Plants For Your Greenhouse

Ok, you’ve put a lot of effort into planning and building (or installing) your greenhouse. You’ve got tabletops, benches, pots, shelves, cabinets, watering systems and a dozen tools to help. Now, you get to really enjoy what greenhouses are all about – plants!

The ‘green’ part of greenhouses is usually the most fun, since that’s why you get one in the first place. But here, too, you’ll want to do some planning and careful execution. That planning should start at the same time as that for the greenhouse itself. The structure and its contents should be well matched for optimal results.

Fortunately, you’ve got hundreds of choices.

Consider first where you live. Even in a greenhouse, the amount of sunlight per day throughout the year, humidity and temperature levels and other variables need to be accounted for.

Northern Idaho, for example, has long, dry summers. New Hampshire, even though it’s also in the northern latitudes and gets about the same amount of rain and sun, is much more humid. You can only control humidity to a certain level.

If you get plenty of sunlight in the summer and early fall, or can compensate with artificial lights, tomatoes love greenhouses. The high heat makes them grow great and, since they are easily injured by frost, they appreciate the protection in the Fall.

Some citrus fruits, like oranges and lemons, are nearly impossible to grow outdoors in certain locations. It’s simply too cold much of the year. But you can compensate in the greenhouse and actually grow your own.

Strawberries are another favorite for greenhouse gardeners. Commercial strawberries are expensive and many people have concerns about pesticides. You can grow your own and control costs and quell health concerns.

Radishes, onions, carrots, lettuce and spinach like cooler temperatures. They can really do well in a controlled environment like a greenhouse.

Then, of course, there are the traditional ‘hothouse’ flowers – orchids first and foremost. Orchids in the wild grow up higher because they benefit from the breezes. You can simulate that in the greenhouse with a simple fan and ventilation system.

Orchids can also be very expensive and growing your own can be a great way to save money and still have beautiful flowers. For the truly ambitious, there are dozens of competitions across the country for orchid growers. Be careful of getting bitten by the ‘orchid growers bug’, though. It can turn into an all-consuming hobby!

But lots of other flowers make great choices for greenhouses, too. Practically anything you would grow in an outdoor garden will do fine in a greenhouse, provided you have proper sunlight and shade control. Keep in mind, too, that some plants don’t do as well in pots unless they are large enough that the roots have plenty of room to spread.

Most bonsai are outdoor plants, though some benefit from the protection of a greenhouse in high winds and cold winters. Take care that the species you select is suitable for a high temperature, high sunlight and humid environment.

Sooner or later, though, it’s time to stop planning and start gardening. Enjoy!

Planning Your Greenhouse Water System

It’s obvious to say that greenhouse plants need water. But how they get it – and how much they need – will have a big influence on your level of effort in maintaining them.

Cacti, just as one obvious example, need barely any added water at all to survive. They are extremely efficient at retaining the water they receive through the roots. Most bonsai, on the other hand, can almost never be overwatered provided they have the proper soil for good drainage.

So, the first consideration in planning your greenhouse water systems is to decide what kind of plants you intend to have, now and later. This will help you determine whether you can be satisfied by bringing in a watering can once a day or whether you’ll want to go to the extreme of having an automatic watering system.

Automatic watering systems can be similar to soaker hoses lying in or on the soil that slowly leech water into the earth. Or, they can be overhead sprinkler types that either spray or mist water onto the plants. Again, the type you want will depend on the plants you intend to have.

An intermediate solution is to simply have a spigot or long hose from the house that allows you to water by hand more easily than using a watering can. In this solution, an internal spigot is preferable so you can keep the door to the greenhouse fully closed while watering.

Piping water to the greenhouse is no more difficult than running standard lawn-sprinkler type PVC pipe a few dozen yards. Unless you have a very large greenhouse, standard pipe will supply plenty of water for your needs. The pipes themselves, and the couplers and controls needed, are inexpensive. The major expense (or difficulty, if you do it yourself) is digging the trench.

