How to Build a Greenhouse

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A greenhouse is a structure of glass, metal, or plastic that encloses one or more plant beds.

The plant beds are typically provided with the appropriate mix of sunlight and ventilation to cultivate plants out-of-doors at higher latitudes or during colder weather.

It may also include artificial lighting and temperature control.

To build a greenhouse you will need to buy the following materials:

Protective plastic – You can use some plastic tarps or any other kind of tarp that you don’t mind tearing apart.

A border – You can go with wire, metal sheeting, or wood. Wire is the easiest choice and also the cheapest.

An H frame – A heavy duty commercial or home-made frame that will hold up your plastic sheeting against your border. The frame should be wide enough so that it will be able to cover at least three sides of the greenhouse.

If you are using wire for one or more of your borders, you can probably get away with a lighter duty frame than if you are using either metal sheets or wood as your border.

Gravel – This will go on the floor of your greenhouse to act as an insulator between it and the soil outside. You can use any sort of gravel for this – it doesn’t have to be top quality stone, but don’t use anything that has sharp edges or glass in it. A good alternative here would be to use wood chips.

Plant Containers – You’ll need enough of these to fill up your greenhouse space with plants. They can be large or small, according to what you plan on growing in them. If you are buying pots, get ones that are at least 6″ deep. They will give the roots more room and keep them warmer.

Soil – You will need enough of this to fill up your greenhouse plot and plant containers, unless they are not going in the ground. Make sure that your soil is a good quality potting mix or it won’t make a very good hotbed. This year I mixed my own soils for each bed, but next year I will probably go ahead and buy the 30 cubic foot bag of bagged potting soil. The price is right!

Plants – You will want to find seeds or starter plants that are recommended for growing in hotbeds, coldframes, or greenhouses. Tomatoes, peppers, cucumbers, beans, peas, corn – anything that you can grow in your traditional garden is a good candidate for your greenhouse.

If you are growing from seed, make sure that you get seeds with at least a 5 rating on the Heat-Needed Scale. Seeds with a rating of 0 to 4 indicate that they will germinate in cold soil, but will need some warmth before they will sprout. Early spring plantings will need a higher heat rating to germinate and grow well.

Water – Keep plenty of water on hand for your plants, especially as they start to become rootbound in their pots or the weather gets very hot during mid-summer. You can use seeds that are sold as “heat-loving” if you want to have an easier time getting them to germinate.

Lastly, you will need some kind of insulation for the roof or top of your greenhouse structure if it is open on top. This can be bubble wrap, foam board insulation panels, straw bales, or any other light weight material that will keep the heat in during the day and keep the cold out at night.

No matter how much insulation you use, do not go overboard on it or you will risk overheating your greenhouse and killing off your plants.

You will also need some type of ventilation if you are using a solid roof for your greenhouse. A ventilation flap at one end of the structure with a window or door that can be left open during the day and latched shut at night will work well. A small fan can also help to keep air moving and prevent overheating .

The next thing you should do is to take your protective plastic tarp out into your greenhouse area with a friend, one of you holding up one side of the tarp while the other sticks the frame up underneath it. Measure off how much tarp you are going to need, depending on how large your greenhouse is, and cut the tarp accordingly.

You should now have one side of your greenhouse framed in with either wire or wood. PVC pipe works well for this too if you don’t mind the expense. I like to frame in my greenhouse at least once before I attach the plastic sheeting, just for good measure.

Now you can estimate where you will need to put your support posts into the ground, approximately 2 feet or more deep depending on what type of soil that you have. You will want one post every 3 – 4 feet along the base of your greenhouse.

Now you can attach the plastic to the wire or wood framework using two nails or screws on each side, where the wire is connected together. This will hold your plastic in place until you get all of the posts set into the ground and ready for support beams to be nailed into them on either end of your greenhouse.

When that is done, you can attach the wire or wood beams to the posts on one end of your greenhouse. If you have a solid roof, you will only want to use 1 support beam at each end. Just nail it securely to each post and leave about 3 feet hanging over the other side so that it doesn’t slide off when you have it installed.

If you have a slanted roof, use 2 support beams at either end of the greenhouse. Measure up 3 feet from the bottom and cut another beam to fit so that it will attach securely to both posts at one corner, matching up evenly with the roof above. Make sure to keep your overlap well covered by plastic sheeting to ensure that no rain gets in.

Now you can start covering your greenhouse with plastic, working from one end to the other and making sure that it is attached securely at each corner and along the support beams. You should staple up any loose areas of plastic and trim off excess before moving on to the next section and overlapping by a few feet.

Now that your greenhouse is covered completely with plastic sheeting, you can attach some kind of ventilation to one end if desired. PVC pipe or wood rods will work well for this. Leave the top open so that heat can escape during the day, and then at dusk you can close it up so that no cold air gets in overnight.

You will want to get a thermometer so that you can decide how open or closed your ventilation window should be during the day. You want this end of your greenhouse to remain around 20 degrees Celsius or 68 Fahrenheit at night while the other end may require closing up completely and letting the heat from within build up until it starts getting too hot. This also means that you should have some type of heating source in your greenhouse because it will be cooler at night than anywhere else inside your house.

A small heater or even a heater lamp can work well, just make sure that you use something that is safe and won’t overheat the space inside and cause a fire hazard.

Of course, you are going to have to do some watering for your plants, but I wouldn’t recommend using a hose because it could possibly cause the green house to collapse under the weight. You can simply fill up a large container of water and carry it inside so that you will be able to water all of your plants by hand every day.

This way, you can also add some fertilizer or plant food to the water and it will be good for them while they are growing. Plants don’t like salt, so this is definitely not something that you should do indoors. Also, make sure that you wash off your hands before touching your plants because the oils from your skin will cause them to stop growing.

Make sure that you install some type of flooring for your greenhouse so that moisture will not cause problems with the foundation, and if you are installing it indoors, you should put down a layer of plastic sheeting to keep the humidity out so that it doesn’t damage any surrounding furniture or walls.

Also, because this is inside, there still needs to be some ventilation. You can do this by hanging up a sheet or old shower curtain in front of the open end, just make sure that sheet is secured so that it doesn’t fall down when you are watering your plants.

To help keep warm at night, you may want to consider installing an automatic vent opener on the side of your greenhouse facing the house. This is just an electric device that will automatically open and let out excess heat when it starts to build up at night, then close again in the morning so that your plants don’t get too hot during the day.

As far as what kind of plants you can grow inside a greenhouse, most herbs do really well without any extra lighting, but you can also grow things like tomatoes and peppers if you do decide to install some type of supplemental lighting.

So this is how to Build a Greenhouse.


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