A hot bed is a bed of soil enclosed in a frame that is heated, usually by manure or other methods, to start seedlings for planting outdoors. It allows seeds to be started earlier than planting directly outside. Hot beds are small, low structures that provide controlled conditions for propagating nursery plants and can be used year-round except in very cold winter periods. They provide a cost-effective way to produce large numbers of seedlings for gardens or nurseries.

8. It is a bed of soil enclosed in a glass or plastic frame heated by manure ,
electricity, stream or water pipes. It is used for raising early seedlings.
Instead of relying on outside sources vegetables and flowers best suited
for your own garden can be grown. Seeds may be started in heated beds
before they can be sown outdoors.
These are small low structures used for propagation of nursery plants
under controlled conditions. They can be used throughout the years
except in severe winters.

9.  Another form of hot bed are low polythene tunnels or sun tunnels
made from bent PVC pipe covered with polythene. The standard size of
hot frame is 0.9m by 1.8m.
For small propagation operations, hot bed structures are suitable
for producing large number of nursery plants, without higher
expenditure.