PLANTS FOR MINNESOTA 315 



E. Street Trees. The group of trees (a) given as entirely 

 hardy is interesting for the following reasons: The American linden, 

 here substituted for the European linden — which is of doubtful hardi- 

 ness — is not ordinarily used elsewhere on account of dropping its leaves 

 in late summer when used as a city street tree. The hackberry, while 

 a native of the major part of the United States east of the Rocky 

 Mountains, does not succeed well enough outside of the northwestern 

 portion of its range to enable listing it elsewhere as a street tree. Its 

 natural habitat is rich, moist soil. The white ash is a handsome orna- 

 mental tree native of the eastern United States and not nearly often 

 enough used as a street tree. 



a. Entirely hardy under all conditions: 



Acer saccharum Quercus coccinea 



Sugar Maple Scarlet Oak 



Celtis occidentalis Quercus rubra 



Nettle Tree Red Oak 



Fraxinus americana Tilia americana 



White Ash American Linden 

 Ulmus americana . 

 American Elm 



b. Which should be selected with a thorough knowledge of the condi- 

 tions under which they are to be used: 



Acer saccharinum Populus^ eugenei 

 Soft Maple Carolina Poplar 



Acer platanoides Pyrus ioensis 

 Norway Maple Western Crab 



Betula papyrifera Sorbus americana 



Paper Birch American Mountain Ash 



F. Evergreens Most Used. The group of conifers most used in 

 Minnesota is restricted to a few of the "ironclad" sorts. These are 

 all native species and when used the following notes should be borne 

 in mind. The hemlock is not naturally adapted to windswept places 

 anywhere, and especially not in this region. Of the white fir only the 

 Colorado form should be used, and while this plant will withstand 

 considerable heat and drought it is intolerant of smoke and soot. The 

 arborvitae suffers frequently from ice storms and should be protected 

 from them. The Douglas spruce is one of the fastest if not the fastest 



