In a tongue-in-cheek manner, Norm has often declared that if it weren’t for crappy weather we would not have a business.
The plain reality of the fact is, people, use greenhouses to mitigate the negative impact of weather, and nature in general, on their food and plant production.
Greenhouses allow a person to control the local environment. The more efficient they are at that process, the more profitable they can potentially be.
The main areas of this control are heating, cooling, irrigation, disease and insect and weed control. When all of these areas are exercised efficiently, production can be significantly increased and the timing of production can be better controlled.
Heating is typically the number 1 expense in operating a greenhouse in colder climates in the wintertime. Numerous covers will reduce heat loss but it is often at the expense of light transmission. The cost of certain covers may not be justified in light of the heat savings they would create. There are creative ways that the area which needs to be heated can be reduced. Growers will often choose crops with lower heat requirements to reduce the expense. Even though the heating is usually associated with cold weather, heating can also be used when dew is present to reduce the risk of fungus diseases.
Cooling a greenhouse to acceptable levels is critical during warmer seasons. During warm times, this requires a minimum of one air change per minute. If the temperature goes about a plant’s high threshold, it will stop growing for up to two weeks. There is a wide range of options for cooling a greenhouse. Many of the passive methods are more economical to install but harder to control and fine-tune. Items like roof vents are extremely effective, and have a low operating cost but are costly to install and even more costly to automate. In addition to creating uniform air changes, it is equally important to have uniformly even moving air. Stagnant air fosters diseases.
Having an area covered with a greenhouse, allows the grower to control the water to the plants. Irrigation requires the proper timing and volume of water to the plants and also proper location. Many plants perform much better when the foliage remains dry.
Greenhouses can also protect plants from excessive rain during wet seasons. One often overlooked area of irrigation is existing groundwater. When there is a high water table, care must be taken not to over water plants.
Greenhouses provide management opportunities for disease and pest control. Especially with a proper irrigation protocol, the risk of diseases can be minimized. If insecticides or fungicides are being used, it is much more controlled in the controlled environment of the greenhouse. Systems of netting can be installed over the ventilation openings to prevent the entry of airborne pests. It is important to bear in mind that this netting does restrict airflow as well.
A greenhouse also allows for more control of the weed population. Weed seeds can be allowed to germinate in the beds and then rototill them under. In the protected environment of a greenhouse, it is easy to put down black plastic for a short period of time to kill off weeds and weed seeds. It is also important to remember that if netting is used over the roll-up side openings, this will restrict airflow. Proper airflow takes priority over weed control.
When all of the above points are worked together efficiently, the grower will be able to significantly increase his or her yields. There will also be the opportunity to control the timing of the harvest to take advantage of increased pricing. i.e having a crop ready 2-3 weeks ahead of field-grown crops will easily cover the added expenses of growing in a greenhouse.
Disclaimer: we are not professional growers. The above information should only be used to draw attention to the importance of certain concepts. It is critical to seek out the advice of a professional grower to work through issues.
If you’d like to read more about these topics, let us know. We hope to have a book about this put together in time for Christmas and Winter Planning!