Hotbed

Hotbed, a bed of fermenting vegetable matter, usually surmounted by a glazed frame, employed in gardening for cultivating melons and cucumbers, the rearing of tender annuals, propagating stove and greenhouse plants by cuttings, seeds, or grafting, forcing flowers, &c. It is an inexpensive means for obtaining a high temperature in a limited atmosphere, accompanied with genial humidity charged with nutritious gases, which is very beneficial to plants. Formerly it was an indispensable adjunct to the garden, but the almost universal employment of hot water as a heating agent for horticultural purposes has latterly greatly circumscribed its use. The materials used in making hotbeds are stable-dung, leaves—those of the oak and beech, being especially suitable, are frequently mixed with the dung—tanners' bark, spent hops, and the waste of jute, cotton, hemp, and flax, all of which must be allowed to pass through the first violent stages of fermentation in order to eliminate the deleterious gases they contain before being built up into the bed. The size of the bed is regulated by the degree of heat required for the purpose in view. A bed of stable-dung with or without leaves intermixed, four feet thick, will for some time after it is built maintain a temperature of from 75° to 90°, which is sufficient for most purposes. As the fermentation declines the bed cools down, but heat is again readily increased by adding fresh material to the sides of it. The bed should be made a few inches wider and longer than the frame that is to be placed upon it, and from 6 to 9 inches higher at the back than the front to secure a better angle for light. See also PLANT-HOUSE.