42 CIRCULAR 421, U. S. DEPARTMENT OF AGRICULTURE 



of 2.5 to 3 inches in the block spaced 4 by 8 feet. As in previous 

 tests, this species has proved to be the most hardy of those tested. 



HOG-HOUSE SHELTERBELT 



The hog house at the field station was located to the north and west 

 of the other buildings in a comparatively exposed position. To pro- 

 tect this house a shelterbelt consisting of three rows of Chinese elm, 

 three rows of Eussian-olive (Elaeagnus angusti folia L.), and one of 

 honey locust (Gleditsia triacanthos L.) was planted in 1925. A severe 

 freeze in September 1926, before the trees had ceased growth for 

 the season, caused partial killing of the young elm and Russian-olive 

 trees. Conditions were favorable the next spring, and these trees 

 made a rapid growth, but the character of the growth was bushy 

 because of the killing of the top branches. 



The killing back causing a bushy growth resulted in this becom- 

 ing the best snow catcher of any belt on the farm, entirely eliminat- 

 ing snowdrifts from the hog house and farrowing pens. The large 

 amount of snow held by the belt gave the trees additional moisture, 

 which has been very clearly reflected in the resultant remarkable 

 growth. 



The Russian-olives, since 1926, have shown little winter injury, ex- 

 cept for certain trees whose smaller branches have been killed. Chi- 

 nese elms showed little winter injury from 1926 to 1931. In the 

 spring of 1932 a few elms were found to be entirely dead, and many 

 others had dead branches. 



Honeylocusts have survived fairly well, but have been very poor 

 trees for shelterbelt purposes. They have few branches near the 

 ground, and as a result are valueless as snow catchers. This species 

 should be planted in interior or leeward rows where it will serve 

 for wind-protection purposes, rather than toward the windward side 

 where the chief function would be to hold drifting snow. The use of 

 the thornless variety is recommended for shelterbelts. 



CONCLUSIONS FROM SHELTERBELT INVESTIGATIONS 



The accumulated results to date indicate that shelterbelt plantings 

 should be restricted to a few species of hardy trees. Low-growing 

 bushy species to check snow should form the border rows on the 

 north and west. Siberian pea-tree and Russian-olive are adapted to 

 this purpose. Ash and American elm have proved to be the best 

 adapted of the taller-growing species, with ash the most hardy of the 

 two but having a slower growth rate. Chinese elm has also given good 

 promise, and its rapid growth rate makes it a valuable species for 

 use in a windbreak where quick protection is desired. They should 

 be planted with full understanding that they may not be fully hardy, 

 and that in time they may be eliminated. By the time the Chinese 

 elm has killed out, the ash and American elm should have reached 

 a height sufficient to check the wind in the immediate vicinity. 

 Northwest poplar also has a rapid growth rate and can be used as 

 a temporary tree on the more favorable sites. Where rapid growth 

 and a good survival is desired over a period of years, the Chinese 

 elm should be used in preference to Northwest poplar on all sites 

 except those which are very favorably situated in relation to moisture. 



