Packages with seeds often contain information about sowing period in March in a cold frame. This date usually tends to be much earlier than the one relating to sowing in the ground. The cold frame allows for early planting, meaning also earlier and better harvests.
The first seeds are usually intended for spring vegetable cultivation, i.e. plants developing early under cover. When they reach their maturity, they can be transferred to a permanent place in the polytunnel. But this is not the only function of cold frames. Often, these small units are placed under a full-size greenhouse, to create even better conditions for thermophilic plants’ growth. They also contribute to protect crops against frost and temperature drops.
What is a cold frame really?
Usually a very simple structure, which looks like a square garden tunnel, just much smaller. It is often without a bottom end, and the walls are supposed to surround what will be grown inside. It can be a chest with a tilted window or it can look like a mini foil tunnel.
This time, in the Krosagro guide, we will talk about these garden constructions that support crops under cover.
How to build a cold frame?
The simplest cold frames can be built from boards, even recycled ones. Just impregnate the raw wood with a biodegradable agent, prepare the structure in a square or half circle shape , and then apply a covering foil on it. It is worth trying to make the construction as tight as possible. Every once in a while, ventilation is required to provide fresh air to the plants and even out the temperature inside.
Materials for cold frames and their cover may be different. You can use bricks, hollow blocks, and the cover must maintain the heat inside as long as possible. Dimensions must be well suited to your needs, plans and gardening ambitions.
Filling the cold frame
The inside is filled with good quality soil, after which seeds can be sowed. Inside, you can also put pots with seedlings. This is a good solution for plants that can hardly tolerate replanting. You can also additionally protect the emerging shoots from frost and low temperatures, covering them with straw or agro textile.