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How to Build a Cold Frame Greenhouse in Your Backyard

Cold Frame Greenhouse

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A cold frame greenhouse is basically made from wood or metal frames with transparent lids, giving the user a versatile cheaper option to a full greenhouse. They can be constructed in various sizes, shapes, and designs.

They allow gardeners to grow plants that would otherwise be too delicate or vulnerable to survive in cold climates, especially during the early spring and late fall seasons. The design of the cold frame also makes it easy to regulate the temperature and humidity levels, which can be adjusted according to the needs of the plants being grown.

You can build a cold frame greenhouse from wood, plastic, concrete blocks. All you need are sides and a removable or hinged top placed on top of the soil.

How to Build a Cold Frame Greenhouse

Building a cold frame greenhouse is a great way to extend your growing season and protect your plants from harsh weather conditions.

Here are the steps to build your own cold frame greenhouse:

Choose Your Location… Select a flat, level spot that receives at least six hours of direct sunlight per day. The area should also be well-draining and accessible for watering.


Build the Frame… Construct a wooden, brick or metal frame that is the desired size of your cold frame greenhouse. The frame should be sturdy enough to support the weight of the transparent lid and withstand outdoor elements.

Add the Transparent Lid… Attach a transparent lid to the frame using hinges or screws. The lid can be made of glass, polycarbonate panels, or clear plastic.

Add a Ventilation System… Install a ventilation system to regulate the temperature and humidity levels inside the cold frame greenhouse. This can be as simple as adding a small opening or vent at the top or sides of the frame.

Prepare Your Soil… Before planting, prepare the soil by removing any debris, rocks, or weeds. Add organic matter, such as compost or aged manure, to improve soil fertility.

Plant your Seeds or Seedlings… Once the soil is prepared, plant your seeds or seedlings according to the planting instructions for your desired plants.

Monitor and Maintain… Monitor the temperature and moisture levels regularly and adjust as needed. Keep the cold frame greenhouse clean and well-maintained to ensure optimal plant growth.

Building your own cold frame greenhouse is a relatively simple and inexpensive project that can provide you with fresh produce throughout the year. With proper care and maintenance, your plants will thrive in this protected environment, allowing you to enjoy the fruits of your labor even during the colder months.

Here’s a video on building a cold frame:

Is a Cold Frame as Good as a Greenhouse?

A cold frame and a greenhouse are two different types of gardening structures that offer different benefits and limitations. While a greenhouse provides a fully enclosed and controlled environment with heating and cooling systems, a cold frame is an unheated structure with a transparent lid that helps protect plants from harsh weather conditions and extend the growing season.

In terms of plant protection and season extension, a cold frame can be just as effective as a greenhouse, especially for hardy plants and cool-season crops. A cold frame can help protect plants from frost, wind, and heavy rain, and can be a great way to start seedlings or grow plants that prefer cooler temperatures.

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However, a cold frame is typically smaller than a greenhouse and may not offer as much space or versatility in terms of plant growth.

While a greenhouse provides a more controlled and stable environment with temperature and humidity control, which can be especially beneficial for growing tropical plants, starting seedlings early, and extending the growing season even further.

A greenhouse also offers more space and flexibility in terms of plant growth and allows for a wider variety of plants to be grown. A cold frame and a greenhouse both have their advantages and disadvantages, and the best choice for you will depend on your specific gardening needs and goals.

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How Hot Does a Cold Frame Greenhouse Get?

The temperature inside a cold frame greenhouse can vary widely depending on several factors such as the outside temperature, the amount of sunlight, and the ventilation. On n average, a cold frame greenhouse can reach temperatures that are 5 to 20 degrees Fahrenheit (3 to 11 degrees Celsius) warmer than the outside temperature.

The temperature inside a cold frame greenhouse can also vary throughout the day, with the highest temperatures usually occurring in the late afternoon or early evening when the sun is at its strongest.

In general, a cold frame greenhouse is designed to maintain a temperature range of about 40 to 80 degrees Fahrenheit (4 to 27 degrees Celsius), depending on the season and the specific plants being grown.

To regulate the temperature inside a cold frame greenhouse, it’s important to monitor it regularly and make adjustments as needed. This can be done by opening or closing the lid, adding or removing insulation, or installing a ventilation system to help regulate the airflow.

It’s also important to keep in mind that plants have different temperature requirements, so it’s important to research the ideal temperature range for the specific plants you are growing and adjust the temperature of the cold frame accordingly. Check out Amazons line of cold frame greenhouse here.

What are the Disadvantages of Cold Frames?

While cold frames have several advantages for extending the growing season and protecting plants from harsh weather conditions, they also have some limitations and disadvantages that gardeners should be aware of:

Limited Space… Cold frames are typically smaller than traditional greenhouses and may not offer as much space for plant growth or as many options for plant varieties.

