There is no better way to increase the range of plants you are able to grow than with a greenhouse. A greenhouse creates ideal conditions for a range of fruit and vegetables and prolongs the growing season long after summer has left us for another year.
Greenhouses are used for growing plants and flowers of all types. Even in the most difficult of climates, greenhouses allow for food and plant production. From the simplest concept of enclosing plants to shield them from the elements to elaborate structures enclosing entire environments, greenhouses are becoming an essential part of the future of agriculture.
History Of Greenhouses
- In 30 A.D., a greenhouse was built for the Roman Emperor Tiberius. It was constructed of thin, translucent sheets of mica. Called a specularium, this first known greenhouse was used to grow cucumbers all year round.
- In 1599, French botonist Jules Charles designed a greenhouse that more closely resembles in construction the modern greenhouse. Built in Holland, the greenhouse was intended for the growing and study of medicinal plants.
- Greenhouses became popular in France in the seventeenth century. They were used to grow orange trees and were called orangeries.
- It was during the Victorian era in Britain that the greenhouse became more commonplace. Their primary use was for citrus trees and exotic flowers.
- It wasn’t until 1948, in America, that the greenhouse was considered a viable option for commercial food production. This was largely due to the production of polyethylene, a type of inexpensive plastic that was used for the greenhouse cover.
The greenhouse is a microenvironment, closed and self-sustaining. The interior of a properly functioning greenhouse is unaffected by outside weather conditions. This makes it ideal for production of seasonal foods, flowers and plants that require specific growing conditions. It also makes it an excellent option for housing hydroponic gardens.
The greenhouse functions as an agricultural system. Within the system are subsystems: irrigation, containers or beds for plants, heating and cooling. By enclosing these systems the greenhouse acts as a kind of farm, allowing plant production to take place without the interference of outside influences such as indigenous soil content, adverse weather conditions and pests.
The smallest greenhouses are terrariums. These miniature greenhouses date back to the ancient Greeks. They celebrated the cycle of life and death by planting seeds in a pot, letting them germinate for eight days, then sealing the pots and tossing them into the sea.
The largest greenhouse is the Eden Project, located in Cornwall, England. Within the Eden Project visitors can stroll through rain forests, flower gardens, crop lands and landscapes that reflect the biodiversity of the planet Earth. The intent is to raise awareness of contemporary environmental issues and search for solutions to those issues.
The Eden Project covers 720 yards; that’s the length of nearly eight American football fields. It stands 165 feet tall and measures 330 feet wide. The Eden Project is made up of connected geodesic domes, each covered in ethylenetetrafluoroethylene, a kind of cling film or plastic wrap.
Whether it’s a tiny terrarium or a structure as large as the Eden Project, the greenhouse continues to advance in efficiency and use. New materials, new agricultural concerns and increasing interest in self-sustaining lifestyles will make the greenhouse a prominent feature in the continuing trend toward greener living.
Significance Of Greenhouses
Because the environment can be controlled, the greenhouse is ideal for cultivating plants that may not otherwise grow in certain areas or under certain conditions. For commercial growers, this greatly expands the potential for crop production and possibly lowers the costs of growing food. This savings would be passed onto the consumer. The drawbacks are the initial start-up costs of large-scale greenhouse farming and the possible disruption of localized eco-systems.
For the urban family, having even a small greenhouse can mean having healthy, pesticide free fruits and vegetables year round. Residential greenhouses can be detached or designed as an extension of the family home.
Temperature in Greenhouses
- How a greenhouse is to be used determines what level of temperature is needed.
For tropical and exotic plants, a hot greenhouse, or hot house, is needed. The temperature is kept higher, at least 65 degrees F. For plants that require higher temperatures, temperatures can reach as high as 80 degrees.
- The warm greenhouse is kept at 56 to 60 degrees. Most vegetables and garden flowers will grow within this temperature range within the closed environment.
