This section is from the book "The Gardener V3", 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.
The Filbert, which is just the common Hazel-Nut of the woods in a cultivated state, is not in very general cultivation throughout Britain, although it has been indigenous therein for a very long period. It is, however, more cultivated in the southern counties of England, especially Kent, than in any other portion of the British Isles. In the north of England and in Scotland the Filbert is only cultivated in some of the more extensive places, and that in many instances more for the name of the thing than for the sake of the yield of crop. In the south of Europe, and more especially Spain, this forms an article of commerce of considerable importance, the export trade from some of the Spanish ports being very large. The Nuts imported from Spain are decidedly superior both in flavour and size to any grown at home. This is to be accounted for from the fact that the soil of Spain is very well adapted to its cultivation, and that with a brighter sky and a longer summer the Filbert is more thoroughly developed and better ripened than it is ever possible to obtain it in this country.
There are several varieties of the Filbert in cultivation - M'Intosh, in bis 'Book of the Garden,' enumerating eleven sorts, while in Thompson's' Gardener's Assistant' there are described twelve d ifferent kinds, all of which are highly recommended as well worthy of cultivation. The propagation of the Filbert is effected either by seeds, suckers, layers, or grafts. Like everything else where new and improved kinds are wanted, this can only be accomplished by the sowing of seed. For this purpose the finest Nuts should be selected from the varieties from which it is intended to raise seedlings. The Nuts should be sown in autumn in lines 1 foot apart, and from 3 to G inches seed from seed. The lines may be about the usual depth made for Peas; and as rats and mice are very apt to attack them in the seed-bed, the best method to repel their advances is by thoroughly rubbing every Nut over with a thick coat of red-lead at the sowing period. "When the seedlings have arrived at one year old, they ought to be transplanted into lines 2 to 3 feet apart, and 1½ to 2 feet plant from plant in the row. They may remain in these lines for 2 or 3 years, according to the progress they make, and by the end of this time they should be ready for their permanent position.
When the seedling comes up it ought to be trained as straight as possible till it arrives at the desired height at which the head is to be formed. Some grow dwarf-stemmed bushes, others tall-stemmed, but 3 feet we would consider a very good height at which to form the head of the tree. Should the seedling make a good growth of 4 or 5 feet, then at the transplanting time let it be cut back to the height indicated, and let all buds be removed except four or five at the top. These buds will in all probability all start into growth the following spring. From these, then, the head may be formed much in the way we have already recommended for the Apple and Pear. It is very seldom, however, that the Filbert is propagated in any other way than by layers. The late Professor Lindley considered the propagation of Filberts by layers not only to be the easiest of accomplishment, but also to be the best and most rapid means of obtaining established young trees. Regarding this matter he observes: "If the laying them down has been properly performed, the layers will be well rooted by the end of the year, when they should be taken up and planted into nursery-rows 3 feet apart, and 1 foot from each other in the rows.
Previous to their being planted they should be pruned, leaving only one, and that the best shoot, shortening it to 1 foot or 18 inches, according to its strength. As the plants grow up they should be trained with single stems of 18 inches to 2 feet high, which will allow room to clear away any suckers the plants may afterwards produce." Suckers do not answer nearly so well as layers, because we find layers produce better stems than suckers, and they are not nearly so apt to produce suckers again. It is by layers that nurserymen generally produce their young stock of trees where they have respect to the quality of their stock, but where quantity is more an object than quality the general practice is by suckers. The soil best suited for the growth of the Filbert is a good medium yellow loam, more inclined to be light than heavy, and if containing a large amount of vegetable matter, so much the better. If there be a deficiency of this in the loam, it may be added in the shape of leaf-mould, or suchlike. While the Filbert likes a soil rather moist than otherwise, it must at the same time have good drainage. If it lacks good drainage, then let the cultivator at once have it attended to.
The best position for the cultivation of the Filbert is in the orchard, where it may be planted in any position well exposed to the sun, and yet where it may be sheltered to some extent from the withering blasts of winter, and especially early spring. "The boundary of an orchard," says Mr M'Intosh, is a very proper place for a plantation of Filberts, and if well managed will give an abundant and useful return. Much, however, depends on a proper selection of sorts and on a judicious mode of cultivation - two matters very seldom thought of. The best time for planting the Filbert is in autumn, any time from the beginning of September. October is perhaps about the best month of the whole year for performing this operation, although it may be done at any time the whole season till the middle of March. If the tree seems over-luxuriant, let it be root-pruned and managed in every respect as has been already recommended for the Apple and Pear. As the Filbert is not a large-growing tree, from 10 to 12 feet will be found quite sufficient distances at which they may be planted apart. The Filbert is seldom in a fruitful condition until it has reached the age of eight or ten years.
The Filbert being monoecious, it is generally found that young and vigorous trees produce a preponderance of male flowers, while old trees are very apt to be the reverse. The female flower is very small, and of a bright pinkish colour, while the male flowers are easily recognised by their pendent catkins, from 2 to 4 inches long. Where these catkins are awanting on the trees let an examination be made, and if there are plenty of female flowers thereon let a branch with male flowers be cut and hung in the centre of the tree so soon as the pollen appears ready for fertilisation. As the female flowers are mostly produced upon the points of the branches, it is a good plan to take a bunch of male flowers and draw them gently over the surface of the bush any time when the pollen is in a dry condition.
So far as we are aware, there is no disease which attacks the Filbert to any great extent in this country, and the only insect enemy known to do the crop injury is the Balaninusnucum, which pierces a hole through the shell of the Nut while yet in a young state, and deposits an egg into each cavity made. Here is hatched a maggot, which, as soon as it springs into active life, devours the kernel of the Nut. After the Nut is finished it eats its way out and buries itself in the ground, where it remains all winter, changing in spring to a chrysalis, from which at length is produced the perfect weevil. The best method of destroying these pests is by shaking the trees about the end of August, when those Nuts which have been attacked will be easily recognised by the hole in their shells, and which must at once be taken up and burned, so as to destroy the enemy.