This section is from the book "The Gardener V2", 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.
This nut is grown pretty extensively all through Britain, but it is only in the best parts of the kingdom that the fruit ever gets thoroughly ripened. The tree succeeds very well in almost any part of the British Isles, growing as it does to a considerable height, and forming a large and handsome tree. Even in Scotland it thrives very well. There is one large tree here which is a little over 30 years of age, and which is above 40 feet in height, well furnished and healthy, and yearly produces a crop of fruit: as a rule, however, it is only once in two years that it bears a full and heavy crop. During the period I have been here, I have only once seen the fruit approaching to maturity, and that was in the autumn of 1868. The crop was a large one, and a considerable quantity of the fruit ripened, yet those which did were a mere fraction in comparison to those that fell off green.
The propagation of the Walnut is effected by sowing seed in spring, and by budding, grafting, and inarching for the perpetuation of existing varieties. The seed should be preserved in sand during winter in a cool room, and in spring may be planted in light rich soil, in rows 1½ foot apart and 6 inches seed from seed, placed at a depth of 2 or 3 inches. The seedlings may remain in the seed-rows till the second autumn, when they may be transplanted into rows 4 feet apart, and 3 to 4 feet plant from plant. At the end of two years more they may be transplanted into their permanent positions, which, if planted together, must be at least 50 feet apart. The ordinary way, however, is to plant them one here and another there in the best positions in the landscape, so that at once the two purposes are served of usefulness and effect. The only thing necessary, in selecting a position for the Walnut, is to see that the soil is not of too light or too wet a nature. If the soil is very sandy, the best plan is to remove a quantity of it, and have it replaced with good substantial loam. If the situation is wet, let it be drained; and if these two things be attended to, there is little to fear from the want of success.
Budding, grafting, and inarching are seldom resorted to, as there is often great difficulty in succeeding in either operation, from physical causes which it is unnecessary to explain. Inarching the Walnut was first practised by one Boutcher, a nurseryman in Edinburgh. Mr Abercrombie also practised it, as we learn from his works. Mr Knight, who was in favour of budding, wrote a long article in the 'Transactions of the Horticultural Society' regarding it. His remarks are as follows: - "The buds of almost every species succeed with most certainty when inserted in the wood of the same year's growth; but the "Walnut-tree appears to form an exception, possibly in some measure because its buds contain within themselves in the spring all the leaves which the tree bears in the following summer, whence its annual shoots cease to elongate soon after its buds unfold.
To obviate the disadvantages arising from the preceding circumstances, I adopted means of retarding the period of vegetation of the stocks comparatively with that of the bearing tree, and by these means I became partially successful. There are at the base of the annual shoots of the Walnut and other trees, where those join the year-old wood, many minute buds which are almost concealed in the bark, and which rarely or never vegetate but in the event of the destruction of the large prominent buds which occupy the middle and opposite end of the annual wood. By inserting in each stock one of these minute buds and one of the large and prominent kind, I had the pleasure to find that the minute buds took freely, whilst the large all failed without a single exception".
Where grafting is had recourse to, as in France, any of the two following methods may be adopted - viz., whip or cleft grafting. The stock should be cut over in winter at the desired height, and the scions ought to be taken off at the same time and put in somewhere by the heels until wanted in spring. In cutting the stock let it be done just above a shoot, and let the scion be inserted on the opposite side. As soon as the butt of the scion begins to push, pinch the shoot on the stock to check the flow of sap in that direction, and endeavour to throw it over into the graft; and as soon as the scion appears to have taken a firm hold, let the shoot upon the stock be entirely removed. The young tree may after this just be treated as a young seedling, until it is planted into a permanent position. After this little or indeed no pruning is necessary, as, if the tree is left to itself, it is likely to make a finer and equally as productive a tree as if all the arts of pruning were exercised upon it.
The only enemies to the Walnut cultivator are the Zeuzera aesculi, or caterpillar of the wood-leopard moth, and the Cossus ligniperda, or caterpillar of the goat moth, which at times attack the tree, and considerably damage the timber. It is seldom that even these touch it; and when they do, if the tree is a large one, a cure is not easily effected. In the case of small trees, hand-picking and destroying are the best means of getting rid of them. Late spring frosts, extending over a series of years, and injuring the young and expanding shoots, are said to induce a state of debility which eventually ends in the death of the tree. James M'Millan.
(To he continued).