08.08.2018 |

Episode #8 of the course Advanced gardening by Alice Morgan


Hello there! Today, we’ll be talking about greenhouses. Greenhouse management depends on what kind of greenhouse you choose, so we won’t talk much about setting up a greenhouse. Instead, I’ll go over differences in a several popular greenhouse models so you’ll have the knowledge to choose which type is the best for you.


Introduction to Greenhouses

Greenhouses are clear buildings that provide a warm, regulated environment that will enable you to grow plants all year long, or at least extend your growing season. They can be made from glass, plastic, and polycarbonate and can be as small as a cold frame or as large as a warehouse. They stay warm because they take in the heat from solar radiation, which warms the air in the greenhouse. The greenhouse structure then keeps the warmed air from escaping. Greenhouses aren’t a new concept either. The principles behind them have been used since Roman times and have only grown more sophisticated as time has passed.


Types of Greenhouses

Free-standing greenhouse. A free-standing greenhouse is probably the mental image you get when picturing a greenhouse. They tend to be the most expensive of all the greenhouse options because they are an independent structure that requires permanent building materials. They have the advantage of being warmer than other structures because sunlight can enter through all four walls, and you can build them to give you as much space as you want. These greenhouse are great for people who want to grow large amounts of plants and can have heaters and other mechanized equipment added. They are also nice because they can provide an escape for people looking for quiet and solitude.

Lean-to greenhouse. Lean-to greenhouses are three-sided structures that are typically attached to a non-greenhouse wall, usually the wall of a house. These greenhouses are less expensive than free-standing greenhouses but will be limited to the dimensions of the permanent wall. These types of greenhouses tend to be fantastic for starting seeds and growing herbs, but not for growing large amounts of vegetables.

High tunnel. High tunnels are a type of free-standing greenhouse, but they aren’t heated and are more temporary. The goal of a high tunnel is to extend a gardener’s growing season rather than grow year long. When thinking of this style of greenhouse, imagine a wood or metal structure with thick plastic wrap stretched over it. Here, the gardener can plant their crops when it’s still too cold outside for normal planting, remove the plastic when it’s warm enough to support the plant, and then replace the covering when it begins to get cold again. They are much cheaper than a regular free-standing greenhouse.

Low tunnel. Low tunnels are just like high tunnels. Whereas high tunnels can be as tall as a one-story house, low tunnels are only 3-4 feet (90-120 cm) high. Their advantage is that they can be placed over existing rows and structures (like raised beds). They are also cheaper than high tunnels because they require much less material.

Cold frames. Cold frames are mini free-standing greenhouses. You can place them over seedlings to get them going a few weeks prior to when you’d be able to plant them normally. They can also be used to overwinter dormant plants that would not normally be able to survive the winter temperatures in your area.


Greenhouse Management

Regardless of what kind of greenhouse you choose, some maintenance chores are universal. You’ll still need to water your plants frequently. It is also important to maintain humidity, so another good practice is to spray the ground of your greenhouse, particularly in the summer. Be careful to avoid foliage, as the water drops can act as sun magnifiers and scorch leaves. They will also need to be ventilated in warm months and may even require shading. During the winter, you’ll need to make sure that the glass is clean to allow for maximum sunlight.

You’ll also need to continue your usual garden care activities, albeit under cover. Plants will need to be fertilized, scrutinized for pests, and repotted.

That’s it for today’s lesson. Greenhouses can be a lot of work to set up but can add a whole new dimension to your garden and bring a lot of joy. Tomorrow, we’ll cover seeds and seed saving, so you can save the plants you love for years to come.


Recommended books

Greenhouse Gardener’s Companion, Growing Food & Flowers in Your Greenhouse or Sunspace by Shane Smith and Majorie Leggitt

How to Build Your Own Greenhouse: Designs and Plans to Meet Your Growing Needs by Roger Marshall


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