can’t be afraid to expose yourself to new ideas,”
John Biernbaum tells us whimsically as he presents a photograph of
the rear view of a barelegged man holding open his trench coat to
a facing sign reading “New Ideas.” Thus begins a fun-filled
day at Organic University, the pre-conference program to the 16th
annual Upper Midwest Organic Farming Conference held January 24-27,
2005 in La Crosse, Wisconsin.
Biernbaum is professor of horticulture at Michigan State University,
where he is also the advisor to the Student Organic Farm, a 48-week
CSA developed and operated almost entirely by students. Under his
guidance, the Student Organic Farm is now in its fourth season of
research and second year as a CSA and serves not only to produce food
but also as a place to practice new farming methods.
During the first CSA year, 40 percent of the Student Organic Farm’s
crop came from the greenhouses, which were only 20 percent of the
farm’s first-year production area. Greenhouse production has
proven an important asset, and it is to learn about year- round
greenhouse production that we are all seated before Biernbaum.
I am at Organic University, the prequel to the 16th annual Upper
Midwest Organic Farming Conference in La Crosse, Wisconsin. While
most of the 60-member, sold-out-in-advance audience has either decided
to build a greenhouse or is looking for ways to improve their greenhouse
crop production, the whole concept of greenhouse vegetable production
is fairly new to me. I am a neophyte (a fancy way to call myself
inexperienced) to greenhouses, and just as Biernbaum advises, I
am ready to expose myself to this new idea in farming.
Fortunately for me, Biernbaum starts at the very beginning by defining
a greenhouse. For the sake of the workshop, he explains, he will
use the term greenhouse broadly, referring to greenhouses, high
tunnels and hoop houses, (though each structure can be unique, he
says). Greenhouses are gothic or Quonset structures with end walls
and a double-layer polyethylene inflated roof. They are well sealed
against winter weather to encourage year-round growing, and they
may be heated. High tunnels are generally smaller, single-layer
film covered cold frame structures or multi-peak single layer structures,
often with limited structural end walls. Hoop houses are like greenhouses,
but they may be covered with single or double layer inflated film,
may have minimal end walls, and are usually unheated. All three
may have roll-up sides for summer ventilation.
With those distinctions made, we are ready to delve into Biernbaum’s
first topic of the day: site selection.
“The first step in effective greenhouse vegetable production
is selecting a greenhouse-friendly location,” Biernbaum tells
us. As I am about to discover, choosing a site requires more than
just finding enough room to build a structure. Biernbaum describes
four major components of a good greenhouse location.
Let it flow
First, Biernbaum tells us to think about drainage.
“Water removal is crucial! I can’t stress that enough,”
he says. The Student Organic Farm had no drainage system its first
winter, he says, and the crops paid the price during the spring
thaw. The lower end of the greenhouse flooded and production there
was weeks behind.
It is best to build your greenhouse on elevated ground so runoff
flows away from the structure, Biernbaum advises. Don’t forget
about the extra water coming off the roof either, he says, especially
if you have heavier soil.
If no slope can be achieved, he says, it is critical to provide
“To solve our flooding problem, we installed four inch drain
lines around each house,” Biernbaum explains. The lines are
covered with crushed gravel and have eliminated flooding while also
deterring tunneling rodents and preventing grass from growing into
the houses. Whaddya know. Solutions to two challenges I never knew
Getting(and plugging) in
Next, Biernbaum tells us to consider the accessibility of the greenhouse
site—to both people and utilities.
Make certain, he says, that the roads leading to your greenhouse
are suitable for all seasons (remembering that they may be used
twice daily to manage frost fabric, to roll up the sides of the
house, or to open the end walls for ventilation).
Irrigation water is necessary in the winter, Biernbaum says; so
therefore are frost-free hydrants (in USDA Cold Hardiness Zones
where appropriate) and 4-feet-deep water lines. Remember to backfill
with gravel around the base of the hydrants so they drain well,
he says. The farther a water source, Biernbaum says the more hose
necessary to adequately drain at each irrigation. You may also need
electricity for the inflation of polyethylene and/or for heat, he
says, and will require a tank or line for propane or natural gas
(more about these choices later).
Also, Biernbaum says, make sure you build your greenhouse where
you will have easy access to a washing and processing area and to
your storage cooler or root cellar.
Shade and light
According to Biernbaum, if you will be doing winter farming you
want to orient the greenhouse to maximize light interception during
the winter months (orientation refers to which way the ridge of
the greenhouse runs). At northern latitudes (above 40 degrees),
he says, an east-west orientation works best to catch maximum light
during winter. With an East-West orientation, Biernbaum explains,
the winter light will penetrate the length of the south side of
the greenhouse instead of shining through from the end.
“While an east-west orientation works best in most northern
latitudes, there may be some exceptions,” Biernbaum says.
“If heavy snow is an issue and wind can help move the snow
away, an alternative orientation might be used.”
You should also consider the direction and strength of the wind,
he says, as wind may play a key role in the preferred orientation
of your structure. Wind blowing over a greenhouse is like wind going
over an airplane wing, Biernbaum says, and while you can modify
impact with windbreaks, wind is still something to keep in mind.
He adds that if your greenhouse is in warmer or southern latitudes,
a north-south orientation may provide good light and the best ventilation.
It is also important to consider shadows and shade from trees,
hills and buildings, Biernbaum says, including the shadows one greenhouse
may cast on the next. Shade limits the amount of sun your greenhouse
receives, he says, thus limiting its production. Remember, he advises,
that shade lines differ between summer and winter and that the longest
shadow day is December 21. When selecting a site, Biernbaum recommends
that the greenhouse be located at a distance equal to at least twice
the height of any potential shade source.
Know thy soil
And of course, you want your greenhouse site to have either excellent
soil quality or the potential to become so. If the area is already
cultivated and the soil is healthy, Biernbaum says, little preparation
If you have growing experience, he says, the easiest way to determine
soil quality is to let some crops do the analysis for you. Nutrient
and texture analysis are also possible if you don’t have experience;
while this gives you immediate answers regarding the quality of
your soil, you’ll have to invest $30 to $50.
“If you have the time and experience, work up the ground
and plant something and see how it grows,” Biernbaum says.
Unless you find a site with exceptional soil quality and natural
drainage, Biernbaum recommends choosing a greenhouse site at least
one year before building the structure so you have adequate time
to improve land and reduce weed pressure.
“If the site is in sod or pasture and has not been cultivated,
it is particularly important to start in advance so the sod has
time to break down,” Biernbaum tells the class. “Plowing
or tilling is one way to break the sod, although sheet composting
[thick layers of mulch] without cultivation is also an option. Regular
cultivation and irrigation will help reduce the weed seed bank,
and additions of organic matter from green manure or compost helps
build soil organic matter and nutrient availability.”
Biernbaum closes this section of his lecture with a final site-selection
“Greenhouses with posts pounded into the soil are generally
considered temporary structures with regard to taxes, but zoning
ordinances are often done on a township level, which means sometimes
farmers need to be ready and able to explain things.”
Whew! Lots of thought goes into just choosing and preparing a site,
and that is the easy part! Next, Biernbaum will talk about constructing
a greenhouse. I flip to a fresh new page in my notebook, lean back
in my chair, stretch my arms out a little and prepare to expose
myself to the next step.
Katie Olender is a senior majoring in agricultural communications
at Michigan State University.