The difference between growing indoors and outdoors is like the difference between artists using a small canvas versus painting the Sistine chapel.
Most hobbyists couldn't manage a greenhouse with more just than a few plants and even a commercial-scale indoor grower would have a lot to learn to make the transition to greenhouse production.
Although it is tricky to grow in a greenhouse, successful greenhouse production can deliver 10 times the yield of an indoor grow space.
Everything is faster and more magnified in an under-the-sun operation, but this can be a great thing if you learn a few key skills—temperature management, water management and simple observation are the three best things for a greenhouse grower to be good at.
Nothing on our planet is a better source of light than the sun. The sun can grow larger, healthier plants than any indoor light—but there are many problems that are accelerated by sunshine.
Temperature is the biggest problem when using solar energy, because a greenhouse is designed to trap heat while still allowing the plants inside to harvest light. High temperatures can be managed in several ways, depending on the region where your greenhouse is located.
Probably the easiest and most economical is a shade cloth—these come in various percentages of shading and will help prevent excessive temperatures, but they will also cause a loss of light intensity.
Some loss of light is usually acceptable if you are experiencing high temperatures, though, because your plants probably can’t efficiently use all the light they are being given. Some other cooling devices employed by greenhouse growers are vents to allow heat to escape and exchange air, fans to pull new air in (and push out the old), cool pads and air conditioners.
Cool pads are essentially water evaporators that have air pulled through them, which puts cooler air in the greenhouse but also increases the humidity drastically.
Air conditioners are mainly used in cooler regions because in a high-heat environment an air conditioner isn’t very economical to run 24 hours a day in a greenhouse.
Cold temperatures can also present a problem but are somewhat easier to manage. Most greenhouses employ standard warehouse heaters, which are expensive to run but effective.
These are often combined with a jet tube that helps redistribute the warm air evenly—a jet tube is simply a plastic tube, usually about two feet in diameter with circular holes cut down the full length, which is closed off at the end.
This essentially fills like a balloon and as the heaters are running it stays inflated, distributing the hot air. Other common methods of heating a greenhouse are heated floors or benches—think of sealed tubing built into the floor or the greenhouse bench, circulating hot water. Put this under the plants and the heat will rise, making the environment warmer for the plants.
Water management is tricky to learn indoors but it can become predictable after some practice. Growing in a greenhouse is a different experience every day, thanks to our friend Mother Nature.
Plants adjust to the conditions of the environment and so should your watering schedule—on a cloudy day a greenhouse grower may have to water once, when on a normal sunny day he might water six times.
The comparison to indoor growing is simple; artificial light indoors can only provide as much radiation to your plants as the sun on the cloudiest of days. This means if you are indoors and watering several times a day, it is too much!
The true key to growing, whether indoors or outdoors, is observation. You must look at your plants—and look at them often. You should ask yourself several things every time you look at your plants. For example:
- How are the leaves oriented?
- Are they tilted towards the light or folded away?
- What color are the leaves and are there oddly colored leaves or spots?
- Do you see any bugs?
- Is all the equipment running properly?
- What does the thermometer say?
All these things should cross your mind when examining your plants and in a greenhouse you had better not forget any of them—one bad day in a greenhouse can kill everything, whereas an indoor crop will likely survive one bad day, although it’s not very healthy for the plants.
The real reason to grow in a greenhouse is to make money. While some growers employ small greenhouses as part of their hobbies, real commercial-scale greenhouse production has the potential to generate a higher-value crop than any other agricultural system if conducted properly.
The amount of money to be made can be enticing, but there is also a high cost of entry into this market—greenhouses are not cheap and you could end up investing an astronomical amount of money, depending on how many automated controls you set up.
Growing in a greenhouse is a long-term investment of time and money and even the few growers that profit heavily will tell you that it’s often harder than it’s worth.