This section is from the book "The Gardener V1", by William Thomson. Also available from Amazon: The New Organic Grower: A Master's Manual of Tools and Techniques for the Home and Market Gardener.
Nothing beats good gravel walks. They look better than any other when well kept, and "look" is not the least important consideration in a garden. They entail an amount of keeping, however, which could generally be well dispensed with, not to speak of the fact that gravel is not to be had in many parts of England except at an extravagant price. This is the case with ourselves, the nearest approach to gravel we can procure being a kind of shale out of the coal-pits, which, after being burnt and broken up, is of a light brick colour, assuming, after exposure to the weather, a more subdued and respectable grey tint, suiting pretty well for pleasure-ground walks, where the traffic is light, but, from the softness of the material, wholly unfitted for the kitchen garden. In this department we are therefore obliged to resort to asphalting, a plan which was favourably noticed by the Editor of the 'Gardener' some time ago in his notes on the gardens around Manchester, and which I propose to describe for the benefit of those who may be disposed to try it themselves, without going to the expense of employing regular asphalters, who in this district charge, I believe, from 8d. to 1s. per square yard, finding all the materials.
Those, of course, who want a very neat job should employ them; but for all practical purposes, good walks may be made by common labourers, as is done here. Asphalt walks are easily and cheaply made, are neat and durable, require no weeding, and, as far as my experience goes, are perfectly safe as regards injury to the roots of trees, etc, of which more anon. The materials - gas-tar and ashes - are easily procured, both being often to be had on the establishment. Ashes, at least, are always plentiful about a garden, and the tar is generally to be got cheap at the nearest gas-work.
Operations for asphalting commence in winter. In wet or frosty weather, when other work cannot be carried on, the men are set in some out-of-the-way place to screen a quantity of ashes, using a 1-inch barred screen or sieve. The ashes are afterwards laid up in a heap; the tar is brought and stored conveniently near; and both are left till about the month of April, which is the best time for asphalting, as there is less danger then of severe frosts occurring to break up the "cake ' before it is thoroughly set, and it also gets time to harden before the heat of summer sets in.
Supposing, therefore, that the walks are cut out, the bottoms filled up with rough ashes or other material to within about 3 inches of the desired level, rolled firm, and the edges of stone or box laid, commence to prepare the asphalt as follows: A clean space having been made near the large heap of sifted ashes, two men set to with shovels, by taking about two barrowfuls from the heap and spreading it in a circle, about 3 or 4 inches deep, a little to one side. The tar is then lifted out of the tubs with a long-handled ladle, and poured over the ashes until they have just got sufficient to soak them without any going to waste by draining away. Then, much in the same way as a mason's labourer mixes mortar, the ashes are turned quickly over once or twice, the better to soak them, and again laid a little to one side as the foundation of the heap. Another similar quantity of ashes is again drawn from the large heap, soaked and turned in the same manner, and thrown on the top of the first; and so on, until the whole is finished and thrown up in a conical heap. This is the first stage. The heap is now allowed to stand for about ten days, or longer if the walks are not ready.
By that time the ashes will have absorbed the tar thoroughly, and will appear to be much drier than at first, when the same operation of turning the heap by small quantities at a time, and soaking with tar, is again repeated as before, the object being to add just sufficient tar to make the ashes "sticky," without making a puddle of them. The evil of too much tar is, that the walks are soft, and the tar comes up to the surface in the rolling. For this reason it is better to leave the heap to drain for a week or so after the second turning also. This much being accomplished, and supposing all to have gone right, it will now be time to make the walks. Some fine morning, and when there is a prospect of the weather being dry for a day or two, all the barrows are put in action. Two men are set to fill, with strict injunctions to take the heap straight forward as it comes, as the ashes are always wettest in the centre of the heap and driest at the sides; and two are set to spread the asphalt on the walk as it arrives, about 3 inches deep, with iron rakes, using the back or teeth of the rake as may be needful, and taking care to have the walk slightly round in the middle.
Putting on and spreading the asphalt does not take so long as might be imagined - six or eight men will cover 100 yards of walk, 6 feet broad, in about three hours. After spreading, the walk is then rolled with a heavy roller, two men pulling it slowly along, and one going behind sweeping the asphalt off with a besom as it sticks to the roller, whose duty it is also to wash the roller at the end of each journey. After being rolled for an hour or two until it is middling firm, the walk will be ready for sprinkling with the spar or gravel. Whatever material is used it should be got ready beforehand. We use Derbyshire spar mixed with shale, which gives the walks a clean smart appearance; but common river-gravel, put through a 1/2-inch sieve, would do well, and would give the appearance of a smoothly-rolled gravel walk. The spar is sprinkled on regularly with the hand, and just thick enough to hide the black surface of the asphalt, then rolled in with the roller until the walk is smooth and firm, when it is finished and fit for traffic.
It should, however, be rolled for three or four mornings in succession, before the sun gets strong, in order to insure a firm "set".
The objections which have been urged against asphalt walks for gardens are, that in hot weather the tar smells disagreeably, and that it is injurious to box-edgings and the roots of trees. As regards the smell, it soon almost disappears, and even in very hot weather it is never so perceptible as to be in the least disagreeable. Box does not thrive very well if it has not got established before the walks are asphalted; but I could point to walks in the garden here where it thrives as luxuriantly as could be desired, although they have been down in asphalt for years. We are, however, replacing the Box with imitation stone-edging, which is neat and substantial, and resists the hardest frost, harbours no vermin, saves much labour, and is in every way superior to Box for the kitchen-garden. It is manufactured in Hull, and sold at 8d. per yard. As far as my experience goes, I can certify that no harm need be apprehended to the roots of fruit-trees, as I have often seen suckers from their roots force their way through decayed or soft places in the asphalt in abundance; and I could at this moment show the roots of Vines in healthy action under walks that have been asphalted several times since the Vines were planted.