Keep in mind when you plan any kind of overhead system that mists or sprays water that some of that moisture is bound to go to places other than the plants. Benches, floors and other greenhouse components should be able to withstand wet conditions without causing problems.

Excess moisture will inevitably end up on the walls and roof, no matter what kind of watering system you use, if your plants are anything other than cacti. Water evaporates from the soil surface and leaves, humid air enters when you open the door. You’ll want to plan for some kind of ventilation. You’ll also have to clean the walls and roof from time to time.

Ventilation can be a simple fan, plus a narrow gap around (at least part of) the roof. Cleaning mildew and other consequences of moisture in the air can be done using standard products, but it will be done less often if you plan your watering system not to accidentally spray anywhere other than the plants.

Allow 10-20% of your construction budget for your plumbing system. Even after the initial build-out, you’ll have to do maintenance from time to time. Pipes and hoses crack, especially in extreme temperature change conditions and valves eventually go bad.

Greenhouses Repairs and Maintenance

Like anything around the home, greenhouses will require maintenance and, from time to time, some repairs.

Since they are fairly well sealed, water (and therefore mildew) will build up on the walls. Even those with gaps under the roof line and venting fans still retain considerable moisture, and algae, mold and mildew will form on the surfaces.

Both for the sake of the plants, and your own health, that will need to be cleaned off from time to time. Fungi and mold that cling to walls don’t just stay there forming an unattractive appearance. They spread, over the walls and through the air onto plants and into your lungs. Not good.

Take a cloth or sponge and wipe the surfaces dry from time to time. If mildew has built up, it’s usually sufficient to use a commercial spray to get rid of it. Sometimes you need to work a little harder to get into the cracks with sponge and spray.

Floors, too, can accumulate unwanted compounds. Many greenhouse floors are wood, gravel or even just dirt. While they don’t need to be as clean as your house, any of those will require some treatment from time to time. Wood can accumulate slippery-when-wet mold, gravel allows weeds to grow through, and dirt can become mud. Even cement will need to be swept or cleaned periodically.

If you have a greenhouse roof made of certain plastics, you’ll find that over the course of a few years it may well darken or yellow. That change reduces the amount of light transmitted and ultimately leads to cracking. It will need to be replaced sooner or later.

Even ordinary glass can yellow over time and become brittle. As it does it transmits less light and is more likely to break from hail or accidental bumping. Though this will take much longer than most plastics, you should be prepared for the possible replacement cost after 7-10 years or so.

New polycarbonate panels are making their way into greenhouse construction. They transmit light well, have very good heat retention properties, and can last for decades. But the seal between panes can require repairs from time to time. Re-caulking is usually all that’s needed and can be carried out with a good scraper, a caulking gun and a lot of patience.

Incidentally, condensation within sandwiched polycarbonate panes, and between the panes, walls and other parts can also become covered with algae and mold. Be prepared to clean them, though it won’t be required as often as glass.

Ice build up, sharp temperature changes, falling branches and other events can require replacing a pane. A modular construction plan can make that easier and less expensive. Plan or select your design accordingly.

Of course, there’s repair and maintenance of watering systems, benches and table tops, and so forth, don’t forget. And you thought it would all be just gardening…

Planning Your Greenhouse Electrical System

It is possible to have a good greenhouse with no electricity. But your results will be improved and come easier if you install several systems and devices to help you.

There’s the basic outlet system, of course. Some greenhouses have supplies that rival a small house. And, for good reason – they are practically that! Even ignoring commercial greenhouses that sometimes run as large as 40 feet by 60 feet or more, a homeowner’s greenhouse could well be 10 feet by 20 feet.

With a structure that large, you’ll have plenty of room for a variety of plants – orchids, fruits and vegetables, Bonsai (which normally live outside, but some species need protection from harsh winters) and others. With all that room, and those plants, having electrical outlets can be a big help.

