January 12, 2004: It was the heaviest snow
of the season in Pennsylvania. Twenty-seven inches of the
white stuff covered the ground last February as George crept
down the one open lane of our two-lane state road in 4-wheel
drive. He was responding to a fire call, but the farmer in
him couldn’t help but notice on the way to the firehouse
that a neighbor’s greenhouse had collapsed overnight.
The middle of the 96-foot structure was smashed flat to the
ground. The end walls of the structure slanted inward, warped
at odd angles by tons of snow. Ouch!
It was any grower’s worst nightmare.
Heading home a few hours later, George looked at the neighbor’s
trashed greenhouse from the opposite direction. What he saw
sent another shiver down his spine. A second house lay in
“Are our four houses still standing?” he wondered.
They were, thankfully. We’ve learned to give Mother
Nature a little sass (with a lot of elbow grease). Because
while nothing is totally safe from the rages of Mother, be
it heavy snow or howling wind, there are certain things you
can do to help greenhouses—this includes high tunnels,
hoophouses and coldframes—stand up to those rages.
In earlier columns, we’ve addressed what we grow under
cover. Welcome to Greenhouse
101, where we share all of the little
and not so little things we never imagined we’d have
to deal with when we built our first greenhouse in 1995. Some
lessons we learned the hard way. Fortunately the process hasn’t
been that painful or expensive, for us at least (so far).
We first learned about wind when the 100- by 40-foot plastic
skin from a friend’s hoophouse ended up in the treetops
200 yards away from the house’s steel skeleton. (OK,
something close to that happened to us once, too. So smile
smugly if it hasn’t happened to you—yet—and
If you live in a wind tunnel, attach greenhouse plastic as
firmly as possible all around the structure. Batten down anything
that will flap in the wind. And secure those roll-up sides,
matey. Use ropes, bungee cords, cement blocks, long stakes,
whatever it takes.
Keeping a greenhouse covered year-round requires year-round
management. If it’s a heated structure, you need to
keep propane in the tank (or wood or coal in the firebox),
whether you have crops in the ground or not, in order to fend
off the snow and ice.
Dealing with Snow
We’re starting with snow, since it’s that time
of year already. On December 7, 2003, the first snowstorm
of the season gave us a whole foot of the white stuff. (We
got off lucky; the rest of Northeast wasn’t so blessed.)
That’s when we noticed our neighbor’s greenhouse
frames that collapsed earlier this year were bare going into
this winter. Ah, experience, the great teacher. The neighboring
grower farms rented ground and simply lives too far away to
deal with greenhouse upkeep when foul weather can make driving
If you can’t be there to respond to changing weather
conditions, don’t tempt fate; uncover the frame for
Plastic is cheap, a whole lot cheaper than greenhouse frames
in the grand scheme of things. Be sure to save the old plastic;
it’s virtually indestructible. You can reuse it for
any number of things, such as covering coldframes, new end
walls, storing equipment, or adding an extra layer of protection
for ground-planted crops in hoops (inside the greenhouse or
outside). We even used old plastic as a ground cloth to keep
the new plastic out of the mud when covering our largest greenhouse.
Don’t buy trouble. The neighboring greenhouses that
collapsed were poorly designed. Their shallow-peaked roofs
just could not shed snow efficiently; that’s why they
now stand uncovered and useless.
In contrast, heavy snow and ice slide fairly easily off of
our three gothic-arch high tunnels and even off of our quonset-shaped
hoophouse. Of course just to be on the safe side, we often
find ourselves helping the process along with a long-handled
snow brush, a broom, or by banging a gloved hand on the plastic
skin from inside the hoophouse to start an avalanche. The
snow slides down from the peak and piles up harmlessly along
the sides. We’ve had that hoop up for eight years and
replaced the plastic only twice: once because of old age and
once because of wind damage; never because of snow.
In our two heated double-poly greenhouses, we also manipulate
temperature and inflation to fight snow and ice. This has
been a process of classic on-the-job training. Snow, sleet
and slop started almost as soon as we covered our first house
in March 1998. We sent a frantic email off to our friend and
mentor Cass Peterson, who was running Flickerville Mountain
Farm and Groundhog Ranch in Dott, Pa. (For
the full story of the Groundhog Ranch, visit the bookstore
A Farmer’s Odyssey, a collection of Ward Sinclair’s
award-winning Washington Post columns about the joys and sorrows
of producing organic food for body and soul at Flickerville.)
As usual, Cass promptly answered our prayers…with the
following email: “When the overnight temperatures are
mid to upper 20s and the snow is wet and minimal (less than
six inches accumulated), better to leave the inflation on,”
she wrote. “Otherwise the snow will settle into the
little valleys you have created between the struts with the
loose plastic and add even more weight to the house.
“The time to let out the inflation is when the snow
is heavy (more than six inches) with temps at 25 degrees or
less and especially with no wind.
“Here’s why: If ambient temps are 25 degrees
or lower, chances are that the outside layer of your poly
is right at freezing. Snow will stick at this temperature.
Weight increases. If there’s no wind, none of the snow
is likely to fly off. You need to “create” snowslides
off your greenhouse by having the plastic temperature higher
than 32 degrees. Thus, deflate and let the interior heat warm
up the outside layer.
“If the ambient temps are above 25 degrees, chances
are that your outside poly layer is above 32, and slides will
occur better on the humpy slope of your inflated greenhouse.
“The real bugaboo is sleet/freezing rain,” she
warned. “That’s when you jack up the temperature
inside and collapse the inflation—to a point. If it’s
a light sleet, the higher temp inside will soften it, and
then, the next morning, you inflate to push the icy layer
harmlessly (no slicing through plastic!) off the house.
“If it’s a hard sleet, you have to cycle between
inflation and deflation. Yes, my man, even to the point of
arising in the middle of the night. Down for a few hours at
maximal heat, then up for an hour or two to slide off the
softened slush. Then down again to build up heat, then up
Thanks, Cass. Your sage advice, and that of other helpful
growers around the country, helped get us through the past
six seasons without any major disasters. (Never mind all of
the minor greenhouse gaffes, although you, dear reader, will
probably hear about most of them right here eventually.)
Don’t be afraid to ask for help, whether in the form
of long-distance advice or nearby helping hands from family,
friends and neighbors.
We can’t stress the “helping hands” enough
because this year we will be recovering all four greenhouses.
The inside layer of plastic in Melanie’s seed-starting
house is sun-rotted along the ridge, we just noticed. That
means it is leaking both air and heat. The outside skin is
probably not inflating quite as tightly as it could, so we’re
also losing heat there. After six full years of use, though,
we’ve gotten our money’s worth out of the plastic
(it’s only rated for three years).
Plastic sheeting elsewhere around the farm is variously patched,
discolored, stretched, stressed, torn and just plain worn
out, kind of like the farmers at this time of year. But thinking
of the job ahead as a modern-day barn raising—complete
with a big brunch and a bunch of warm-hearted friends—already
gives us something delightful to look forward to in the new
So, let it snow and blow. The propane tanks are nearly full.
Brooms and snow brushes stand at the ready (a snow shovel,
too, so we can dig our way into the houses). We’ll order
and pay for the new plastic by early January—in order
to take advantage of an eight percent discount from our local
greenhouse supplier—and we’ll be all set to go
when we’re pale, rested and ready.