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.