Temperature
The increase in temperature seems to be the primary goal when people want to buy a greenhouse or construct a hoophouse. However, temperature control quickly becomes the primary focus once you put your first seedlings or plants inside. Even in northern growing zones, the temperatures can get quite unfavorable for green-growing things and you can end up with a lot of wilted plants ruining a lot of spring work.
The solution is two-fold: air ventilation and circulation. Ventilation is needed to evacuate heat out from inside the structure. It can simply be propping open windows in the structure or even sophisticated thermostatically controlled exhaust fans. Speaking of fans, many backyard greenhouses have a small electric fan strategically positioned to circulate air which helps ensure even temperatures in both cold and warm seasons. Circulation of air helps prevent hot or cold dead spots which can cause different 
results in different parts of your greenhouse even in a small structure.
Keeping a log of temperatures at various points of the day is a good idea. It allows you to pay close attention and monitor changes throughout the year and not rely on assumptions for planning. There are even affordable systems that can monitor temperature and send you an alert right to your mobile phone.
Humidity
Similar to heat, excess moisture in the air can create an unfavorable ecosystem in your hoophouse. One of the biggest concerns is the extra humidity creates a great fungi-growing environment. Many of these are harmful to what you want to grow. Any warm, moist environment can be a petri dish for growing molds and fungi that can cause crop failure.
Similar to heat, air ventilation and circulation is the primary solution. Rolling up sidewalls or exhaust fans are some of the more common solutions. In a rigid greenhouse, propping open windows can help, but air movement is critical. Even a small clip-on electric fan you can find at a thrift store can help a home-scale greenhouse keep the air moving.
Irrigation
Since most of these structures are excluding rainwater from the growing conditions inside, the soils can develop an imbalance of mineral concentrations. Rainwater usually helps keep mineral concentrations in balance, so the choice is to either artificially manage the chemical composition of your growing medium or to capture and irrigate with rain water inside your structure.
To help reduce humidity during critical times of the year and to reduce the water usage inside the greenhouse or hightunnel, drip irrigation at, or just slightly below, the soil surface is a great approach. These irrigation lines have become more common now and you can set irrigation up on a timer with filters or even fertilizer additives to the water.
If watering from the home water service, you should have a good understanding of what is and is not in that water before you apply it to your plants.
Pests
Whiteflies, aphids, and spider mites are three of the most common pests when it comes to growing in enclosed structures. There are other pests that attack specific plants, such as the tomato hornworm, but we’ll deal with generalities here.
Growers can use synthetic pest control, but I don’t recommend it. I prefer a two-stage approach. Stage one is what is known as biological control. Stage two would be the application of organic compounds.
According to the USDA’s Sustainable Agriculture Research and Education organization (SARE), biological control is “the suppression or eradication of crop pests using their natural enemies. This most often means the artificial introduction or encouragement of a predator pest species.
SARE teaches that biological control can save time by letting the predators do the work and the fact that the predators can work for long periods of time. It also means not risking using harmful chemicals and compounds.
To read a report of the study done by SARE about pest management in greenhouses and hightunnels, click here.
Greenhouses and hoophouses are great ways to extend your growing season or get seedlings started early without crowding inside your home’s sun-facing windows. Dive in and start today.]]>
