When the winter turns to spring on the calendar, many of us with a green thumb start getting the itch to plant vegetables. Starting seeds indoors can tide us over for a while, but what we are really anticipating is that bountiful crop springing up outside in the garden. If the warmer weather is sluggish in arriving – and frosts are still a threat — what can be done to speed up that first spring crop? The answer is hot bed gardening!
Similar to cold frames, hot beds are structures that look like miniature greenhouses (four walls and a top) used to protect young plants and encourage them to grow when conditions outside are less than ideal. Typically, they are box-like structures with a clear glass or plastic top that allows light to penetrate.
The difference between cold frames and hot beds however is that – as you would expect from the name – a hot bed is heated in some way. Traditionally hot beds are heated with horse manure, although some modern hot beds also use electric cables or heating coils.
The history of hot beds
The use of hot beds to grow out-of-season produce is nothing new. Parisian gardeners made a decent living in the 1900s supplying cities such as London, England with a bounty of lettuce, turnips, carrots and asparagus between the months of January and March.
Closer to home, in cities such as New York and Boston, farmers operated thousands of hot beds, which provided both food and jobs to many Americans. With the abundance of fresh horse manure in those days, the cost to provide food to those cities was far less than it is today to grow food in greenhouses or to transport it from warmer states — even when you account for inflation.
Making your own hot bed
If you think you’d like to try building your own hot bed for an earlier spring crop, you may use these instructions as a guide.
The construction of the frame is fairly simple. It consists of four walls, with the back wall being higher than the front, so that the top will have a slope to it. The frame is usually made of wood, but it may be made of other materials.
The traditional dimensions are 12 feet long by four-feet wide, but this can be adjusted to a size that suits your own garden. The typical height is nine inches in the front and 18 inches in the back, with a bracing strut that is fitted front to back at the top of the frame.
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The roof or lid
On top of the hot bed frame is a lid made of a clear material such as glass or plastic. Polycarbonate roofing sections may also be used. The lid is not fixed to the frame but rather it is constructed in such a way so that it can be opened either by raising it or by sliding it up and down.
The best type of manure to use for a hot bed is horse manure, because it is hotter than other types of manure. And when it comes to hot beds, the fresher the manure, the better.
But you shouldn’t simply dump this into your hot bed – there is some preparation involved.
Make a mixture of straw and manure and create a loose pile in the shape of a pyramid. By using a pitch fork and shaking it loose as you go, you will get the best results. Leave the pile for three days to allow it to get hot enough to generate steam.
On the third day, get out your pitch fork again and move your pile to another adjacent location, shaking the manure loose as you go. The idea is to turn the original pile upside down so that the top becomes the bottom, and the bottom becomes the top.
Leave this pyramid to sit for another three days and then repeat the process one more time.
If you have dry weather during this time, you will have to add water following each time you turn the manure. A gallon of water for every foot of height is the norm.
After nine days, the manure should be fermented enough to use in your hot bed. There are two main methods of filling a hot bed.
- The pile method – Create layers of manure about five inches in depth and two inches wider than the frame and then tap it down with a fork. Repeat this process until you have a good two to three feet of manure and then place the hot bed frame over top.
- The brick build method – Fill the bed with about five inches of manure and tap down as you go.
Once the hot bed is constructed and filled with manure, it will take about 12 hours for it to start to heat up and about three days to reach its maximum heat. You can use a thermometer to help you determine when it has reached the maximum temperature. Once it reaches maximum heat, it will plateau before it starts to cool down again.
When the temperature has reached its plateau, it is time to add a six-inch layer of soil before finally planting your seeds or seedlings.
A few more tips for success
Gardening with hot beds can be a bit tricky when you are first getting started, but the early and bountiful crops are well worth the effort. Here are a few more tips to help maximize your chances of success:
- Location, location, location – Your bed will do best when located in a high and well-drained spot.
- Insulation – You’ll need to protect your hot bed from the cold soil around it. Depressing it in a large pile of manure works. If that is not an option for you, you can use Styrofoam or other rigid-board insulation.
- Control the temperature – At night, it is a good idea to cover the top with some kind of insulation. Even old rugs will help. When days get sunny, but sure to raise the top of the frame to keep the inside temperature from getting much above 90 degrees Fahrenheit.
Enjoy a wonderful – and early – spring harvest through the use of hot bed gardening.
What tips and advice would you add? Share your thoughts in the section below: