Read an Excerpt

Greenhouse Gardener's Companion

Growing Food & Flowers in Your Greenhouse or Sunspace

Fulcrum Publishing

The Greenhouse or Sunspace Environment

Every greenhouse or sunspace is different. Take a close look at your unique sunroom. If you already have a greenhouse, take the time to notice the changes in the environment from season to season and day to day, from front to back and ceiling to floor. Pay attention to the climate where you live, because that also affects the environment within your greenhouse or sunspace. The first step in understanding how to garden in a sunspace is to get a good feel for its unique environment. Stop, see, and feel what is going on in there. Watch the shadows during the course of the day. Where do they rise and fall? Notice how they change through the seasons. If you do this, you'll observe how low the sun is at 12 noon in December versus how high it is at the same time in June. Feel the difference between being in the center of your greenhouse and standing against one of its walls. Feel the changes as the days get longer in spring and shorter in fall. Everything is changing, and every minute something is happening. A cloud maneuvers in front of the sun and the temperature drops. Water the plants, and it can quickly feel steamy and tropical ... or cool and clammy. Each cloud, storm, hot spell, or cold spell is part of this inside environment.

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Walk up to a flower and look at it with a magnifying glass. Watch a bug go about its life for three whole minutes. Try to do this without feeling that this bug is the "enemy." Perhaps it isn't. Take a deep breath. Ready? Let's get into it.

The basic principle of greenhouse gardening is as old and uncomplicated as the practice of placing a glass lantern over a plant to protect it from the elements. I can imagine the delight of some farmer, back in time, when the idea of protecting a plant with lantern glass came to him. How pleased he must have been when he came out after a frosty night to find the plant still alive! The glass created a totally new environment within its walls, extending the productive life of the plant. It's like creating an earth within an earth or an ecology within an ecology.

The simplicity of light and glass creates a wonderful micro-system of incredible possibilities. For instance, greenhouse gardeners in cold climates who utilize solar heat are elated by the simplicity of warming both their house and plants by using the same light that grows their plants. But these wonderful possibilities can't be realized without you — that would be like having an orchestra without a conductor.

So what do you need to turn a sunspace into a tropical jungle full of blooms, fragrance, fruit, salad greens, herbs, and generally cool plants? There is a lot you can put into a greenhouse besides just plants. In this chapter and the next, we will look at how to optimize the greenhouse environment's efficiency and productivity. These chapters address only the basics of interior and exterior greenhouse design and are meant to help steer you in the right direction. If you hunger for more information on the subject, refer to a specific greenhouse design and construction book in your bookstore or the library.

Before you get started with any greenhouse construction project, check into the local regulations in terms of permits, zoning, setbacks, potential underground plumbing and electrical lines, and more. Local regulations may also require a certain type of foundation. Greenhouses attached to a home may have even stricter requirements. In some jurisdictions, freestanding hobby greenhouses are considered storage sheds and fly under the radar of strict regulations. Size may also be an issue with local regulations, and some people have avoided the legal radar by keeping their greenhouse below a certain size requirement.

Another consideration is to decide whether you want to build the greenhouse from scratch or go with a kit greenhouse. Read on for more information on both.

BEGIN WITH A GOOD FOUNDATION

A foundation is what you set your greenhouse or greenhouse kit upon. It is usually built of wood timbers (such as four-by-fours or larger), concrete, or concrete block. The greenhouse is then anchored to the foundation. The easiest way to have an awful time building a greenhouse is to fail to make your foundation square. To make it truly square, you can cross-measure the foundation from far corner to far corner. To check whether you are building it square, measure the distance between the northeast and southwest corners. Then measure the northwest to the southeast corner. If your foundation is square, the two measurements should be exactly the same; if they are not, make some adjustments.

Except for walkways, I don't recommend pouring a whole concrete slab for the greenhouse floor because it inhibits your future growing options. If you already have a slab, don't worry — there are things you can do to make the best of it. (See a more thorough discussion about floors in the next chapter and about growing in containers throughout the book.) Having a direct soil connection, however, enables you to plant directly in a ground-connected bed. This is an advantage for growing larger plants. It may also solve many drainage problems. Often, you can build your greenhouse directly on the existing soil and garden on that soil (usually with some added amendments). But first, be sure to check the soil for poor drainage, nutrient deficiencies, or other soil problems at your location. If there are problems with the existing soil, you should consider removing at least 1 foot (0.3 m) of soil where the greenhouse will sit and replacing it with imported, well-drained rich topsoil. If drainage is extremely poor, consider adding some drainage tiles or other drainage system a few feet beneath the soil surface.