Electrical outlets will make it possible to plug in space heaters, to compensate for excessively low winter temperatures when you have long days of no sun. Or, you may want to have a fan in the summer to regulate heat and supply air flow. Orchids in the wild, for example, thrive up where there are breezes. And, of course, having lights installed is essential for working in the greenhouse after dark.

Apart from these very basic systems and devices, there are many specialized tools that can make your efforts easier and safer for the plants. Automatic watering systems are a big convenience and can be adjusted to supply just the right amount of water where and when needed. High speed drills, soil heating devices and a range of even more exotic aids all require electricity.

More advanced greenhouses may have a light control system, shades or shutters, that operate by sensing the amount of light and opening or closing down automatically. That requires electricity. Solar panel systems, while neat and helpful can’t always supply enough power to run larger devices.

You should plan for both 110V and 220V outlets, and enough amperage to cover the equivalent of two normal home bedrooms or more. Special-purpose outlets, conduit and other electrical components are available online or at the hardware store. If you don’t have the skills to install the electrical systems, and most gardeners don’t, an electrical contractor can obtain all the right parts for you.

Don’t skimp on the outlets. It’s annoying and unsafe to have an outlet 10 feet away when you need one at the base of your table. Be sure to order or insist on components and a supply that will more than cover your needs now and in the future. Creating an electrical system is pretty straight forward during construction. Modifying it later is difficult and costly.

Plan ahead and be prepared to devote 10-20% of your budget to the electrical system. The payoff in convenience and the health of your plants will more than compensate in the long run.

Carpentry Skills For Greenhouse Construction

Many people interested in having a greenhouse enjoy the prospect not only of using it, but of building it, too. Unless you purchase both the house and all its contents, you’ll have to have some carpentry skills.

Many greenhouses have wooden floors. Relatively simple to construct, they can be made with 2 x 4’s or 1 x 6’s attached in a grid onto 4 x 4’s that sit on the ground. Spaced a half-inch apart, that can allow drainage. Weeds that tend to grow between the slats can be kept under control with any commercial spray. Even the average do-it-yourself’er can easily make a good greenhouse floor in a day.

From that point, the skills level goes up a bit. Constructing greenhouse walls is a little tougher than it looks. Building a wall perpendicular to the floor isn’t too difficult these days, especially using laser levels. But proper bracing requires a well thought out plan. You’ll need a design and materials that can support a roof and stay sturdy for several years.

One way to develop that plan is either to buy one from any of the many sites online that offer greenhouse plans, or study a house under construction. The same principles apply. Either you’ll need regular-spaced 2 x 4’s (usually 16 inches apart) and/or a large number of L-braces (4 inches per leg or longer).

After you have the plans and/or the actual greenhouse built, the fun starts for those who prefer to exercise their carpentry skills on furniture.

Any moderate-sized or larger greenhouse will need one or more good tabletops. Many types are available for purchase, which is fine for those who want to go that route. Do-it-yourself’ers will enjoy making their own.

Here again you need to draw out what design you want before pulling out the hammer and nails or screws and drill-screwdriver. 4 x 4’s make excellent sturdy legs. Be sure to buy or cut ones that have perfectly perpendicular ends to support the top.

One excellent and simple design involves laying a flat top (say a series of 1 x 12’s with cross supports or a flat, sturdy piece of plywood) onto the legs. Nail or screw the top down onto the legs so you have something level and fairly sturdy. Then use some L-braces to increase the support in the horizontal direction.

Cap it by using plywood strips or 1 x 6’s perpendicular to the top. Connect them to both the legs and the top with L-braces. Rock solid and attractive. Stain when complete to keep moisture from corroding the table.

You can use the same method to build benches for holding rows of plants or to sit on. Or you can use a trio of 2 x 4’s attached to short 4 x 4’s or crossed 2 x 4’s, supported by a 1 x 10 running vertically down the middle and attached with L-braces.

