24 BULLETIN 479, U. S. DEPARTMENT OF AGMCULTUTiE. 



SEASON FOB SOWING. 



The season for sowing is largely determined by the species raised, 

 by local climatic conditions, and by experience in nursery practice. 

 If the seed is of a species which germinates slowly, such as western 

 white pine, sugar pine, the Pacific coast form of Douglas fir, or in- 

 cense cedar, heavier and better developed stands of seedlings are 

 usually secured by sowing in the fall than in the spring. Some seed, 

 such as deodar cedar and the true firs rapidly lose their vitality. 

 *For these fall sowing immediately after their collection is also 

 preferable. In most cases species whose seed germinate rapidly 

 can very well be sown in the spring, so as not to be exposed over 

 winter to damage from rodents or subject to the danger of extremely 

 early germination and subsequent killing by late frosts. However, 

 spring sowing, even of such species, is not always thought desirable. 

 Damping-off is less severe, for instance, in fall-sown than in spring- 

 sown beds of jack pine at the Bessey Nursery. 



At the Pocatello Nursery it is thought best to sow in the late 

 spring, because the weather is so cool during the spring that no 

 advantage would be gained by fall or early spring sowing. In 

 Arizona and New Mexico, where the spring of the year is very dry, 

 some of the sowing is deferred until the near approach of the rainy 

 season, which occurs in July and August. Seed sown in these 

 States in the spring requires frequent watering after germination; 

 those sown in the summer do not need artificial watering. Damping- 

 off, however, is less severe there in spring-sown than in summer- 

 sown beds. 



Fall-sown seed have a long period in which to absorb moisture, 

 and germinate rapidly upon the advent of warm spring weather. 

 Watering of the seed beds to induce germination is usually unneces- 

 sary. Moreover, the stock from fall-sown seed is more likely to be 

 fully hardened and able to withstand early fall frosts than that 

 from spring sowing. Stock larger by from one-half inch to 2 inches 

 can be produced in one year by fall than by spring sowing. The 

 increased growth may mean the shortening by a year of the length 

 of time necessary for growing stock to a size suitable for field plant- 

 ing, thus effecting an economy of space in the nursery and reducing 

 the cost of the plants (Pis. IV, V, XV). 



AMOUNT OF SEED TO SOW. 



The optimum number of seedlings per square foot in seed beds 

 varies according to the species, the region (because of the longer 

 growing season and greater development of the stock in some re- 

 gions than in others), the manner of sowing (broadcasting or in 



