148 MASS. EXPERIMENT STATION BULLETIN 170. 



Such trees as the balm of Gilead and Itahan pophir possess extensive 

 root systems. This is evident from the root suckers which may fre- 

 quently be seen coming up quite a little distance beyond the spread of 

 the branches, and many roots will grow in a horizontal direction to great 

 distances. There is an authentic case of an elm whose roots were found 

 in abundance 75 feet from the trunk, — just the height of the tree. In 

 another case the roots of an elm were found obstructing drain tile which 

 was 450 feet from the tree. The leading roots of a pear tree developed 

 in 60 feet of a line of drain tile during five years measured 8,498 feet 

 (1.61 miles); if smaller roots be included, the total length was about 2 

 miles. A squash grown in a greenhouse produced in a few weeks a total 

 of 15 miles of root growth, or over 1,000 feet of roots per day. 



Ohstruction of Sewer Tile, etc., by the Roots of Trees. 



The obstruction of sewer services and drain tile by tree roots has in 

 some places become such a nuisance that steps have been taken in certain 

 cities to obviate it. The elm is a troublesome tree in this respect, often 

 completely filling land drain tile for long distances with roots, and putting 

 the tile out of commission. 



The Carolina poplar is a more troublesome tree, however. This causes 

 so much damage to house sewer connections that its use for planting 

 has been discontinued in some sections. The Carolina poplar is a tree 

 of such rapid growth that an extensive root system is developed in a 

 short time. Sewage appears to have an especial attraction for the roots 

 of tliis tree. They seem to have no difficulty in penetrating even the 

 cement joints of Akron tile, and when once in the tile the root develop- 

 ment is remarkable. In one city as many as eighteen sewer services had 

 to be taken up and repaired in one month the sections were so badly con- 

 gested with roots of the Carolina poplar. Other tree roots occasionally 

 enter tiles, cesspools and wells, but the Carolina poplar appears to be 

 the greatest offender in this respect. 



From the results of numerous experiments covering a period of years 

 it is evident that roots can be kept from penetrating drain tile by properly 

 packing the joints with chemically treated fibers, which destroy the 

 delicate roots as they attempt to enter. ^ 



Branching Characteristics. 



There is considerable difference in the branching habits of trees. This 

 must be understood before a tree can be developed along desirable Unes. 

 The red and Norway maples have a habit of sending out large branches 

 or secondary leaders at more or less oblique angles, very close to the 

 ground. If allowed to develop, these render the trees undesirable for 

 street use; but if started right when young by pruning, such trees may 

 be trained to meet the requirements of residential streets. However, 



iMass. Agr. Expt. Sta. Rpt. 23, Pt. 2, p. 35 (1911). 



