Lesson 2.4 Hotbeds
Completion requirements
Section 2: Structures for Producing Plants
Lesson 4: Hotbeds
A
hotbed
is a bed of soil heated with fermenting manure or electricity. It generally is covered in glass and used for propagating plants and forcing early vegetables, fruits, and flowers.
A hotbed is really a heated cold frame. You can also think of it as a miniature greenhouse, providing the same benefits with limited space at minimal expense. It is a means for extending the growing season - to give an early start to warm-season vegetables and fruits, such as tomatoes, peppers, and melons.
For more information about hot bed gardening, click here.
A hotbed is really a heated cold frame. You can also think of it as a miniature greenhouse, providing the same benefits with limited space at minimal expense. It is a means for extending the growing season - to give an early start to warm-season vegetables and fruits, such as tomatoes, peppers, and melons.
For more information about hot bed gardening, click here.
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Similar to a cold frame, a hotbed is a rectangular box with the back higher than the front, covered with a transparent roof. It can be of any size, provided the plants inside it are within easy reach.
The sides of a hotbed can be almost any material such as wood, brick, masonry block, or concrete.
Hotbeds offer significant advantages over cold frames as follows:
The sides of a hotbed can be almost any material such as wood, brick, masonry block, or concrete.
Hotbeds offer significant advantages over cold frames as follows:
- They are much more effective in extending the growing season.
- They can accommodate a greater variety of plants.
- The manure used for heating can eventually be used as a plant nutrient in gardens.
Several days after preparing the bed, its temperature may reach about 35 degrees Celsius due to the heat produced by the decomposition of the manure. When the temperature drops to 30 degrees Celsius, seeds can be planted or plants can be moved
into the hotbed structure. A soil thermometer should be used. If temperatures start to rise, the roof of the bed can be opened to effect cooling. Periodic ventilation is similarly accomplished.
If electric heating is used, the heating cables are embedded in a layer of sand just below the soil. A hard mesh cloth is placed between the layers of sand and soil to prevent damage to the cables when the soil is being worked for planting. Thermostats are used to control the temperature of the bed.
Methods of heating the beds include electric cables, light bulbs, and hot water. Traditionally, manure has been used. Horse manure is considered best because of its high fibre content. The manure, about 30 centimetres deep or deeper, is packed into a pit beneath the frame and a 15 centimetre layer of good soil is placed on top.
Hot water heating systems, including steam, are normally useful only for large commercial hotbeds and are seldom used for the average home hotbed.
If electric heating is used, the heating cables are embedded in a layer of sand just below the soil. A hard mesh cloth is placed between the layers of sand and soil to prevent damage to the cables when the soil is being worked for planting. Thermostats are used to control the temperature of the bed.
Methods of heating the beds include electric cables, light bulbs, and hot water. Traditionally, manure has been used. Horse manure is considered best because of its high fibre content. The manure, about 30 centimetres deep or deeper, is packed into a pit beneath the frame and a 15 centimetre layer of good soil is placed on top.
Hot water heating systems, including steam, are normally useful only for large commercial hotbeds and are seldom used for the average home hotbed.
In addition to the concerns related to breaking the glass cover of the hotbed, safety concerns centre mainly on the use of electrical equipment. When laying the electrical cable, be careful not to damage the insulation covering of the cable
and avoid kinks that can damage or break the cable. When using light bulbs, always use waterproof wiring and sockets.
The safety of the plants can also be in question. Care must be taken to provide appropriate drainage for hotbeds. Excess water can stop the decomposition process of the manure layer, causing the temperature in the bed to drop quickly. Plants can be destroyed almost immediately by excessive cold.
The safety of the plants can also be in question. Care must be taken to provide appropriate drainage for hotbeds. Excess water can stop the decomposition process of the manure layer, causing the temperature in the bed to drop quickly. Plants can be destroyed almost immediately by excessive cold.
The cost of building, maintaining, and operating a hotbed can vary greatly, depending on the method of heating used. Manure is by far the cheapest. Electrical heating cable is significantly more expensive. The use of light bulbs as a heat source
is less satisfactory, but also less expensive. However, they can provide a quick and easy way of adding supplementary heat on frosty nights of early spring.
Wood is the most frequent choice of construction material because it is easy to work with and the most flexible if the bed needs to be enlarged or moved. If treated lumber is used, it must have been treated with a non-toxic preservative, otherwise accumulation of fumes in a closed frame can cause plant damage. Redwood and cedar are the woods of choice, since they are naturally resistant to decay.
Wood is the most frequent choice of construction material because it is easy to work with and the most flexible if the bed needs to be enlarged or moved. If treated lumber is used, it must have been treated with a non-toxic preservative, otherwise accumulation of fumes in a closed frame can cause plant damage. Redwood and cedar are the woods of choice, since they are naturally resistant to decay.