8 



BULLETIN 1204, U. S. DEPARTMENT OE AGRICULTURE. 



frosts are typical of the whole Rocky Mountain region and care must 

 always be exercised to prevent excessive frost injury. The best 

 means is to retard spring development as much as possible by the 

 use of shade frames as soon as the buds begin to swell. This pro- 

 longs the period of hardiness. Nevertheless, very late severe freezes 

 are not unknown, and hay and straw must be kept on hand to mulch 

 the beds deeply in such contingencies^). 



Seed-eating rodents, including several species of mice, chipmunks, 

 and ground squirrels, are a source of nursery losses of considerable 

 magnitude throughout the West. 



The white-footed mouse (Peromyscus maniculatus artemi) is the 

 most common of the wild mice and doubtless the most destructive, 

 being active throughout the year. It frequently invades buildings, 

 doing considerable damage to stored forest-tree seed and grain. It will 

 even dig up the newly-sown seed beds at night. The jumping mouse 

 (Zapus princeps) is widely distributed, but the number found in any 



Fig. 2.— Douglas fir transplants (3-2) protected from late spring frost by a mulch of timothy hay applied 

 just prior to the occurrence of the frost, but the tops were injured by a previous spring frost. Cotton- 

 wood Nursery, Utah. 



one place is not large and the damage is less extensive, although not 

 negligible. Several species of meadow mice (Microtus) are found in 

 fields and meadows, where they have regular runways. They are 

 active throughout the year and under cover of the snow cut small 

 seedlings. Chipmunks (Eutamias) are particularly troublesome, 

 devouring and storing away considerable quantities of forest-tree 

 seed. Ground squirrels (Citellus) are also destructive in eating off 

 the newly germinated seedlings. Pocket gophers ( Thomomys) exca- 

 vate tunnels under the beds, depositing the excavated soil in mounds 

 over the beds, and in winter destroy both seedlings and transplants. 

 The practice of screening against rodents was not considered prac- 

 ticable at the nurseries. The nursery grounds were thoroughly 

 cleaned up, brush and tall weeds close to the seed-bed area were cut 

 and burned, and piles of rubbish, lumber, and rocks moved away. 

 In this way, many nests and hiding places were destroyed. Then by 

 a systematic campaign of trapping and poisoning Carried on at the 