A good growing greenhouse environment is determined by both the building's exterior structural design and the interior design. If this has been done right, then you are ready to become the conductor. The sun and plants know exactly what to do and just need a little coaxing and rhythm on your part to make your greenhouse an effective, productive place for year-round growing.

Designing and Building a New Greenhouse

So what do you need to turn a sunspace into a tropical jungle full of blooms, fragrance, fruit, salad greens, herbs, and generally cool plants? There is a lot you can put into a greenhouse besides just plants. In this chapter and the next, we will look at how to optimize the greenhouse environment's efficiency and productivity. These chapters address only the basics of interior and exterior greenhouse design and are meant to help steer you in the right direction. If you hunger for more information on the subject, refer to a specific greenhouse design and construction book in your bookstore or the library.

For those who are unclear about it, drainage is a function of how fast water percolates into the soil. If a small amount of water on the ground remains in a puddle for many hours then you may have a drainage problem. It is usually a result of heavy clay soil. You may want to consult some experts about how to improve the drainage and how to construct a drainage system. Your local county extension agent or other soils expert would be a good place to start if you have questions. Keep in mind that it is always easier to import soil and plan for drainage before you build your greenhouse. If your soil is in good shape and drains well, then you can proceed with construction.

Finally, consider insulating the perimeter of your foundation with 1- to 2-inch (2.5- to 8 cm)-thick rigid Styrofoam board placed vertically, 2 feet (0.3–0.6 m) deep, against the outside of the foundation. Doing so will help prevent the soil from cooling down in winter, thereby reducing your heating requirements. See the discussion later in this chapter on solar heating (pages 4, 50).

GLAZING

Glazing is the "skin" of the greenhouse, the feature that lets the light into the space. Glazing usually consists of glass or plastic sheets attached to the frame. Usually, the most expensive component of any greenhouse is its glazing material. The better the glazing, the more expensive the greenhouse. Most kit greenhouses use the double- or triple-thick polycarbonate plastic or glass glazings. I would suggest that you avoid single-pane or single-thick plastic glazing as it gets too hot in the summer and too cold in winter. Instead, go with double- or even triple-thick insulated glass or plastic. See more discussion about glazings later in this chapter. There are many cheap kits on the market that use plastic film glazings that usually won't last for more than a few years. I have seen these greenhouses ripped up in a strong wind. Sometimes you get what you pay for. Cheap can be expensive!

KIT FRAMES

A greenhouse kit offers a finished, workable design. It is also an easier solution for anyone who lacks building experience. That is not to say the experience won't have its frustrations. I have yet to see a kit that doesn't get even the better carpenters a bit frazzled. Still, most companies offer good technical assistance to help you through the difficult parts of the process. Some also have helpful videos. Plan on spending as much time setting up a level and square foundation for the greenhouse structure as you will to set up the kit greenhouse itself. This is true even if you are setting your greenhouse on wood timbers.

Having a quality frame and door are also important. This is hard to determine from photos. If you are considering the purchase of a particular kit, ask the seller if you can find a similar kit already set up in your vicinity that you could visit. If this is not possible, check to see whether the company has references whom you could call about the kit.

You will find that the manufacturers offer many different size options. It is rare that a greenhouse gardener doesn't eventually wish for more space. Purchase the largest greenhouse you can afford and/or have space for.

Most kits are constructed with either wood or aluminum frames. Wood has an inherent appeal but often requires some basic regular maintenance. Aluminum greenhouses can be either fragile or sturdy, depending upon the model. Aluminum lasts virtually forever, but it is a conductor of cold outside temperatures unless an effort has been made by the manufacturer to create "thermal breaks" in the structure. With a thermal break, the outside metal is not directly connected to the inner metal structure, which keeps the inside a bit warmer.

Solar Heating for Kit Greenhouses

Speaking of warmth, many people wonder if their kit greenhouse is solar heated. I have yet to see one marketed as such. You can, however, retrofit the kit greenhouse to be more energy efficient even to the point of not requiring a heater! This requires that you insulate the north wall, insulate the foundation with Styrofoam at least 1 foot (0.3 m) deep; use double- or triple-thick insulated glazing; seal every nook and cranny to prevent air leaks; make sure the vents and doors are weather-stripped and caulked; add some thermal storage such as drums filled with water; have a proper orientation with the glazing facing south; and possibly even install a night curtain for extremely cold climates. See the section later in this chapter titled "Solar-Greenhouse Heating Checklist" for further details on these retrofits.

Kit Options

Some kits are designed for attaching to a structure such as a house or garage. If you can attach your greenhouse to the south side of a structure, you can take full advantage of possible solar heating for both the greenhouse and the attached structure. Also, having a greenhouse attached or even close to your home insures you'll enjoy and take better care of the greenhouse than if it is way out in the yard. Still, having a greenhouse out in the yard is better than not having a greenhouse at all.