Lack of Temperature Control… Unlike a greenhouse, a cold frame does not have a heating or cooling system to regulate the temperature, which can limit the types of plants that can be grown and make it more challenging to maintain consistent temperatures throughout the year.

Limited Air Circulation… Cold frames can be prone to poor air circulation, which can lead to fungal diseases or pest problems. Proper ventilation is important to ensure a healthy growing environment.

Risk of Overheating… In warmer climates or during the summer months, a cold frame can become too hot and potentially damage or kill plants if not monitored closely.

Requires Regular Maintenance… Cold frames require regular maintenance, such as cleaning and sterilizing between plantings, to prevent disease and pest issues.

Where is the Best Place to Put a Cold Frame?

The location of a cold frame is an important consideration for successful plant growth.

Here are some tips on where to put a cold frame:

Choose a Sunny Location… A cold frame should be placed in a sunny location that receives at least six hours of direct sunlight per day, especially during the winter months when daylight hours are shorter.

Orient the Cold Frame Correctly… Position the cold frame so that the back wall faces north, and the front faces south. This will maximize the amount of sunlight that the plants receive and help prevent overheating.

Consider the Wind… Avoid placing the cold frame in a windy location, as this can cause damage to the structure and potentially harm the plants. Instead, choose a sheltered area, such as near a building or a fence.

Ensure Good Drainage… A cold frame should be placed on level ground with good drainage to prevent waterlogging and root rot.

Good Accessibility… Consider the ease of access to the cold frame, especially if you plan to use it for vegetable gardening. Make sure it is easily accessible for watering, planting, and harvesting.

Does a Cold Frame Need Clear Glass?

While clear glass is a popular choice for the lid of a cold frame greenhouse, it is not the only option. In fact, clear plastic or polycarbonate materials can be just as effective and have some advantages over glass.

Clear plastic or polycarbonate materials are lighter than glass and less likely to break, making them a safer option. They are also more affordable and easier to work with, making them a popular choice for DIY cold frame projects.

Additionally, clear plastic or polycarbonate can provide the same amount of light transmission as glass while also offering UV protection, which can help prevent damage to the plants.

Keep in mind that the lid of a cold frame greenhouse should be transparent to allow sunlight to penetrate and heat the interior of the structure. So, whether you choose clear glass, plastic, or polycarbonate, the lid should be transparent and allow light to pass through to maximize plant growth.

Why is a Cold Frame Angled?

A cold frame is angled to optimize its exposure to sunlight and to provide the best growing conditions for the plants inside. When a cold frame is angled, the lid or cover is positioned at an angle to the ground, which allows it to capture and retain more sunlight during the day.

The angle also helps to direct rainwater away from the lid, which prevents water from pooling and causing damage to the plants or structure.

The angel also provides better light exposure and drainage, an angled cold frame also allows for better air circulation, which is essential for healthy plant growth. The angle helps to create a natural convection current, which allows fresh air to flow in and stale air to flow out, preventing the buildup of excess moisture and reducing the risk of fungal diseases.

It can also provide some insulation benefits. The angle helps to trap warm air inside the structure, which can help keep the plants warm during cold winter nights.

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Can you Grow Seeds in a Cold Frame?

Yes, seeds can be grown in a cold frame as long as the temperature inside the frame is warm enough for germination. The temperature requirements for germination vary depending on the type of seeds being planted, but most seeds require soil temperatures between 60-80°F (15-27°C) for optimal germination.

In the early spring, when temperatures are still cool, seeds can be started indoors and then transplanted into the cold frame once they have developed into seedlings. Alternatively, some cold frames can be heated with an electric propagator or heat mats, which can help raise the soil temperature and promote seed germination.

When planting seeds in a cold frame, it’s important to keep the soil moist and well-drained, as excess moisture can lead to fungal diseases. Proper ventilation is also essential to prevent the buildup of excess humidity, which can also lead to disease problems.

What are the Different Types of Cold Frames?

There are several different types of cold frames, each with its own unique design and benefits.

Here are some of the most common types of cold frames:

Traditional Cold Frame… A simple, rectangular structure with a sloping lid that can be opened to regulate temperature and humidity.

Hinged Cold Frame… Similar to a traditional cold frame, but with a hinged lid that can be opened easily for ventilation and access to the plants inside.

Portable Cold Frame… A lightweight, movable cold frame that can be placed over a garden bed to protect plants from the elements.

Hoop-Style Cold Frame… A structure made from a series of curved hoops covered with plastic or other materials. These can be freestanding or attached to an existing garden bed.

Window-Mounted Cold Frame… A small, compact structure that can be mounted directly onto a windowsill, providing a convenient and space-saving way to grow plants indoors.

Raised Bed Cold Frame… A cold frame built on top of a raised garden bed, which provides additional protection and insulation for plants.


Building your own cold frame or several is not the difficult, and they work well in smaller spaces. If you’re renting or live in a condo or apartment it’s a great inexpensive way to have some fresh vegetables and herbs.

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