Cold frames are enclosures built to provide protection to plants during the cooler growing seasons. The roof of the enclosure is built to be transparent in order to allow sunlight in, while the enclosure itself prevents the escape of heat that would otherwise happen at night when the temperatures dip. Cold frames have several applications, but the primary benefit to using them is that they can help you to get jumpstart on your growing season or help you to extend your growing season.
Cold Frames Explained
Greenhouses have long been a popular addition to many properties. These heated outdoor spaces have helped many a gardener grow tomatoes and cucumbers right through the winter months and also provide the space needed to start seedlings in the coolest parts of early spring. Cold frames, as the name would imply, are not at all heated like greenhouses are. The warmth that the cold frames maintain inside of them comes strictly from heat generated by the sun and the plants themselves. The temperature inside of a cold frame may only be a few degrees higher than outside, but these few degrees can mean the difference between insulated soil and losing your plants to a late spring frost or an early autumn hard freeze.
There are dozens of kits available to help you build a cold frame, but it is actually pretty basic in design. Cold frames are essentially miniature greenhouses that may be portable, depending on your needs. Some prefer a combination of permanent cold frames and portable cold frames that can be used where needed and then stored away until temperatures start to slide downwards again.
The traditional design for cold frames involved the building of a two or three-foot tall frame that was then topped off with recycled glass windows. A sloped design is typically preferred because it allows for better runoff after rainstorms, and also helps to maximize the amount of winter sunlight that filters into the cold frame. A hinge is often installed in order to allow ready access to the plants inside of the cold frame, and also to help prop open the frame in order to allow fresh air to circulate on warmer days. Some have found that a small heating panel in the soil beneath the cold frame can help to provide the insulation plants need on the coldest winter days.
Benefits Of Cold Frames
If you live in a zone where winters can last late and arrive early, then cold frames can help you to extend your harvests so that you are getting as much food as possible from your garden. When spring is late in arriving, it can be hard to get a good crop started in a timely manner. This can then delay your harvests and even leave your plants vulnerable to attack from late summer insects or even the harsh summer heat itself.
Starting your plants in your greenhouse and then moving them to a cold frame can help them to better acclimate to the cooler temperatures they will experience after the warm environment in your greenhouse. Your seedlings will get plenty of direct sun, and still maintain the steady temperature that will protect them when temperatures outside dip down into freezing at night.
Cold frames can also help you to enjoy crops year-round, when things like fresh lettuce, fresh spinach, or even carrots are hard to come by. If you have the space to dedicate to it, you can grow different vegetables in several cold frames, essentially ensuring that you don’t ever have a non-growing season. Some of the other crops that should thrive inside of a cold frame include the following:
While the soil requirements of plants will vary, it is essential that you have well-draining soil inside of your cold frame. Many find it useful to dig about ten inches down when constructing their cold frame, and layering gravel, fresh horse manure, and a quality soil. The manure will not only provide a fertilizer source for your plants, but it will also help to naturally boost the temperatures in the cold frame as the manure breaks down over the course of time. Your cold frame should have at least six inches of soil for the plants to grow well in.
Maximizing Your Cold Frame Usage
There are a few tips that can help you to get the most benefit out of your cold frames, in order to ensure that you are never without fresh vegetables in one form or another.
- Southern exposure for your cold frames, along with the sloped roof, will help to maximize the amount of sunlight that your cold frames receive each day.
- Use a windbreak where possible to help maintain a steady temperature; a chilling wind can quickly drop the temperatures in your cold frame. Setting the cold frames up against your greenhouse or your house can provide a good windbreak.
- The spot where you place your cold frame should have good drainage; otherwise you run the risk of waterlogged plants. Good drainage will help to maintain the temperature of the cold frames.
- Use recycled lumber from around your property or that others are throwing out. This can help to keep your build costs down.
- In lieu of wood, you can use bricks or even cement to build up the sides of your frame; they may be somewhat more expensive than wood, but they can be a good permanent solution to your need for cold frames.
- Remember that the rear of the cold frame should be at least three inches higher than the front of the cold frame, with a gradual slope.
- Recycled glass windows are the best choice for your cold frames, but clear plastic sheeting can also be used. Keep in mind that plastic will lose heat a lot faster than glass will, so you will need to double-layer the plastic sheeting.
- If an unexpected winter storm is moving in, use a blanket or landscaping sheeting to cover the cold frame. A hot water bottle inside of the cold frame can also help to slightly raise the temperature of the cold frame and get your plants through a particularly cold night or severe ice storm.
Cold frames are wonderfully versatile tools that no serious gardener should be without. The benefit of having somewhere to harden your plants for growing outdoors is incredible; no longer will you be transplanting delicate seedlings directly into the cool ground from a nice warm greenhouse or growing shed. The shock of transplant and the temperature difference has seen many a gardener losing many of their seedlings. By allowing your seedlings to gradually adjust to the outside temperatures, you will be growing stronger plants that can focus on the task of producing fruit, rather than needing to survive transplant shock and try to regrow damaged greens.
If you have taken cuttings from other plants or trees, then over-wintering them in a cold frame can help them to root a lot more successfully than inside of your home where the temperatures might fluctuate too much in the winter.
Before you build your cold frames, do a bit of careful planning in order to determine how many you can use and whether you are better suited for putting in permanent or portable cold frames. You truly won’t regret building cold frames; they can mean the difference between fresh vegetables for dinner in the very early parts of spring and fearing your frozen and canned stores might not get you through to the warmer growing months.