Generally speaking, the materials with which roadways are made are not only unsuitable for tree cultivation, but positively destructive to vegetation of almost every description. This also applies to our squares, terraces, and open grounds around houses, the soil of which is little other than refuse building materials, and mainly composed of broken bricks and stones, gravel, old mortar, iron, wood, and shavings. In such a medium it is perfectly useless to look for that healthy and vigorous growth which is so essential in street trees, that are still further handicapped by having to do battle above ground with the impurities of a town atmosphere. Having for a number of years had to plant trees and shrubs in many parts of London, it was found that in nearly every instance substituting good soil for that found naturally was a first necessity. Many failures in street planting from this neglect of providing suitable soil could be pointed out, the result being that a section of the public has become tired of the subject in consequence of the initial expense and subsequent failures. Too often, also, the important operations of preparing the ground and planting the trees are left in the hands of the surveyor or builder, who has little or no knowledge to fit him for the work, the operation being carried out by labourers who are also perfectly ignorant of what is required or the conditions necessary for successful tree and shrub culture. The consequence is that failure is almost certain, and the trees which were strong and healthy when planted gradually become unhealthy and ultimately succumb to a combination of circumstances which were brought about by the ignorance of the operators.

Another source of failure in street planting is the generally pent-up condition of the roots, for in several cases that have come under our notice lately the planter seemed to think that it was quite enough to cut a small hole in the pavement or street of sufficient size to hold the roots of the tree to be inserted. Were the soil free, as we find in a field, this system might answer; but where the roadway is hard as iron and composed mainly of clinkers and gravel, the case is totally different. Another fruitful source of failure in street planting is placing the pavement in too close proximity to the stem of the tree, and numerous instances could be pointed out where even old and established specimens have suffered irreparable damage in consequence of having the paving brought up too close to the stems.

The roots should always be allowed plenty of breathing room, and to effect this a good-sized space should be railed off around each tree and no pavement laid within it. Gratings may be placed on the surface of the ground around the tree, should circumstances compel such a course. By adopting either plan, a double benefit to the trees is brought about by allowing free access of water to the roots and preventing an accumulation of noxious gases in the soil, as would be the case if the flagstone or pavements were used.

Where street trees are to be planted, the ground surface should in every instance be thoroughly broken up for a space of not less than 8 ft. square, and to a depth of, say, 4 ft., the inferior soil removed and replaced by that of good quality, preferably of a loamy description, or loam and leaf soil in about equal proportions. Before placing the fresh soil in position, the sides and bottom of each pit should be thoroughly loosened with a pick or fork. By undermining the sides of each pit, a much larger and freer root run will be provided, and this will not occasion so much of the street or pavement to be torn up as if the pits were of equal width at the top and bottom. We have found, in London at least, that the addition of a small quantity of leaf soil to the loam is highly beneficial to the growth of trees by retaining dampness and encouraging root spread. The newly added soil should be firmly trampled in the pit before planting is engaged in. Sometimes, where the original soil is not of too inferior quality, a small proportion has been mixed amongst the loam and leaf soil, but, speaking generally, this course cannot be adopted.

In squares and gardens where shrub-planting is to be engaged in, a general renovation of the soil is also imperative, and this can best be done by thoroughly trenching the soil to a depth of, say, 4 ft. and adding a large proportion of fresh loam or other soil. Deep trenching and thoroughly breaking up and loosening the soil is a most important factor in town planting, and should never be neglected. Manure is sometimes added to the soil, but it is objectionable from several points of view, and, if used at all, should be thoroughly decomposed and incorporated in small quantity. Good loam and leaf soil is infinitely preferable, and, where necessary, sandy soil makes a good addition. A little fresh lime added to the soil has been found most beneficial in town planting, and in old and exhausted borders, where the soil has become tainted with chemical impurities, the value of lime or chalk as a cleansing agent is not sufficiently appreciated. Of course, where so-called American shrubs are to be planted - which is, however, rare in London - neither chalk nor lime should be added to the soil. This question of soil is so important that no one planting street trees or shrubs can afford to ignore it, and while the extra cost in providing such is but little, the advantages gained are great.