The Greenhouse Effect (Is a Greenhouse a Good Idea for Your Garden?)
Greenhouses can be beautiful and useful structures for a gardener. If you have ever wondered if it would be worth it to construct or buy one for your garden, we have some thoughts to help you sort out the pros and cons.
What is the Purpose of a Greenhouse?
Greenhouses serve as a shield between nature and what you are growing, and thus allow growing seasons to be extended as well as possibly improved. They provide shelter from excess cold or heat as well as pests. While we use it tongue in cheek, the term “greenhouse effect” in regard to our earth is a more complex and serious consideration for our global environment, but for the home gardener the effect of a greenhouse on plants can be very positive. The idea behind a certain type of greenhouse is to create a place to keep heat in. The structure impedes the flow of thermal energy out, and the sunlight that passes through the transparent “walls” of a greenhouse heats up the ground in the greenhouse which radiates warmth and heats the air. Or, if too much heat is a problem, a greenhouse can help you create or regulate a more temperate environment for plants by adding a cooling mechanism.
Types of Greenhouses
What type of greenhouse you need depends on where you live and what you want to grow. Greenhouses are categorized in a variety of ways.
Temperature – The spectrum of structures based on the environmental temperature needs include the following types:
Cold Houses – (Temperature: Falls below freezing) Provide protection for plants, but temperatures still can get below freezing because this type of greenhouse has no additional heat source installed. The purpose of cold houses is to extend growing season in the spring by allowing starting crops earlier and in the fall by allowing crops to grow longer.
Cool Houses – (Temperature: 45-50F) This type of greenhouse will maintain temperatures above freezing so that plants that die from extreme cold can survive.
Warm Houses – (Temperature: 55F) Allows for a broader range of plants to survive cold winters.
Hot Houses – (Temperature: above 60F) Hot greenhouses are used to maintain tropical plants. In order to heat they require supplemental heat.
Within each of these general types, there are many other considerations. There are very simple greenhouses and highly complex ones. The more technology that is involved the greater the ability to exactly control the growing conditions, from temperature to water and moisture levels. Greenhouses can also be constructed simply to minimize direct sunlight (a shade greenhouse) and not have walls, or a screen-only structure to keep out insects.
Design –Greenhouses can also be evaluated based on the design style. This is the fun part. Some of the traditional types of greenhouse “architecture” include A-Frame, Dome, Gothic (arched), Lean-To (can even be designed to use the wall of a home or garage as one side), and Quonset.
Materials – For the residential gardener, the choices are almost unlimited. Price will likely drive some of the decision making on this, as will aesthetic considerations and your purpose. All have advantages and disadvantages.
Support/Framework Options: wood (rots easily), aluminum, iron and plastic. Some have curved eaves; others have flat eaves.
Covering Options: glass (most expensive but lasts longest, also beautiful), fiberglass (can become discolored), plastic (cheap but effective), double-layered polyethylene (must replace every 2-3 years), PVC, acrylic (very expensive).
Environmental Control Options – Budget will impact what you are able to do in this area. Automatic controls are ideal in a greenhouse, but obviously will be more expensive. Your options for heating equipment include a simple space heater, forced-air heat, radiant heat, steam or hot-water systems, as well as soil heating pipes underneath plants. Automatic watering systems for larger greenhouses are nice. Planning for ventilation is also essential for the health of your plants.
Some Pros and Cons
After immersing yourself in the overwhelming amount of information about the vast number of choices and decisions about what type of greenhouse you could build, let’s revisit what some of the reasons you would want to do this – or not.
The Benefits of a Greenhouse:
- Fresh greens, vegetable and fruit
- Transplant availability and success
- Fresh cut flowers all year long
- A warm place to go in the middle of a cold, gray winter
- Ability to grow things you wouldn’t otherwise be able to grow (exotic flowers, tropical fruit)
- No more battles with squirrels and insects
- Do more of what you love to do, longer Add beauty and visual appeal to a landscape
The Disadvantages of a Greenhouse:
- Can be expensive to build
- Can be expensive to heat
- Requires constant monitoring, maintenance and care
- Could increase electrical and water bills
- May detract from aesthetic appeal of a garden
Your greenhouse garden can be constructed cheaply or expensively, it can be made of glass or plastic, it can look like an adorable glass cottage or simply serve a practical purpose. Ultimately, the decision to get a greenhouse will be based on whether you believe the effect of having a greenhouse will be one that will enhance your life or detract from it. If you would like more information about greenhouse designs, this is a good place to start: http://www.houzz.com/greenhouse.