You’ll want some simple shelves, but if your walls are glass they’ll need to be free standing. Sometimes, purchasing a couple of small, plastic sheds is preferable to building your own. After all, there’s a limit to what even do-it-yourself’ers want to make.

Materials for Building a Greenhouse

Choosing what materials to use in constructing your greenhouse will have multiple effects on its usefulness. The same holds true for those considering purchasing a pre-made greenhouse.

The first consideration is, of course, the roof material. The largest percentage of highest intensity sunshine comes during the late morning through early afternoon hours when the light strikes the roof. There are several choices for material and design that can affect how much of that sunlight energy enters your greenhouse.

Glass is traditionally one of the more popular choices. It transmits light well, it’s relatively easy to clean and it has excellent reflective properties that hold in the heat produced.

But glass is transparent, heavy, can be expensive and subject to breaking. Extreme temperature differences inside and out can cause spontaneous cracking. Accidentally bumping the glass can cause it to shatter.

As a consequence, and as the result of advances in materials over the last 20 years or so, many more greenhouses use plastic and composites for the roof. Plastics can be purchased that are completely transparent or only partly so, i.e. translucent. That helps control the amount of sunshine – helpful in climates that have long, summer hours of direct light and less cold winters.

Glass is still an option for those who want to invest in some system for shading the roof and several choices are available. There are inexpensive mechanical systems that use white cloth, bamboo, plastic shutters and others. For those with some money to spend, there are even systems that will sense the amount of sunlight entering and electrically open and close the shades!

Walls are the next major consideration. Here again, many are the traditional glass. When selected, they offer the same advantages and challenges as the roof, with the added proviso that they have to bear the weight of the roof. Most are embedded or alternated with some kind of load bearing rods, beams or other support materials.

A glass greenhouse can be a beauty to behold, but modern plastics and composites can also provide a lightweight, strong and attractive alternative. Some are even partially wood, aluminum and other materials, though these are more often used only on the lower half. There’s little point in building a greenhouse that doesn’t admit light – that’s just a shed!

Picking a material for the floor requires some thought, too. Wooden floors are inexpensive to build and replace as needed. But they don’t have the temperature control features offered by cement which traps heat and re-radiates it later in the day as the temperature cools. Choose something that offers good drainage and will last through several winters.

When choosing materials consider sunlight and heat control, the needs of the type of plants you intend to house and your own comfort. You’ll want something you can enjoy spending hours a day inside.

Greenhouse Accessories

Greenhouses are not just static structures that stand empty. They have moving parts and are filled with benches, tools and many other accessories that help support and care for the plants housed there. Tools, measuring instruments, and the like naturally come to mind for any avid gardener. But there are dozens of accessories for the greenhouse itself, as well.

Louvre’s, glass or plastic shutters that admit air, are often part of greenhouse design. They help ventilate the interior, a problem in areas where summer sunlight hours are long and hot. Like anything else, they can break and need to be replaced.

But even when they don’t break, the greenhouse shopper may want to consider replacing them with auto-louvres. These clever devices allow opening and closing the shutters automatically. Some work on a timer, others are triggered by temperature.

Galvanized steel braces are available that will allow you to shore up the base of your greenhouse. They act somewhat like a metal strap around a wooden barrel, giving it additional strength and supporting the structure. This can help prevent collapse during storms and even increase the support for the roof under heavy snow load.

Shelves have gone from static and boring to functioning works of art. There are aluminum shelves that can interchange heights. Others can be re-arranged into different geometrical shapes for attractive displays and maximizing space usage. They come in a variety of colors, with plastic liners, wheels and all sorts of different options.

Rainwater kits are a great addition to any greenhouse. They make watering the plants a breeze and optimize your water use. You can get small, single nozzles or entire tracks. Some have misting attachments, movable heads and other gizmos. Many are controllable by digital 24-hour/365-day timers.

