Like to Garden? Consider a Greenhouse!

Do you love plants and gardening? Then you may want to consider a personal-sized greenhouse to extend your green thumb endeavors.

Greenhouses come in many sizes - the greenhouse you consider might be an 18 by 24 foot (five by seven meter) unit in your backyard. A greenhouse this size will hold many plants, which can require a good bit of time on a fairly regular basis. The size of the greenhouse is a factor in how much of a time investment you will need to make, but ways of automating some of the care, as well as the kind of plants you grow, will all influence the amount of ongoing labor that will be involved in your unit. But before we get to that, let’s back up and look at the overall picture.

The Greenhouse Idea - Planting the Seed

If the idea of a greenhouse appeals to you, then taking inventory of your lifestyle and available time is a good place to begin. Do you have time each day to relax as you care for your greenhouse? How much time do you realistically have available? Do you travel out of town overnight frequently or for extended periods of time? If you do, do you have someone in the family, or a friend, who will care for the greenhouse and plants while you are gone? Remember, the greenhouse and plants do not go on hold while you’re gone! There are automated systems that can be put in place, but a human is usually needed to oversee the goings-on. If your time is limited or you travel frequently, you might want to focus on a downsize greenhouse and a growing system that will require no more than a couple hours a day.

You can really dream and get creative as you plan! Greenhouse growing can be a fun and fruitful family activity, or a great way for friends to socialize and relax together. As you plan your greenhouse, you may want to allow enough room for yourself and another person or two. Some folks like to include enough room to set up a table and chairs where they can enjoy a cup of tea or coffee. Others like some patio chairs to relax and read in, still others like to set up a pond or even a small waterfall to enhance their daily greenhouse experience. Of course, this means leaving some open space in your greenhouse so that you can set up the extras that will help you enjoy the special environment you are maintaining. Taking relaxation one step further, some folks even install a hot tub in the greenhouse! On a more practical note, you may want to incorporate a workbench and a sink with a drain. Already, this little greenhouse you initially thought about needs to be bigger! Make a list of what you want to do in your greenhouse. Have a brainstorming session and have a friend or two look at the list and see if other possibilities arise.

Dealing with Specifics and Planning Ahead

When your list is finished, you might discover that your list is longer than what your budget will conveniently accommodate. If that is the case, you’re going to need to do some trimming. Keep in mind the most important rule of thumb: it is easier to add internal features to the greenhouse over time, than to add space to the greenhouse once it is in place. As an example, the environmental control system in a greenhouse is generally designed specifically for that size unit. As a result, making the greenhouse larger after it is first built makes the original environmental equipment obsolete because of its lack of increased capacity. Many people also find that the greenhouse they planned isn’t large enough once it’s erected and they have filled it and are using it. Both hobby greenhouse owners as well as commercial greenhouse growers complain that they didn’t start with a big enough greenhouse. So be sure to make the basic greenhouse larger than you think you’ll want if you can in any way work it into the budget.

Now, let’s move on to planning the location to erect the greenhouse. A suitable greenhouse location will include a spot where the sun reaches most of the day. An open spot is needed where the sky is clearly visible to the east, south and west if you’re in the Northern Hemisphere. If you’re in the Southern Hemisphere, you want the northern sky rather than the southern sky. Anything short of this will reduce the maximum plant growth in your greenhouse. A little shade is tolerable because you’re not building your backyard greenhouse to maximize commercial production. But you need enough light to have a reasonable level of success.

The greenhouse should be level from side to side, so a level site is needed. You need to create a natural flow for drainage within the greenhouse. To achieve this, the floor should be sloped at least 1% toward the winter sun end of the building. This slight slope is not noticeable as you move around the greenhouse, but it will facilitate the drainage of many of the plant production kits that you may later decide to install.

Yet another factor in determining the location of your greenhouse is access to the utilities you will need - electricity, water and fuel to operate the environmental management equipment and to feed the plants. Generally speaking, the farther away from your residence the greenhouse is located the more it will cost to run those utilities to the site. If you want or need to run any drainage from the greenhouse into the residential sewage system, the location of the greenhouse will impact the cost of the line, as well.