- The cool greenhouse, kept at 45 degrees, is used for starting seedlings or growing plants that require cooler temperatures such as snow peas and spinach.
Common Greenhouse Features
The materials used for greenhouse covers vary. Glass allows for 100 percent light transmission and is inexpensive. It is vulnerable to damage, though. This makes it less desirable for both commercial and residential use.
Acrylic is more expensive, but it is lighter than glass and less susceptible to damage. It’s easily cut and shaped, making it a good material for the do-it-yourself builder. There is a slight reduction in light transmission compared to glass.
Polyethylene film is cheap and easy to work with, but it lacks durability. For smaller or portable greenhouses, polyethylene may be a practical choice. For the permanent structure, acrylic or glass is more suitable.
How To Pick The Right Greenhouse For You
Modern greenhouses can be found in every shape and size to fit even a novice gardener budget and needs. The construction of modern greenhouses has gotten so easy that even the novice do-it-yourselfer should have no problems.Although one normally associates greenhouses and frames with propagation, which may seem a little daunting and time consuming to a new gardener, there are other, more immediate benefits to owning a greenhouse or frame. So how do you choose a greenhouse type?
Identify your greenhouse needs. The most obvious use of your own greenhouse is that the growing season is extended beyond the first frosts of winter and the last frosts of spring. A greenhouse is particularly useful if you are tempted by the delights on display at the garden center early in the year, which are too vulnerable to be put out in the garden until the risk of frost has passed.
Consider the advantages of a wooden greenhouse.
Wood is the traditional material for greenhouse structures and is undeniably very attractive, whether painted or stained, rendering the greenhouse not only a useful addition to the garden, but a striking visual feature in its own right. Hardwoods, for example oak, teak, or cedar, although expensive, are the optimum choices, as they require minimal attention. Softwoods should be pressure treated with preservative, and will need regular painting or retreating with preservative.
Choose a metal greenhouse.
Aluminum has become the most popular structural material for greenhouses. It is less expensive than a hardwood greenhouse, easy to maintain, and its narrow glazing bars admit more light than wider wooden ones. It does not retain heat at night quite as well as a wooden greenhouse and is not generally considered as attractive, but for most gardeners, the advantages of cost and ease of maintenance more than compensate for these slight drawbacks. Both plastic-coated galvanized steel and galvanized iron houses will need checking regularly for rust. If rust develops they can require a certain amount of treatment and repainting.
Choose a glass greenhouse.
Glass is not only the most traditional glazing material for greenhouses, it is also the most effective. It is easier to clean and shade than plastic. It also retains heat well and conducts light better. However, it is not the most appropriate choice if the greenhouse is close to a play area or road, as it is obviously more prone to breaking than plastic.
Select a plastic greenhouse.
Plastic glazing is not as durable as glass, yet is often more expensive. It discolors easily and tends to become scratched over time. This is not only unsightly, but dramatically reduces the amount of light passing through the glazing. Plastic will generally need replacing over time. Polycarbonate has better insulating properties and is almost unbreakable, making it a good choice for greenhouses close to roads and play areas. However it is expensive, easily scratched and prone to discoloring.
A Guide To Choosing A Greenhouse Site
Ok, so you’re keen to get stuck in and start growing those 5 different varieties of tomatoes, first of all check to see if you actually have a suitable site for your greenhouse. You’ll need somewhere that will receive plenty of sunlight and is not completely obscured by the shade of trees or houses.
An ideal site will allow the greenhouse to be positioned with the long side facing south; not essential but this will allow for maximum sunlight and warmth. If possible, pick a site that will also allow for maximum sunlight during the autumn and spring when the sun is lower in the sky. Take into account nearby buildings and trees which may obscure the sun at certain times of year.
The site will need to be reasonably level and not prone to flooding. Don’t worry if the soil is poor as all greenhouse gardening can be carried out using grow-bags and containers.
