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
“Are our four houses still standing?”
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
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 read
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 dicey.
If you can’t be there to respond to changing weather conditions,
don’t tempt fate; uncover the frame for the winter.
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
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
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 for Truckpatch: 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
“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 again.”
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 year.
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.