134 MICHIGAN AGRICULTURAL COLLEGE 



not to exceed five years for each tree so planted and in good, growing 

 condition not less than six feet high and not. less than HO or more than 

 40 feet apart. 



The Michigan Agricultural College and the Public Domain Commis- 

 sion are authorized to raise trees for planting and to sell them at nomi- 

 nal cost to counties, cities, villages, and citizens of the state for highway 

 planting and also for planting in state parks and other public places. 



The Forestry Department of the College 1 has at the present time a 

 considerable number of trees suitable for this purpose. 



Mistakes made in the selection of species of trees for highway planting, 

 may not be discovered in a decade. In order to make such mistakes less 

 common and to safeguard the public against errors in spacing of trees 

 and selection of species for our highways, the Following simple principles 

 are offered: 



1. Use only such trees as are comparatively free from destroying 

 insects and diseases. 



This will eliminate at once such trees as the black locust, the elm, 

 the fruit tree, and any others which may have local enemies. 



2. Use trees adapted naturally to the soil and climate of the locality. 

 For example, a burr oak section should not have 1 its highways planted 



with pine nor should a red pine section be planted to burr oaks. 



3. Pure planting of one species should not be used for distances ex- 

 ceeding one mile. 



4. Use trees that are native to the locality wherever possible. They 

 give quick results and furnish variety. 



5. Along roads that have been entirely denuded of tree growth, plant 

 a temporary and a permanent tree alternately. An example would be: 

 The sugar maple for permanent and the box elder for quick results and 

 removal later when the sugar maple had attained useful size. 



0. Space trees on the highway according to the spread of their crowns 

 at maturity. Taking the sugar maple as an example with a spread of 

 crown of 35 feet from the stem we see that a spacing of less than seventy 

 feet will permit the interlacing of branches, which is not desirable with 

 highway trees; therefore, a safe spacing for sugar maple is 85 feet with 

 trees on the opposite side of the highway to alternate. A planter may 

 determine the safe highway planting distance for any species by measur- 

 ing the crown spread of a fully mature specimen of that species and 

 adding ten feet to the result. 



In general the soil variation gives to the highways of Michigan an 

 opportunity of rare worth for the production of a large variety of trees 

 and shrubs of highly ornamental and utilitarian value. 



