8 MISC. PUBLICATION 4 3 4, U. S. DEPARTMENT OF AGRICULTURE 



Ordinarily, seed should be collected and the progeny planted within 

 the same zone. 



Where absolutely necessary, it is considered permissible to move 

 seed or stock from one zone to the adjoining zone but no farther, 

 except in a few rare cases where altitude or other factors compensate 

 for the latitudinal gap. For instance, it is possible to move blue 

 spruce safely from the higher western part of zone G or H, to A, or 

 to move seed of western white spruce from the Black Hills in western 

 South Dakota to lower sites in zone A in the northern half of North 

 Dakota. Seed of the native hardwoods on the prairie-plains should be 

 collected preferably within 50 to 75 miles of where the trees are to 

 be planted. 



As a general rule, using northern seed in the south is not particularly 

 dangerous but is likely to give trees of slow growth and poor develop- 

 ment or trees which may eventually succumb to drought and heat. 

 It may result in frost damage to the new growth if the northern 

 stock buds out on the first warm days of spring. When southern seed 

 is used too far north, the elimination of the progeny may occur much 

 more promptly, since they lack the hardiness and early ripening of 

 wood, etc., necessary to withstand the northern winters. 



The danger of the south-to-north movement was illustrated by 

 an experiment conducted by the Lake States Forest Experiment 

 Station (table 2) . Sixty-nine lots of seed of green ash, collected over 

 the region from North Dakota to Oklahoma in 1934, were sown in 

 northern North Dakota in the spring of 1935. Counts made in the 

 fall of 1935 and again in the summer of 1936 to determine overwinter 

 survival of the various lots (table 2) indicated extraordinary low 

 survival from southernmost seed, despite its very favorable germina- 

 tion. 5 It is believed that after a few years the trees from farthest 

 south will virtually disappear. It has been found by the Forest 

 Service that a northward move of 50 to 100 miles near the northern 

 limits of a species' natural range may result in much more winter 

 injury than a similar move near the center of the species' range. 



Table 2.— Overwinter survival of green ash from different latitudes, 

 sown in North Dakota 



Source of seed 



Lots sown 



Seedlings, fall 1935 







Per lot 



Total 







Number 

 25 

 12 

 21 

 8 

 3 



Number 

 12 

 44 

 43 

 30 

 44 



Number 

 294 

 532 

 013 

 241 

 132 



Number 

 197 

 330 

 438 

 94 

 9 



Percent 



fi7 



South Dakota. . . 



62 



Nebraska 



48 

 39 



Oklahoma 



7 



When the same seed lots described above were sown in a Nebraska 

 nursery, midway in the range of the entire group, much less difference 

 was evident (table 3), although the stock of North Dakota seed again 

 survived the severe winter of 1935-36 slightly better than the others. 



Movements from east to west — that is, generally from moister 

 to drier climates — appear less harmful but should not be encouraged. 



s This is a fairly usual experience, although favorable germination is a common excuse for collecting seed 

 in the warmer regions. These sowings were expected to produce 500 seedlings each, but most of the seed 

 produced in 1934 was of poor quality and this seems to have been especially true of the North Dakota lots. 



