FOREST PLANTING IX THE INTERMOUNTAIN REGIOX. 39 



A limited amount of Corsican pine (Pinus laricio corsicana) was 

 planted, sufficiently to show that it was relatively immune to frost 

 or snow-molding injury. 



Oriental cedar {Thuja orientalis) resulted in a complete failure. 

 Northern white cedar (T. occidentalis) was very susceptible to the 

 snow-molding fungi, which resulted in its failure. Incense cedar 

 (Libocedrus decurrens), in one test, showed relative immunity to 

 snow molding, but possessed no other outstanding desirable features. 

 Norway pine (Pinus resinosa) showed relatively poor results, while 

 one-seed juniper (Juniperus monosperma) failed completely. After 

 stratification over winter in sand and lying dormant in the seed 

 bed throughout the following winter, Rocky Mountain juniper 

 (J. scopulorum) germinated abundantly and was grown successfully. 

 This species offers some promise for planting in the oak-brush zone 

 for posts and fuel. White fir (Abies concolor) was grown successfully 

 in the nursery, but is inferior to its associates for use in reforestation. 

 Douglas fir, noble fir (A. nobilis), and silver fir (A. amabilis) 2-0 

 seedlings shipped from the Columbia River region were completely 

 frozen while in the transplant bed. 



European larch (Larix europaea) was easily planted, but the early 

 fall frosts usuaUy killed the new growth and so weakened the trees 

 that the snow-molding fungi killed them all by the end of the first 

 winter. 



The following conifers, tried out to test their frost hardiness and 

 adaptability to intermediate altitudes, were found to be entirely 

 unsuited: Digger pine (Pinus sabiniana), sugar pine (P. lamber- 

 tiana) , and bigtree (Sequoia gigantea) . 



HARDWOODS. 



A number of hardwood species were tested in the Cottonwood 

 Nursery, but none were planted out in the field. At various times 

 seed of the following species was sown: Boxelder (Acer negundo), 

 hackberry (Celtis occidentalis), green ash (Fraxinus lanceolata), 

 black locust (Robinia pseudacacia) , Russian olive (Eleagnus angusti- 

 folia), and Siberian pea tree (Caragana arborescens). These species 

 all germinated well and made good growth; but, with the exception 

 of the last, all were severely injured by the early fall frosts before 

 the new growth had become lignified. In most cases the trees were 

 not killed outright the first season, but repeated killing back for 

 several seasons either resulted in death or rendered them worthless 

 as planting stock. Siberian pea tree, however, is entirely frost-hardy 

 at the Cottonwood Nursery at an altitude of 7,500 feet, where several 

 trees over 5 feet tall are annually producing seed. 



CAUSES OF LOSS AND FAILURE AND METHODS OF PREVENTION. 



UNFAVORABLE SITES. 



Drought is responsible for nearly one-third of all the loss suffered 

 in forest planting in the intermountain region. In the case of ex- 

 perimental plantations it has been the greatest single factor over- 

 shadowing all other causes. Many of the failures can be explained 

 both on the basis of the selection of too arid sites and the disastrous 

 effects of dry seasons. Administrative plantations in particular 



