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Turning Winter into Summer: How Greenhouses Work in the Winter

The Sears Greenhouse Complex at the University of Missouri. | photo by Becca Wolf, Bond LSC

By Becca Wolf | Bond

Picture this. It’s 25
degrees Fahrenheit outside and snow is falling in Columbia. The weathermen have
projected 4 inches of snow in the next 24 hours. As wind whips the snow around,
students hope the schools call a snow day the next day. Snow starts to
accumulate as the sun sets and people all throughout town are staying inside,
some eating soup with their families, others curled up with a book near a fire.
Looking out their windows, they see their lawns covered in a blanket of snow.

All the plants outside
are dormant or dead, but plant research does not stop when the seasons change.
In fact, greenhouses make winter a highly productive season, despite Mizzou
being located in the not-so-balmy Midwest. Complex systems help balance the
temperature and lighting plants need to survive when it is not naturally

You only have to go as
far as the roof greenhouses on Bond Life Sciences Center to see an example of
the total 91,250 square feet of plant growth facility space at Mizzou, part of
more than 70 greenhouse rooms that are used year-round. Locations include the
Sears Greenhouse Complex, the Ashland Road Complex and the new East Campus
Growth Facility, and house everything from corn and soybeans to tomatoes,
broccoli and model plants like Arabidopsis.

“Probably 95% of
greenhouse space is research,” said Michelle Brooks, MU’s greenhouse
coordinator, “And then about 5% of the space is used for teaching undergraduate
plant science classes that have a hands-on lab in the greenhouse.”

To optimize growth, the
heating and cooling temperature is kept within an 8-10-degree Fahrenheit range.
Brooks explains, “you have to have that distance between it so the systems
don’t battle each other, because there’s much more fluctuation in temperature
in a greenhouse.”

These systems help keep
the temperature balanced, especially once it gets cold outside. Greenhouses
have to be kept as close to outside summer conditions as possible.

“You’re working to keep
them warm and light enough to grow the crops year round because most of these
plants, like corn and soybeans, they’re really high light plants,” said Brooks.

To maintain favorable
lighting, greenhouses at MU have high intensity (HID) lights that provide both
light needed for plants to grow. These lights mimic the sunlight plants would
get outside during the summer. The lights have a nice side effect, said Brooks,
“turning the lights on raises the temperature in the rooms by 10 degrees,” further
promoting plant growth.

Another way greenhouses
are heated is through hot water heaters. This system works by pumping hot water
through thin pipes that are around the perimeter of the greenhouse. These pipes
then radiate heat from the water into the room. The pipes allow heat to get
closer to the plants than the HID lights because there is no concern of
singeing or burning. MU also uses steam pipes in some greenhouses, which use
the same process except with steam instead of water.

To prevent this heat from
escaping, shades are used on the roof of the greenhouse. These shades act as
insulation to save energy and keep heat in. Greenhouse shades are often made
out of polypropylene, saran, polyethylene, and polyester and prevent direct sunlight
from getting in, along with insulating the greenhouse. Shades are used
year-round because in the summer, they help keep the greenhouses cool and keeps
the temperature balanced, even if it is 90 degrees Fahrenheit outside.

Shades drawn over the ceiling of a greenhouse at Bond LSC. | photo by Becca Wolf, Bond LSC

Wet walls are also used
in the summer to cool the greenhouses. These are comprised of cooling pads in
an aluminum wall that circulates water through it. There is a fan on the
opposite side of the wall that blows the cooled, evaporated water into the
greenhouse, thus lowering the temperature. These are typically the length of
the wall and are about 4-5 feet in height.

A wet wall in a greenhouse at Bond LSC. | photo by Becca Wolf, Bond LSC

How to Prepare for

When heavy snowfall
occurs, MU wants to prevent snow from accumulating because it blocks out the
sun and cools the greenhouse.

Brooks explains, “we
would disable the heat retention function of the shade cloth, because we want
the heat to go up into the peak to melt the snow off the greenhouse and out of
the gutters.” Luckily, this can be done automatically as most of the greenhouse
system is computerized. “It’s pretty automated,” said Brooks, which is helpful
because that means no one has to be at the greenhouse to make these
adjustments. For example, if there is a lot of snowfall in the middle of the
night, caretakers like Brooks do not have to wake up and drive to MU to pull
the shades.

To make sure the
greenhouses maintain their heat in cold temperatures, Brooks lists preventative
measures taken, “you have to make sure that people are not propping doors open
or turning on their exhaust fan because they’re working hard and you know, get
hot for a minute, and then forget to turn it off.” Doing this saves energy and
keeps the plants in a stable environment.

New MU Facility

Last fall, the new East
Campus Plant Growth facility opened. Being a total of 22,880 square feet
featuring 24 greenhouses and 27 growth chambers, there is a lot of space to
keep warm in the winter.

Fortunately, thanks to
new technology, there have not been many problems this winter there. “We had
some heat valves that were wired wrong,” Brooks says. “Luckily, it was the
hallway that was getting too cold, it wasn’t a room that was occupied.” These
heat valve issues were caught early and have been fixed, and there have been no
issues since.

The East Campus Plant
Growth facility is full of advanced technology, including exhaust fans with
variable speeds, instead of just ‘low,’ ‘high,’ or ‘off.’ This allows
coordinators to change the speed by increments so they, “can have the fan come
on slowly to where it doesn’t drop the temperature too fast because you don’t
want the cooling and the heat in wintertime to battle each other.” The gradual
increase and decrease in speed balance temperatures and gives scientists more
control in their plant growth.

Another system that is
new at the East Campus facility is the reverse osmosis (RO) water system. This
system takes out minerals in water and purifies it, which plants like.
Purifying the water also gives scientists more control in their plant growth
because it gives plants clean water, eliminating detrimental factors. The new
facility also has higher walls and ceilings, creating the potential to do
research on trees and other tall plants, like biofuel grasses.

Aside from new
technology, the East Campus facility has several other benefits as well.

“We have the potential
now for new hires that could potentially come in and bring in research
dollars,” Brooks said. MU does not have to turn away any researchers due to the
lack of facilities anymore. Space at the new facility also offers the
opportunity to expand in the future, and there are plans to add greenhouse
ranges as the need arises.

Now as the temperature
gets warmer and the days get longer, the greenhouses will have to be managed
accordingly. Water pipe heating will be turned off and the wet walls will be
turned on in order to combat the heat of Missouri summers.

But soon enough, it will
be winter again and the process will start all over.

Article originally published on Decoding Science.