Of the remainder of the trees I have enumerated some are slow in growth, which is a considerable drawback; others are not wholly free from being affected by cold winds in the spring or by lice in the winter, and the assistance of an expert is very necessary in selecting trees for this important purpose.
Whatever trees are selected, the following precautions should be taken:
The young tree should have been well nourished in its nursery before removal, and should on no account be planted in the street until its stem is nearly 10 feet in height and about 3 inches in diameter. The stem should be clean and straight, and the whole tree symmetrical.
The great difficulty in this country is to obtain sufficient numbers of trees of the exact size and description, when it becomes necessary to plant out a street. They have often to be imported, when it is found that they are frequently unsuited both for soil and climate, besides being very costly; thus many failures have arisen in consequence. To obviate this necessity in Paris the Government have for many years instituted and maintained special nurseries where trees are grown for this purpose alone, these nurseries being situated at Passy, the Jardin Fleuriste, and Petit Buy, no less than 115 men being constantly employed in the work. Some further particulars will be given presently on the cost of this work.
The trees thus nourished and selected should be planted in the autumn, for there is a well-known saying that “a tree planted before Christmas can be ordered to grow; if planted after Christmas it must be asked to do so”; and there is no doubt that if trees are planted too late in the season great difficulty in getting them to grow is generally experienced.
The excavated pits must be well drained, and filling the bottom of the pit with rubble is a good plan. The further the tree can be planted from the kerb the better, so as not only to give it a larger body of soil, but to lessen the risk of killing the tree by the pollution of the ground with gas from a defective main, and also excess of moisture from the channel gutters. The distance apart of the trees is a matter of choice. In Paris this is only 16 to 18 feet, but I think half a chain (33 feet) is quite close enough; it economises trees and gives plenty of room for the limbs of each tree to spread, and the intermediate lamp-posts, watering hydrants, or other standards are not crowded out.
Each tree should have a cast-iron grating around its roots similar to the following drawing:—
This should be about 4 feet square. It prevents the ground getting hard about the trees, and permits air and water to enter to the roots. It also makes it easy to give any attention to the trees that they may require when young, such as manuring, digging, &c.
The tree should also be protected with a slight iron grill or railing to prevent mischievous persons from cutting their names on the trunk, climbing up into the tree, or breaking off its branches whilst still young. The following sketch shows the description of grill necessary, which is light, cheap, and at the same time effective.