Of course, when it comes to tools and instruments, the number and variety of available choices is just astounding. Soil thermometers, salinity gauges, moisture-level testers, phosphor and nitrogen level monitors… you name it.

There are heating devices in dozens of different styles. Some lamps or ‘toaster-coil’ types will spot heat a corner. Others, such as track systems, can be attached to the roof and heat the entire greenhouse in the winter.

A chemical factory of cleaning aids can be had today. Mildewcides, calcium carbonate removers, window cleaner, cement floor cleansers… an endless choice.

Ordinary garden tools are now made of many more materials than ever before. Don’t like metal trowels? Get a composite that’s stronger than steel and lighter than plastic. Want a shovel that telescopes out five feet or collapses to 12 inches, with a three-inch wide mouth? No problem.

So far, there doesn’t seem to be a tool that will robotically remove aphids or plant tulips, but it can’t be too far in the future.

Every kind of book imaginable to help you build your greenhouse, maintain it and care for the plants inside can be had online. If there’s a subject you need to know about, finding the information – and the tools to help you act on it – is just a few clicks away.

Planning Your Greenhouse

Before you buy or build a greenhouse, there are a number of considerations worth thinking about. You’ll save time and hassle by planning ahead. Remember, all the factors discussed below will need to be evaluated in light of what kind of plants you intend to have.

Greenhouses come in a hundred different styles. Pre-made greenhouses can be purchased in a range of designs, sizes and prices, offering several different materials (glass, plastic, polycarbonates, partial wood or aluminum). Building your own involves additional issues to address.

But whether you buy or build, you will be faced with many of the same problems to solve.

You’ll have to consider what kind of foundation to build or install – none, gravel, wood, cement or brick. You should consider whether you plan to cover the floor with linoleum or carpet or tile. Some floor heating systems can work within these, for example. They also affect how much time and effort in cleaning it you may need to invest.

You should consider the location carefully. Depending on where you live, what kind of trees are around your home and other factors, you may get a few hours of sunshine per day or more than a dozen. Climates differ also in the amount and severity of wind, rain, hail, snow and other variables.

Geography will obviously play a large role. More northern latitudes will get longer hours of summer sunshine, but very much less in the winter. The amount of sunshine per day is a key factor in planning any greenhouse. Though it can be compensated for somewhat by artificial lighting and heating systems.

Beyond hours of light, the amount of heat and moisture is heavily affected by climate. Even in northern latitudes there are significant differences. Summers in Northern Idaho are dry, implying a greater need for watering systems. Summers in the Northeast such as New Hampshire, by contrast, are much more humid and you may need to water less.

You need to evaluate all those relative to the proposed size and location of your planned greenhouse, constrained by the options available on your property.

You may have trees close to the house in one area, but further away on the other side. You may have a flat area suitable for a greenhouse, or a hill which could be flattened in a day with a bulldozer. Consider, too, the amount of wind, hail and rain you’ll get in one location versus another.

Though average wind and rainfall is, of course, the same over your entire property, the exact amount at your greenhouse’s location can vary. Trees can block wind and rain, high walls may shield one side.

The amount of rain on the greenhouse affects how you need to deal with drainage around it, and wind effects can be severe when you open the door or from storms. Think about orientation of the doors and windows, along with the location on your property. Think about how much water or mud may have a tendency to pile up around the outside walls and the doors.

It isn’t necessary to be an architect to build or install a greenhouse. But when you look at plans online, try to think like one. For those more interested in gardening than construction, that’s a challenge. But you’ll have more time for plant care in the long run if you spend some time thinking about building up front.

Building Your Greenhouse Foundation

Building a foundation for your greenhouse offers you many choices.

Some people, especially if they buy a pre-made greenhouse, will simply lay it on top of whatever ground exists at the location they choose. That may be gravel, or dirt or even grass. Some pre-made greenhouses come complete not only with roof and walls, but a floor, as well.

