DEPTH AND SPREAD OF ROOT SYSTEMS 141 



gions of the stem is of much service in plant propagation. When 

 canes of some varieties of Raspberries bend over and touch the 

 ground, they become rooted at their tips. If the canes are cut, the 

 rooted tip then becomes a new plant. This is a common method 

 of propagating Raspberries. If the branches of the Grape Vine, 

 or, if many of our shrubs are bent to the ground and a portion 

 covered with soil, roots will develop on the buried portion, which 

 thereby becomes a means of obtaining new plants. Geraniums, 

 Coleus, Roses, and many other plants are propagated by cutting 

 off branches and setting them in moist sand where they develop 

 adventitious roots and l3ecome new plants. 



Depth and Spread of Root Systems.^ — Roots must go deep 

 enough and spread far enough laterally to meet the demands of 

 the plant for absorption and anchorage, both of which in general 

 must conform to the size of the shoot. On this account, trees 

 need a deeper and wider root system than a Corn plant. But 

 aside from these differences which relate to the size of the shoot, 

 root systems of different plants differ in the depth and spread 

 according to : (1) the conditions of the soil in relation to moisture, 

 mineral matter, and air; (2) the type of root system; and (3) the 

 difference in the disposition of the roots of different plants, al- 

 though similar in type. 



Roots, like all other plant portions containing living cells, 

 must have oxygen for respiration. For this reason the region of 

 the soil just under the surface where air is accessible is more fav- 

 orable for root activity than the deeper soil regions. Besides, 

 more of the necessary mineral matter is available in the surface 

 layers of the soil. Consequently, root systems increase by ex- 

 tending proportionately much more laterally than downward, 

 except in cases where there is extensive development of a tap- 

 root, as in such plants as Alfalfa and the Mesquite. 



Studies made of the roots of Corn show that under ordinary 

 conditions the roots extend laterally, most of them being only 

 from 3 to 6 inches under the surface, until they reach a distance 

 of about 1| feet from the plant, and then they extend downward 

 as well as laterally, often having a depth of 3 or 4 feet when the 



1 The Roots of Plants. Bulletin 127, Kansas Agr. Exp. Sta. Root Sys- 

 tems of Field Crops. Bulletin 64, N. Dakota Agr. Exp. Sta. Corn, its Habit 

 of Root Growth, Methods of Planting and Cultivating, Notes on Ears and 

 Stools or Suckers. Bulletin 5, Minnesota Agr. Exp. Sta. 



