Two of the major considerations for growing plants in a greenhouse environment is keeping them warm and preventing disease in the enclosed environment. Manure may play a factor in both processes. Manure has long been used to heat plants. Ancient Romans used manure as a heat and compost source in early greenhouses. Composting manure releases heat that can be used to mature plants early in hotbeds, while the composted manure may be mixed with peat moss to form a disease-free alternative to soil.
Dig a trench for your hotbed that is 14 inches deep and 3 feet square.
Pack the hotbed 10 inches deep with manure.
Layer 4 inches of a loamy soil mix, such as peat moss, over the top of the manure.
Cut a 2-by-6 foot board into six boards that are 3 feet long. Cut one of the 2-by-6 boards in half diagonally from corner to corner to form 2 triangles. Cut a 2-by-2 into two boards measuring 6 inches and two boards measuring 12 inches.
Place 4 2-by-6s at right angles to one another to form a box. Place the longer 2-by-2 boards in the corners of the box on one side and the shorter 2-by-2 boards in the corners on the other side. Nail the 2-by-6 boards to the 2-by-2 boards to form a box with two corner brace boards sticking up 6 inches above the box.
Place the remaining 2-by-6 against the two corner brace boards, and nail it to the boards.
Fit the triangles to the sides of the box, and nail them in place.
Place a window over the top of the box and nail the window sash in place. Position the hot box over the manure trench. Turn the box so it faces south.
Remove the loam and manure and mix them once you have finished using the hot box to start bedding plants. By now, the manure will be composted and will no longer heat. It will be disease-free and suitable for putting into containers for plants.
Mix equal parts loam, manure and sand to create a soil-free mix suitable for greenhouse use.
Scoop the mix into containers or raised beds using a hand trowel or shovel. Create planting pockets in the mix for bedding plants. The planting pockets should be twice as wide as the root ball of the bedding plant. Place the plant in the planting pocket, and fill in around the sides with the soil. Water well to help establish the roots of the plants. The manure mix should remain as damp as a wrung out sponge.