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By Meg Brazill
There isn’t a New England gardener who hasn’t wished
for a nine-month growing season, or yearned for
fresh greens on a cold winter’s night. Some even
dream of orchids and the smell of jasmine. With New
England’s short growing season, it’s easy to see why
more and more gardeners – and green thumb wannabes –
are building backyard greenhouses.
How Your Garden Does Grow
If you’re considering a greenhouse in your future,
it’s time to give some thought to its function. Do
you want a temperature-controlled year-round
greenhouse or do you prefer puttering with potted
plants a few months of the year? The function will
determine the type and size of greenhouse you
choose.
If you’re looking for a simple space where you can
read and enjoy plants, an attached greenhouse or
sunroom might be right for you. A freestanding
greenhouse could be ideal for starting seeds early
before the last frost of spring.
A serious hankering for fresh greens and herbs,
nearly year-round, calls for a solar greenhouse,
which requires little or no additional heat.
Are you captivated by the idea of cultivating
orchids or experimenting with exotic plants? If so,
a professional-quality greenhouse that is
well-insulated and temperature-controlled year-round
will take you to the tropics. That kind of
undertaking requires running water, a power source,
supplemental lighting, and active ventilation.
Whatever course you decide on, plan for the long
term. Greenhouse owners say it’s easy to outgrow a
greenhouse if you don’t plan ahead. If your budget
calls for compromising your dream, go with a
greenhouse that can be extended later.
Picture This
Companies now offer so many styles of greenhouse
kits and plans, that there’s little reason to design
one from scratch. However, if you’re building a new
house, talk to your contractor or architect.
Building a greenhouse that is sympathetic to your
new home’s architecture and
its surrounding site will enhance the property.
Be sure to ask local gardeners and nurserymen what
products they recommend, as well as searching on the
Internet. Options range from elaborate Victorian
greenhouses to a simple set of plans you can modify
yourself. At this point, function combines with
aesthetics – and your budget – to narrow your
options. Part of your decision should include what
kind of technical support the supplier provides, if
any.
Getting Attached to your
Greenhouse
Having a greenhouse connected to your home is
advantageous, particularly over a long winter. It’s
a treat to easily wander in whenever you want and,
with the plants just steps away, plant care is a
breeze. Electricity and water are also readily
available.
An attached greenhouse can add free heat to your
home on a sunny winter’s day. However, if it’s not
properly set up, it can keep your furnace working
overtime on a cloudy day in winter.
Free and Clear
Freestanding greenhouses are much easier to set up
than attached ones, and fit any size budget. Climate
and location must figure prominently in your plans.
To withstand freezing New England winters, a
year-round greenhouse requires an insulated
foundation. Other costly items that a year-round
greenhouse may require are: weathertight double
glazing, insulating shades, buried power and water
lines, and heat.
Rectangular freestanding greenhouses are stable and
designed to withstand a snow load. For tight spaces,
lean-to models are inexpensive (starting under
$1,000), but won’t do as well under heavy snow load
conditions. Always check with the manufacturer for
these details.
A good rectangular freestanding unit starts around
$2,000 - $3,000; top-of-the-line models can exceed
$8,000.
From the Outside In
A contemporary style greenhouse may look great in
the landscape, but it’s a bad fit if your house is a
19th century cape. Snow load is a major
consideration when choosing a greenhouse in the
North. If snow won’t slide off the roof easily,
you’ll have to shovel it to protect the glazing and
allow light in.
Remember: the shape of the greenhouse also dictates
the interior space, including headroom, and how you
can use it.
Freestanding greenhouses are much easier to set up
than attached ones, and fit any size budget. Climate
and location must figure prominently in your plans.
To withstand freezing New England winters, a
year-round greenhouse requires an insulated
foundation.
Greenhouse frames are usually made of either wood or
aluminum. The advantage of wood is that you won’t
lose significant heat through the frame. The wood
must be painted or finished, or you may lose it to
rot or warp. Aluminum retains its shape and won’t
corrode. Some manufacturers now use neoprene gaskets
to minimize heat loss through an aluminum frame.
Life in a Glass House
You won’t be able to throw stones in a greenhouse
with glass glazing, but glass continues to be the
traditional glazing choice for many. New
horticultural plastics are high-quality and offer
competitive features. Considerations for choosing a
glazing include appearance, lifespan, single- or
double- or triple-glazing, how weathertight you need
it, and, of course, price.
Glass
On the plus side, glass transmits light beautifully
and well – and, it lasts almost indefinitely. The
traditional greenhouses with multi-pane glass are
hard to seal, but modern attached greenhouses are
usually very weathertight. Frost heaves can break
the glass unless the greenhouse sits on a
permanent foundation, so you may have to build one.
Plastic
Plastic glazings are far less susceptible to
extremes of temperature. They are non-breakable and
are lighter weight than glass, so they are easier to
handle. They also diffuse light well.
Fiberglass, which is flammable, has good shatter
resistance and it diffuses light well. Polycarbonate
plastics are transparent and nearly unbreakable.
Acrylics are similar to polycarbonate plastics, but
are not as resistant to fire or breakage. Milky
white and flexible, double-walled polyethylene
diffuses light well and is also resistant to
ultraviolet light.
Accessorize
Some greenhouse kits include accessories; others
offer just the greenhouse shell. When you’re
comparison shopping, find out if any of these are
included: benches or shelves for plants,
a small fan for circulation, automatic solar-powered
vent openers, a heater, a minimum-maximum
thermometer, and shade cloth to filter summer sun.
Greenhouse Gardening
Gardening with an eye toward the eclectic sounds
like the right idea, but it’s likely to fail in a
greenhouse. Cold nights and bright lights will be
right for some plants and fatal to others. Within
every greenhouse, there are small microclimates that
will be more conducive to some plants. By using
these natural microclimates to your advantage,
you’ll be able to grow a wider range of plants
successfully.
Books about Greenhouses
and Greenhouse Gardening
Greenhouse Gardener’s Companion:
Growing Food and Flowers in your
Greenhouse or Sun Space
By Shane Smith,
Marjorie C. Leggitt (Illustrator)
(Fulcrum, 2nd edition, April 2000)
544 pp., paperback
Gardening in your Greenhouse
(Greenhouse Basics, No. 2)
By Mark Freeman
(Stackpole Books, 1998), 208 pp.
Greenhouse Gardening
By Miranda Smith
(Rodale, 1985)
The Greenhouse Expert
by D. G. Hessayon
(Sterling Publications, March 1994), 128 pp.
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