Benefits of greenhouses
Growing from Seed
You can use a greenhouse to grow tender plants from seed. Some plants can thrive outdoors, but only once they have grown sufficiently or the weather has become warm enough. Plant the seeds in soil, compost or another suitable growing medium and keep the seedlings in the greenhouse until they are ready to be planted outdoors.
You can use a greenhouse to grow plants for winter use. Grow flowers and decorative plants to brighten up your home, or plant vegetables so you can have fresh produce in the winter months. Grow tomatoes, peas and beans in tubs, and plant root vegetables in boxes under the benches to save space.
Exotic Flowers and Plants
You can use a greenhouse to grow exotic flowers that couldn’t otherwise survive in your local climate. Tropical plants like bromeliads and some orchids prefer a hot, moist environment, such as you can create in a heated greenhouse.
Holding Over Plants
Sometimes you will want to remove plants from your garden and replace them, perhaps when their growing season is over and they have stopped flowering. Instead of dumping them, you can hold them over in your greenhouse and use them as parent plants, allowing them to set seed (become pollinated and develop seed pods) so that you can harvest the seed to plant next year.
Cuttings are small sections taken from a parent plant and grown into separate plants. Cuttings can be vulnerable to changes in the weather, so it’s a good idea to grow them indoors. You can find growing medium, a gel containing special nutrients and rooting hormones that encourage the cutting to take root. When it’s established, transfer it to a pot of soil, and later bring it out of the greenhouse to plant in your garden.
A greenhouse allows you closer control over plant pollination. You can create your own cross-bred flowers by carefully selecting the parent flowers for desirable traits, and then pollinating them by transferring pollen between plants yourself. You will need to keep insects out of your greenhouse to ensure that only the cross-breeds you want are created.
Basic types of domestic greenhouse
There are two basic types of greenhouse.
- Lean too – these have 3 sides and are designed to be positioned next to a wall or other vertical surface.
- Free standing – the conventional 4 sided greenhouse
- Other types include hexagonal shaped greenhouses, mini greenhouses and plastic poly tunnels.
The most popular greenhouses are freestanding and are made from aluminium and glass.
- Aluminium doesn’t rust and will last for many years with no maintenance.
- Timber, although it looks stunning, will eventually need repainting or re-oiling.
- Glass offers by far the best choice for the windows unless you have young children, in which case you might want to consider polycarbonate glazing for safety.
- Polyethylene (as used on the poly tunnel type greenhouses) can tear easily and won’t stand up to strong winds particularly well, however they are cheaper and safer than glass.
What size greenhouse?
The size of greenhouse you choose depends on the available space and how much produce you want to grow. Greenhouse gardening is addictive, so get the largest you can because it wont be long before you’ve filled it with plants and vegetables. You may also need room for a potting bench or staging. A common size is 6×4 foot, but this often proves too small for the keen gardener.
If you just don’t have the space for a proper walk in greenhouse, there are other options available. Two Wests have a wide range of patio greenhouses which are ideal for the smaller garden.
During the summer, temperatures can become too extreme for the plants so the greenhouse will need ventilation. The more ventilation options the better. Two helpful aids to keeping the temperature correct are liquid shading and automatic window openers. Liquid shading (whitewash) is painted onto the outside of the greenhouse and reduces the effect of the suns rays. Automatic openers (auto vents) attach to the ventilation windows of the greenhouse and automatically operate when the temperature reaches a certain level.
Greenhouse humidity and watering
A good way to create a humid environment is to utilise a shingle floor inside the greenhouse. Lay an anti-weed membrane and cover with either pea shingle or the slightly larger 20mm beach shingle. During hot weather, sprinkle the shingle with water. The evaporating moisture will create the humid environment many plants and vegetables favour.
There are a few challenges when looking for the ideal Greenhouse
- Type of material
If you plan well you should think of
- Irrigation and distance form water
- Heating if in cold weather
- Protecting from animal pests