To avoid unnecessary costs in the future, plan ahead so that you need to run the utilities to the site only once. Just like when you plan the size of the greenhouse, it is best to size things beyond what you think you will need. Over-size things to at least half again what you anticipate needing as long as doing it doesn’t cost more than twice as much. As you use your greenhouse, you’ll inevitably come up with some new ideas and projects you will want to try in your greenhouse. If you’ve planned ahead and installed utilities that allow for growth, incorporating those ideas will be a lot more doable and less expensive.

As an example, if you think you may someday want to run artificial lighting (high intensity discharge lighting) in your greenhouse, it makes sense to run a big enough electrical service to the greenhouse when you first install the utilities to handle the future need. Supplemental light uses a lot of electricity! If you are preparing for the possibility of lights, consider supplying enough power to your greenhouse to run 16 to 17 watts per square foot (or160 to 175 watts per square meter) of greenhouse area.

Water is a critical component in greenhouse growing. The water quality is going to be very important to the plants in the greenhouse. You should have the water tested before you decide to put in a greenhouse. Most water can be used, and possible shortcomings in water composition can often be managed. But if your water needs some treatment to be useable, or is not useable at all, that is something you need to know before you commit to your greenhouse project. Since an alternate source of water is usually not available, you’re going to need to take the steps necessary to make the water you have suitable for use. It could cost a few hundred to a few thousand dollars to treat the water to make it usable in the greenhouse. If you have a water softener in your home, do not use softened water in the greenhouse! Tap into the water line before it goes through the softener - directly from the unsoftened, incoming supply. The calcium and magnesium removed from the water by the water softener is good for the plants. The sodium introduced to the water, however, can only be tolerated up to a limit of about 75 parts per million (ppm). In most water softener applications, the sodium in the softened water will be higher than 75 ppm or the water softener probably would not have been needed in the first place.

Yet another area to deal with as you plan your greenhouse is local zoning regulations. In some areas, you will need to abide by zoning restrictions. Because zoning regulations vary widely from area to area we suggest you check with your local zoning authorities early in your planning.

Let’s move on. You’ve done the basics. You know you have zoning approval, your water has been tested and it’s useable and you have the perfect spot for your greenhouse. How do you know which direction to orient the building? The preferable orientation for the greenhouse is a north-south direction going along the length of the greenhouse. This is to maximize the amount of natural light received by the contents of the greenhouse throughout the year. Greenhouses built for bedding plants are often oriented the other way and many books will tell you to orient greenhouses the other way, but the North to South orientation is preferable to maximize light. You can vary that orientation up to 12 degrees to the east or west if that will help you line it up with other things on your property. That amount of deviation will not significantly affect light exposure and the productivity of the greenhouse.

So much for the technical and the planning. Now, on to the rewards... the time spent in the greenhouse will include culturing, watering and caring for plants. It will also be a time away from the cares and demands of the rest of your life. The environment in the greenhouse can provide some quietness and calm in the midst of our fast paced, stressful lifestyles.

Plants are dependent upon us, but they also give to us. Meeting their simple needs is usually fulfilling rather than a hassle to us. Beauty to the eye, and delicious, fresh edible parts are just some of the rewards that plants share with us.

Plant care has so many beneficial effects for humans that Horticultural Therapy is an entire discipline. It is well known that having people with certain problems work with and care for plants has beneficial influences for them. Benefits from caring for plants can be enjoyed by the rest of us also.

Nuts and Bolts

The most obvious part of the greenhouse environment is the structure. It is the necessary packaging that provides light penetration at the same time that it provides isolation from the outside elements. Environmental controls and feeding systems are what make the enjoyable atmosphere when we’re in our greenhouses, plus they keep the plants growing even in our absence. Heaters, fans, evaporative coolers, feed systems and environmental controllers are all system components that are important. Together, they can cost more than the greenhouse structure itself. Some greenhouse purchasers have the unfortunate experience of purchasing the structure, then discovering that they need far more in order to make the greenhouse work. For this reason, you should take a systems approach when planning and buying a greenhouse. Make sure all the ancillary equipment you need, like environmental control hardware, is included in your greenhouse purchase. Pay attention to the actual components of your structure, from bottom to top.

