservoir. Nutrients are placed in the water and a pump circulates the nutrient rich water on a variety of schedules. These entry level systems also come with a light source and timer allowing you to program the device to fit your growing schedule. These starter devices would be good for some herbs or perhaps greens.

From here, there are systems available known as hydroponic growing towers. These towers are designed for indoor use and come with a light source for your plants. Their costs increase along with the size. It would not be unusual to spend a $1000 or more on one of these systems. However, if you get a good one, they can be used to supplement your food needs year-round.

From here you could move to an aquaponic growing system, but this will require more of an investment and a fair amount of space since aquaponic systems involve using fish in the water to produce nutrients for your growing plants. If you’re not quite ready to get into hydroponic or aquaponic systems, you might want to consider building a greenhouse to enable year-round growing.

Greenhouses come in all shapes and sizes. Naturally, the bigger the greenhouse, the larger the investment required. One of the more economical greenhouses to consider is called a lean-to. Lean-to greenhouses are built up against an existing structure like your home or perhaps a stand-alone garage. The advantages associated with a lean-to greenhouse would be less of a financial investment and if it is going to be attached to your house or garage, you’ll likely access to existing electric, water, and HVAC systems. The downside could be that the layout of your home prevents such an attached structure or maybe there’s not going to be good natural light available due to trees etc.

Next up would be to build a free-standing greenhouse. Location will be key, and you want your greenhouse located on a well-drained, level site with full sun exposure. The best location for the greenhouse would be on the south or southeast side of your home. The east side would be second best because this will allow the greenhouse to catch the most sunlight in November through February. Next best would be the southwest and west and the least favorable location would be the north side of your home. It should also be located away from trees not only because you don’t want the trees to shade the greenhouse, but you won’t want any limbs to be able to fall and damage your greenhouse.

Next, you’ll need to decide what size of greenhouse you would like to have. Granted, the biggest determining factor for most of us will be cost. Just remember to leave enough space for a center aisle.

Heating your greenhouse will make it useable throughout the winter and most heating systems are satisfactory for greenhouses. Greenhouses can be heated with electricity, gas, or oil. Space heaters, forced air, or hot-water systems are all viable ways to heat your greenhouse. Radiant heat lamps can also be used if combined with soil heating cables under the plants.

If using space heaters that are fueled by gas, oil, or coal, be sure to provide fresh air and an exhaust ventilation system. Carbon dioxide poisoning is a real thing and that would certainly spoil your growing plans. Also be sure to install a temperature alarm system which will alert you if there are any power failures. These devices will be worth the investment, especially if you are growing a large quantity of plants or specialty plants like orchids.

While it may not seem like it, even during the cold weather, a greenhouse can get warm on bright, sunny days. A good ventilation system will help to control temperature and humidity in every season. Exhaust fans are also a good idea.

In the summer, a swamp cooler can help keep temperatures down in the greenhouse if you plan on using it in the summer too. Swamp coolers force air through a wet filter medium, using evaporation to provide cooler air. Swamp coolers date back to ancient Egypt and are a good way to help keep your greenhouse from getting too hot in the summer.

So, if you really want to continue to grow vegetables throughout the year you have some options. See you in the garden!

You can get answers to all your gardening questions by calling the Tulsa Master Gardeners Help Line at 918-746-3701, dropping by our Diagnostic Center at 4116 E. 15th Street, or by emailing us at mg@tulsamastergardeners.org. Photo: OSU Ag. Communications