Greenhouse Gardening: Creating a Controlled Environment for Year-Round Plant Growth

A quick quiz: Do you find yourself thinking about spending time in your garden months before the spring planting season begins? Have you been craving a freshly grown veggie that isn’t particularly suited for the climate in your region? Do you find fall harvests bittersweet — despite the produce they’ve yielded — because they mean you’ll have to wait half a year to garden again?

Not to sound like an infomercial, but if your response to any of these questions is yes then greenhouse gardening might be a good fit for you.

Greenhouses, which can range from large, freestanding structures to simple lean-tos, let you control your plants’ environment.

When you have the ability to adjust things like temperature, humidity, and sunlight exposure, you can grow vegetables, herbs, and flowers year-round. You can even cultivate exotic plants that normally wouldn’t survive in your local conditions. 

Pick a structure

If you’re considering greenhouse gardening, a good starting point would be to research the types of structures available to you. The idea is to find the best option for your budget, space, and gardening needs.

Here are some good possibilities for year-round gardening.

Insulated panel greenhouses

These greenhouses are constructed with polycarbonate or foam-insulated panels that can significantly reduce heat loss during cool months and reflect excess heat in the summer.

Strengths: Not only does their thermal insulation help maintain a stable internal environment, but they’re also energy efficient.

Weaknesses: The specialized materials that make greenhouses effective also make them a more expensive option.

Geodesic dome greenhouses

Also known as greenhouse domes, these structures are made of a dome-shaped frame covered with plastic or polyethylene film or polycarbonate panels.

Strengths: The greenhouses’ aerodynamic design allows wind to pass over them without catching on any flat sides. They can also shed snow. And because of the greenhouses’ spherical shape, the plants inside benefit from efficient exposure to sunlight throughout the day.

Weaknesses: They’re a bit more complex to construct and can be expensive. Also finding replacement coverings can be challenging.

Freestanding greenhouses with climate control systems

These are standalone structures equipped with advanced climate control systems, including heating, cooling, and ventilation systems, to regulate the internal environment.

Strengths: They’re designed to provide precise control over internal conditions, making them ideal for year-round growing. They also provide a lot of flexibility in terms of where you place them.

Weaknesses: Because of their ongoing energy usage, they have higher operational and maintenance costs.

Underground or pit greenhouses

Also known as a walipini, this type of greenhouse is built into the ground and uses the earth's natural insulation to moderate temperature fluctuations.

Strengths: Underground greenhouses are less affected by external weather conditions. They tend to maintain a constant temperature, and they are more energy-efficient than some of the other options.

Weaknesses: These greenhouses are more complex and potentially expensive to construct. And providing the plants inside with adequate light and ventilation can be challenging.

Glass greenhouses with double or triple glazing

By applying glazing, traditional glass greenhouses can be adapted for year-round use.

Strengths: These greenhouses provide excellent light transmission. The improved insulation with multiple glazing layers helps maintain stable temperatures.

Weaknesses: Glass is more expensive and fragile than other materials, and you can expect a higher initial cost for double or triple glazing (though that cost can be offset by the savings in heating costs over time).

Polycarbonate greenhouses

The polycarbonate panels on these greenhouses provide effective insulation. They can also be equipped with thermal screens to enhance temperature control even more.

Strengths: Polycarbonate greenhouses are durable and less susceptible to breakage than glass. They provide good insulation and light diffusion.

Weaknesses: Over time, polycarbonate panels can become discolored or less clear, impacting light transmission.

Finding your greenhouse a home

Just like any gardening spot, your greenhouse’s location is an important decision.

In most cases, you’ll want a spot that gets at least six to eight hours of direct sunlight a day. But you might also need to protect your greenhouse from strong winds that, depending on the type of greenhouse you have, could damage your structure. Consider windbreaks like hedges, fences, or existing buildings, positioned at least 15 feet away to avoid affecting airflow.

Ideally, your greenhouse will be in a spot that’s convenient for you with easy access to a water source and — if you plan to use electric lighting, ventilation systems, or heating equipment — a power source.

In addition to these considerations, look for:

• A flat, level area that will allow for a stable foundation
• Well-drained soil where flooding is less likely
• A spot free from obstructions like large trees or buildings that could cast shade on your greenhouse

Keeping your plants comfy: temperature control

Depending on your location and the season, the shelter your greenhouse provides won’t be enough to provide the optimum temperatures and humidity levels for the plants it houses.

When you need heaters, your options include space heaters, radiant heaters, and fan-forced heaters. 

As for cooling systems, evaporative coolers or misting systems can be helpful by introducing moisture and lowering air temperature. Shade cloth can also be used to block out some sunlight and prevent overheating.

Plan to monitor the temperature and humidity levels in your greenhouse regularly. You can use thermometers and hygrometers to track these factors and adjust your ventilation or heating/cooling systems as needed.

Ventilation considerations: breath of fresh air

Speaking of ventilation, even though the goal of a controlled environment is to protect your plants from conditions that put them at risk, your plants will still need fresh air.

Not only that, but proper ventilation in your greenhouse will reduce the risk of mold, mildew, and fungal diseases. It will support your temperature control efforts and provide your plants with fresh carbon dioxide, which they need to create energy.

You can encourage ventilation with strategically placed windows, vents, and doors, which will create natural air circulation patterns. 

Or you can use exhaust fans to actively pull out hot air and promote air circulation. This approach is especially valuable in larger greenhouses.