If you choose to build your own greenhouse, you’ll probably want to prepare the ground underneath it in some way. This could be as simple as smoothing the earth and laying down railroad ties spaced an inch apart. An alternative step up could be creating a simple platform of eight-foot 2 x 4’s or 1 x 6’s nailed to 4 x 4’s spaced out about every 18 inches under the slats. That way you have a solid base and drainage.

But those simple designs leave you with the problem of controlling weeds, replacing floor boards, controlling mildew and other issues associated with wooden floors.

The next step up is laying a cement foundation, similar to the type under many houses. This is easier than it sounds, but it requires more effort than the other alternatives and has a few potential drawbacks.

Creating a cement foundation requires laying out an area, smoothing it and building a temporary ‘container’ around the area you intend to pour. You’ll want to make it fairly smooth and level – not an easy thing to do unless you have a fair amount of experience pouring cement.

In the end, you’ll be left with a semi-permanent foundation which would be difficult to move or remove later if you change your mind about the location.

But a cement foundation will last longer and give you some options about heating. You could lay carpet or tile on top with heating tubes or wires underneath, for example. It’s easier to take care of and very sturdy. Cement floors also can absorb and reflect a lot of heat, which can be handy in a greenhouse.

Building a good cement foundation will require a couple of weekends. The materials, tools and construction plans are available at a hardware store or can be ordered online and delivered.

Beyond following the directions for mixing cement, creating the frame and properly forming the surface, the key is temperature and humidity. It’s important that you carry out the project when you expect moderate to warm temperatures, relatively low humidity and no rain.

Whichever option you choose, make sure you plan ahead. Make sure the floor is sturdy enough to support the benches, tables, pots and people that will be inside. After you have all that installed, it’s much tougher to replace flooring.

Building a Greenhouse Green

Greenhouses, or as they were known in the 19th century Conservatories, are freestanding structures that house plants and admit light to ‘feed’ them.

Plants don’t move around like animals, so they have to get their food in other ways. To some extent they pull it in from the soil by capillary action. ‘Capillary action’ happens, for example, when you soak water up with a paper towel held upright. The water flows up against gravity. Roots take in water and nutrients from the soil, while leaves soak up water and sunlight.

Why is sunlight helpful? Because plants use it as an energy source to drive photosynthesis, the process by means of which they use light to power processing and creating nutrients to sustain themselves, grow and reproduce. So, how does a greenhouse help plants any more than just planting them outside in the earth? How do they work?

Greenhouses typically have a roof and walls of glass or translucent plastic. Sunlight consists of a spectrum of light waves, some of which are invisible such as ultraviolet and infrared. Glass, and some kinds of plastic, allow all those waves in but only selected ones get out as efficiently.

Infrared, the wavelength that we sense as heat, doesn’t escape back through the glass as readily as the visible wavelengths. That heats the air inside the greenhouse, which is allowed to vent to the outside only partly, as most of them are fairly well sealed.

The combined effect of bringing in all that light energy, while only part of it escapes, causes the temperature to tend to be higher inside than out. Anyone sitting in a closed car in the summer sun is familiar with the effect. That’s why greenhouses sometimes used to be called hothouses.

Greenhouses, like a lot of artificial structures, help us control conditions in ways we can’t if plants are put in an outdoor garden. The effects of wind, temperature, amount of sunlight and other variables are often harder to control outside a greenhouse.

Along with the ability to regulate the amount of sunlight – by use of glass, shutters or screens – greenhouses make it easier to protect fragile plants from high winds. They also provide an environment that can be more comfortable in which to plant, pot and manage soil.

Along with their utility, greenhouses can be a beautiful addition to the home. Well constructed, or pre-made, greenhouses are often architectural marvels. The glass cage can be lovely, and the view to the variety of plants and vegetables inside turn a workhouse into a work of art.