Even the structure itself needs some attention in the planning stages. The quality of the structural components will determine how well and how long the greenhouse will stand. Light weight aluminium, pvc plastic and fence-grade steel are sometimes used as greenhouse structural components. Structural steel will perform better and last longer. It may cost a little bit more than some of the alternatives, but it will outlast them and be more cost-effective in the long run.

Greenhouse coverings run the gamut from glass to polycarbonate to greenhouse polyethylene (heavy plastic sheeting). Glass and tempered glass greenhouses are the most expensive structures. Except for possible breakage, the cover will probably never need to be replaced. Double walled polycarbonate has a 12 to 15 year life. A double walled polyethylene greenhouse with an air space between the two poly layers is a relatively inexpensive cover with a limited life of an average of four years. Your budget, aesthetic considerations and possibly zoning restrictions will be considerations when making choices in this area.

Heat, Cold and Ventilation

Do you really need to put a heater into your hobby greenhouse? In most parts of the world, the answer is yes if the greenhouse is to be run and enjoyed all year. There’s not much insulation value in the covering material of the greenhouse – this is partly because the materials used must be designed to allow transfer of light into the greenhouse. Even when days are warm enough for people to enjoy the greenhouse environment, the nights may be cool enough that the plants would suffer or be damaged without a heater.

Air movement through the greenhouse is necessary for the proper growth of the plants. Air movement is used to provide cooling of the greenhouse environment. A system of vents can be used for greenhouse cooling, such as what are found in a naturally ventilated greenhouse, which is designed so that the placement of the vents will work to move air through the greenhouse. Air currents outside of the greenhouse greatly increase the airflow within the greenhouse. When greenhouse cooling is needed, how often is there air movement outside the greenhouse to help facilitate the inside cooling? In different parts of the world, the answer to this question can vary considerably. If there is good natural air movement in your area, does it occur in your back yard? Are there structures or trees that block or reduce air movement in the area of your greenhouse? If you use natural ventilation in your greenhouse, should you have manually operated vents or power vents? That depends upon whether you can be present in your greenhouse whenever the vents need to be adjusted. For most people, that means that power vents are the answer. However, natural venting, while less expensive, is not always the most consistent means of temperature control within the greenhouse, especially in locations where air currents are erratic.

The most consistent way to cool a greenhouse is with electrical exhaust fans and louvers or an evaporative cooler. The rate of air movement through the greenhouse is more directly controlled by the operation of the fan(s). This way, when outside air is still, greenhouse air movement can still be generated by the operation of the greenhouse fans.

An evaporative cooler can provide air into the greenhouse that is cooler than outside air. This is equipment that may be added to a greenhouse later if the initial costs get beyond the budget. Even if installation will take place in the future, it’s best to plan for it from the beginning so that the proper control equipment, utilities and space are already in place when it is added.

Evaporative coolers can more effectively reduce the temperatures in areas where the average relative humidity is lower than in areas of high relative humidity. Generally speaking, temperatures are higher in areas of low relative humidity than in areas of higher relative humidity. An example of this is the difference between the summer desert (low humidity/high temperatures) versus the high humidity but lower summer temperatures among the Great Lakes region. In areas where the evaporative cooler will lower the temperature five to seven degrees °F (three to four degrees C), that temperature reduction can keep the plants healthy for a significant additional time. In many areas of the world, some form of cooling is necessary if the greenhouse is to be operated year round. An evaporative cooling system will provide the most economical cooling in most applications. A more effective, but more expensive mist system is available but likely to be reserved for commercial growing in naturally ventilated greenhouses.

Environment control equipment costs can (and usually do) present a higher percentage of the overall cost of a small greenhouse system, as opposed to the percentage of the overall cost it can present in a larger greenhouse system. The equipment is essential for creating and maintaining the environment necessary for plant health. Once again, when the whole system – both the structure and the necessary components - is considered in one package, the overall size can be adjusted to the budget, yet yield a fully functional greenhouse. If a person gets just a greenhouse frame without the needed environmental equipment, he or she might find that installing the needed equipment is out of the current budget and more expensive than it would have been as part of a complete package. Remember, the whole idea of the greenhouse is to provide a stress free sanctuary where you can enjoy your horticultural hobby, not another source of stress! Planning wisely is the way to accomplish this.