You may also be presented with venting and paint options. I would usually recommend the most venting possible unless you live in a place with cool summers. Many manu- facturers offer custom painting of the framing structure. Painting is a matter of personal preference, but keep in mind that white reflects the most light and seems to wear the longest.

The Company's Reputation

Finally, always check into the integrity of the company from which you are thinking about purchasing the kit. Here are some good questions to ask a potential kit seller. How long have they been in business? How many kits have they sold? What is their warranty? What technical help do they provide, and can you call them on weekends when you are liable to run into trouble setting it up? Most companies are rarely available on weekends. Ask if you can look at the manual to see if it is written in a simple manner. Does the company have a toll-free number? Does the kit require any special tools? Can you get a custom size? How is the greenhouse shipped and packaged? What if the kit arrives damaged? Do they provide any other free options? Many companies offer free growing books, thermometers, potting benches, fans, or other goodies as enticements to purchase their kit.

A greenhouse can be a big investment. You should feel comfortable with the company you choose to go with, so don't be afraid to ask questions!

GREENHOUSE CONSTRUCTION: GOING IT ALONE

Building a greenhouse from scratch may be a good option if you have some construction experience. Although building one yourself is usually cheaper than going with a kit-type greenhouse, it may not be that much cheaper. For some people, it might be worth spending a few extra dollars on a kit to avoid the added frustration of starting from scratch. For others, building things from scratch is a fun challenge and a joy that should never be denied.

First, you must come up with a design. Fortunately, a greenhouse is a relatively simple structure to build. The only things that distinguish a greenhouse from regular home construction are the glazing and the method of attaching this glass or plastic material properly. This is also a substantial part of the cost of building a greenhouse. Always shop around when considering a glazing purchase as you will find a wide variation in prices as well as shipping costs (be sure to read more about glazings later in this chapter).

Before you start your design process, be sure to read some books on the subject. Unfortunately, some of the best books on the subject of home greenhouse design are out of print. Two of my favorite out-of-print books are The Food and Heat Producing Solar Greenhouse, by Bill Yanda and Rick Fisher, and The Homeowner's Complete Handbook for Add-On Solar Greenhouses and Sunspaces: Planning, Design, Construction, by Andrew M. Shapiro. Still, these out-of-print books can be acquired if you check the library and used-book stores. There are also many on-line Internet services dedicated to searching for out-of-print books.

Sometimes you can find simple plans for constructing greenhouses in greenhouse supply catalogs, state energy conservation offices, or even through your local county agricultural extension office.

If you don't build it yourself or go with a kit, you can always hire out the design and construction of the greenhouse for your home at an increased price. For those who don't want the hassle of construction, this may be worth every penny. Look for someone who has some experience with a greenhouse. Still, you should do as much reading as possible so that you can be an active participant in the design process. It will be your greenhouse, and you need to have it fit your needs. Sometimes designers see themselves as creating a piece of art for you and have the disturbing attitude that you shouldn't be telling them what you want in If you don't build it yourself or go with a kit, you can always hire out the design and construction of the greenhouse for your home at an increased price. For those who don't want the hassle of construction, this may be worth every penny. Look for someone who has some experience with a greenhouse. Still, you should do as much reading as possible so that you can be an active participant in the design process. It will be your greenhouse, and you need to have it fit your needs. Sometimes designers see themselves as creating a piece of art for you and have the disturbing attitude that you shouldn't be telling them what you want in their creation. Avoid these types of architects and designers. This is the time to be sure to assert and communicate exactly what you want in a greenhouse — both structurally and with the interior design. If you don't build it yourself or go with a kit, you can always hire out the design and construction of the greenhouse for your home at an increased price. For those who don't want the hassle of construction, this may be worth every penny. Look for someone who has some experience with a greenhouse. Still, you should do as much reading as possible so that you can be an active participant in the design process. It will be your greenhouse, and you need to have it fit your needs. Sometimes designers see themselves as creating a piece of art for you and have the disturbing attitude that you shouldn't be telling them what you want in their creation. Avoid these types of architects and designers. This is the time to be sure to assert and communicate exactly what you want in a greenhouse — both structurally and with the interior design.

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Excerpted from Greenhouse Gardener's Companion by Shane Smith, Marjorie C. Leggitt. Copyright © 2000 Shane Smith. Excerpted by permission of Fulcrum Publishing.
All rights reserved. No part of this excerpt may be reproduced or reprinted without permission in writing from the publisher.
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