Greenhouses: creating the perfect climate for plants
by: Sarah Sharman, PhD, Science writer
Illustrated by: Cathleen Shaw
Although my house is now filled with healthy, thriving plants, my track record with plants was not always this good. I had what people call a black thumb. Plant after plant would enter my house, and within a month, they would turn yellow and die. It wasn’t until I moved into a house with the perfect lighting and open-air floor plan that I realized I was watering my plants too much and not providing them with the optimal light to counteract the constantly soggy soil. What a difference a watering schedule and natural light made to my plant babies!
Both houseplants and agricultural crops alike require specific light and temperature conditions, and ample water and nutrients to survive. Sometimes indoor conditions and even the outdoor climate are insufficient for plants to grow and thrive. Creating the perfect environment within an artificial structure called a greenhouse is an effective strategy for many amateur gardeners and farmers who want to start seedlings during cold months, overwinter perennial crops, or grow plants outside of their natural growing zone. Let’s learn about greenhouses and the many features that make them the perfect artificial home for plants.
What is a greenhouse?
A greenhouse (also called a glasshouse) is a structure with a roof and walls made of transparent material, like glass or plastic. Greenhouses use sunlight to create a climate-controlled environment for growing plants. Many industrial greenhouses are made from glass because they allow a high amount of light to enter and trap heat inside the structure. However, plastic greenhouses are also effective for amateur gardeners to grow plants outside year-round. Plastic greenhouses don’t trap as much heat as glass greenhouses, so they often require an additional heat source during cooler months.
Let’s have a little sidebar physics lesson to understand how sunlight warms a greenhouse. Light waves enter the greenhouse through the glass. These light waves bounce around inside the greenhouse, becoming longer-electromagnetic waves that get absorbed by plants, pots, the ground, or any other objects in the greenhouse. The objects convert light energy into heat energy and release it back into the greenhouse atmosphere. Most of the heat remains trapped within the greenhouse because it cannot escape through the glass walls and ceilings.
With sufficient sunlight, the temperature inside the greenhouse may become much higher than the outdoor temperature. For this reason, greenhouses are often equipped with ventilation systems so the plants won’t get cooked by the stifling temperatures on hot days.
A process called convection also helps to keep greenhouses warm. The warm air at the bottom of the greenhouse rises to the top and pushes the cooler air back to the bottom. The cooler air is then heated by the absorption of sunlight, and the process repeats itself continually. High greenhouse ceilings can help maximize the effectiveness of convection. Giving air more room to move increases airflow and prevents hot spots that could negatively impact the growth and survival of plants.
Sunlight is a great heat source for greenhouses during warm months and during the day, but what happens when the sun goes down, or temperatures outside dip low? Many greenhouses in colder regions are equipped with supplemental heating that can fill in the gaps when the outside temperature threatens to cool down the greenhouse too much. Floor heating systems help maintain the convection process by heating the air at the base of the greenhouse so it can rise to the top and displace the cooler air. This is more efficient than ceiling heaters alone.
We’ve talked about all these cool greenhouse features, but you may wonder why they are so important for growing plants. First and maybe most importantly, the light and warm temperatures created by the greenhouse provide plants with the right conditions for photosynthesis to occur. Photosynthesis is the process by which plants make food from sunlight, carbon dioxide, and water. It is their primary energy source; without it, we would not have plants.
Greenhouses can also help extend the growing season for many temperate parts of the world. They protect plants from adverse weather events, insects, fungi, and common plant diseases that are prevalent when growing plants in nature. A greenhouse’s temperature and moisture levels can be manipulated to grow a wide diversity of plants within a single greenhouse.
You can see how greenhouses are a great tool for hobby gardeners to do things, like start seedlings or protect their more finicky plant babies during the winter months. Now let’s discuss how plant scientists use greenhouses in their research.
How do scientists use greenhouses?
Agricultural and plant researchers benefit greatly from the availability of greenhouses for many of the same reasons we discussed above. In many ways, hobby greenhouses and industrial/research greenhouses are very similar. However, research greenhouses usually come with all the bells and whistles, sometimes above and beyond what an amateur gardener might need or afford. HudsonAlpha Institute for Biotechnology recently finished construction on a large, state-of-the-art greenhouse that will greatly expand the breadth of plants that scientists there are able to grow and study.
For plant researchers, greenhouses provide more controlled conditions than those provided by outdoor gardens or field plots. In some of the most high-tech greenhouses, everything from temperature to water levels to fertilizer and pesticide applications is controlled automatically through computer systems. The climate is monitored 24/7, and an alert is set off if the temperature or humidity levels deviate too far from the set point.
Large research greenhouses can oftentimes house dozens of different researchers’ plants. Each individual room has its own temperature, humidity, and light controls so that the environment can be unique for each type of plant. At HudsonAlpha, this means that Alex Harkess, PhD, can grow tropical plants in hot and humid climates, while next door Kankshita Swaminathan, PhD, can keep her grasses happy at moderate temperatures.
While greenhouses supply all of the light that a plant might need during the day, researchers are obviously limited to the hours when the sun is up. In order to provide plants with lighting outside of normal daylight hours, supplemental lighting must be installed in the greenhouse. Providing plants with more daylight can speed up the lifecycle of plants. For HudsonAlpha Faculty Investigator Josh Clevenger, PhD, supplemental lighting is essential for his peanut speed breeding projects. By simulating 20 hours of daylight, Dr. Clevenger can manipulate the flowering time of peanuts and minimize the time it takes to breed new peanut lines.
Access to greenhouse space is crucial for plant researchers no matter what part of the world they work. Being able to create a controlled environment for research studies is very important. Without greenhouses, scientists would have difficulty creating appropriate climates and protecting plants from the pests that are so prevalent in nature. Plant scientists’ work, including those at HudsonAlpha, is critical for our future generations to ensure that they have sufficient food, fiber, and fuel. Sustainable agriculture research aims to provide solutions to help mitigate future climate change while providing answers to farming in our current climate environment.
To learn more about the other features of the HudsonAlpha Center for Plant Science and Sustainable Agriculture Greenhouse and Educational Learning Labs, click here.