Do You Have to Use Soil?

The answer is no. Of course, we all know that plants can grow in soil. But soilless plant growth can actually help avoid some difficult growing problems. Soilless greenhouse production developed when the use of soil treatment chemicals was banned and the cost of steaming the soil to prepare it became cost prohibitive. In a small system, soilless production is relatively easy and not expensive. Soil borne insects and diseases are not introduced to the greenhouse when sterile, soilless media are used.

If you need to start one step at a time, and can’t include the cost of a hydroponic or soilless system in your initial greenhouse investment, you can grow greenhouse plants in the ground during the first couple of years, assuming the soil is suitable for plant cultivation. Even if cost is not a factor, some people feel more comfortable growing in soil at the beginning of their greenhouse experience. (However, if your soil is not plant-friendly, then soilless media should be used.) After a few years, a combination of problems associated with the continual reuse of soil will usually encourage a transition to hydroponics or container organic systems.

Hydroponic production systems operate with the needed fertilizer ingredients dissolved in the water of the system. The fertilizer ingredients do not actively interact with the media in a purely hydroponic system. The media simply acts as a sponge for the fertilizer-rich water in the system, making the nutrients available to the plants.

Organic production systems involve microbial activity in the media. The microbes get their energy from the media and break it and supplied fertilizer sources down to simpler forms that can be absorbed by plants.

Although organic production can be done in the soil of the greenhouse, most people will find it easier to start with an organic soilless media mix. Organic fertilizer programs and supplies are available for these systems.

Several hobby production system kits are available for use in small greenhouses. You will probably want to choose one or more of them to produce a variety of plant types in your greenhouse. If the budget is tight by the time you reach this stage, you may want to get one or two systems and put off purchasing others until more funds are available. The systems are easy to add as you go along.

Small plants that reach maturity or harvest stage within a few weeks can be grown in an NFT (Nutrient Film Technique) system. Larger plants and plants that will be grown, cut and let re-grow will do better in the long run if they are grown in a media-based system. That media can range from an organic soilless mix to rockwool slabs to perlite in many types of containers or packaging.

You Did It Your Way!

Whether it’s flowers, bushes, trees, fruits, or vegetables, having your greenhouse and selecting your growing systems means that you grow things your own way. You experience the process. You’re part of the process. When doing this on a small scale, the entire growing experience need not consume more of your time than you can afford to give it. As you look around the plants thriving under your care, you feel you accomplished something and you enjoyed the path as you make the accomplishment.

Perhaps your goal is to grow plants for aesthetic enjoyment. Grow what you like, surprise yourself with new varieties, with colorful blooms in the off-season, and with mastering plant propagation and other techniques you may have wanted to explore. Perhaps you like the idea of growing your own food. This way you know it’s safe, because you know how it has been grown and what has and has not been used to grow it. Of course, taking this on this type of growing will involve some commitment of time and planning a production schedule. Producing your own fresh food during the winter or in some areas during a stretch of hot weather can be challenging. An overlapping schedule for long term plants like tomatoes and cucumbers will need to be planned.

Whatever you want to grow and however you grow it – if you plan and choose carefully, you will be sure to have a pleasant experience. The tips and information reviewed in this article are provided to help get you started in the selection process with a minimum of surprises and hopefully no disappointments. Check out suppliers carefully, make sure they have experience in a variety of systems and can discuss alternatives with you intelligently. Buy the best greenhouse structure you can, ask questions and invest now in what you can’t change later on – the size of your greenhouse structure, the quality and the basics. The rest are fun things to add as you grow in experience as you enjoy tending to your plants. Happy growing!

James W. Brown has been a horticulturist in the hydroponic industry for twenty five years. He has worked with hobby and commercial growers helping make them successful in their endeavors. He has a bachelors degree in horticulture from Macdonald College of McGill University and a masters degree with a major in Vegetable Crops from Cornell University. He has written construction manuals, conducts grower training workshops, assisted in developing interactive training cd-roms, and works with growers on a daily basis.