10 BULLETIN 392, U. S. DEPARTMENT OF AGRICULTURE. 
uniform in composition, density, and in the amount of heat produced; 
(2) a frame with the rear board 4 to 6 inches higher than the front 
board, and (3) glass or cloth covers for the frame. For a permanent 
hotbed an excavation or pit 24 to 30 inches deep should be made. 
Sowing seed : Sow the seeds in rows 3 to 4 inches apart, one-fourth 
to one-half inch apart in the row, and cover about one-half inch 
deep. Water the surface of the soil with a sprinkling can. Keep the 
hotbed covered with sash or cloth. Raise the sash during the heat 
of the day for ventilation. Water the bed in the morning on bright 
days. 
Cold frame: (1) The uses of the cold frame are (a) the growing of 
vegetables for winter use, (b) the hardening off of the more delicate 
plants in early spring, and (c) starting semihardy plants, as cabbages, 
cauliflower, etc. (2) The points determining the location of the cold 
frame are (a) protection from north wind such as the south side of a 
building, fence, or hedge, (b) nearness to ample water supply, and 
(c) southern or southeastern exposure. (3) Materials for making a 
cold frame are (a) a frame with a board 12 to 16 inches high on the 
north side and 6 to 10 inches high on the south side, (b) glass, canvas, 
or cloth covers, and (c) very rich, thoroughly pulverized soil. 
Study questions : What are the advantages of hotbeds ? How are 
they made? What is the difference between a temporary and a 
permanent hotbed ? Which kind is most commonly used in the com- 
munity ? What plants other than tomatoes are started in hotbeds ? 
Is glass or cloth used for covers ? What is the difference between a 
hotbed and a cold frame ? For what are cold frames used ? To what 
extent are cold frames and hotbeds used in the community? Are 
cold frames used to harden off tomato plants ? What other plants are 
grown in cold frames ? 
References. — Farmers' Buls. 642, pp. 1-3, pp. 12-15; and 460. 
Practical exercises. — (1) Club members and pupils with home work 
should prepare a compost heap under cover and thoroughly rot the 
manure to be used in preparing soil for the hotbed. Manure for 
furnishing Jp.eat for hotbed should be fresh, as well-rotted manure 
does not give off heat. (2) Make frames for the hotbed and for the 
cold frame. (3) Make the hotbed and prepare to sow tomato seed. 
Correlations. — Have the members of the class describe the hotbed 
used in starting their tomato plants. 
Drawing: Draw the frame to scale. 
Arithmetic : If tomatoes are planted in rows 4 feet apart and stand 
3 feet apart in the row riow many plants are required to set one-tenth 
of an acre? If each plant occupies 2 square inches in the hotbed 
what should be the area of a hotbed sufficiently large to produce 
plants to set one-tenth of an acre ? Find the cost of material including 
the cover to make such a frame. 
