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The Pamphlet Collection of Sir Robert Stout: Volume 84

Part I. — Cultivation of Mulberry Trees

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Part I.

Cultivation of Mulberry Trees.

General Remarks.

This manual is not intended to be a scientific treatise on mulberry trees. It has been compiled for the purpose of giving a few practical hints as to the best methods of planting and propagating those varieties which have been found to be most adapted for silkworm food. It is as yet premature to state which is the very best variety of mulberry for New Zealand. General rules and such information as would apply under all circumstances and in all places would be extremely difficult to formulate, and too vague for practical use at any given point. The following rule may, however, with safety be laid down : All mulberry trees the leaves of which are soft, glossy, and smooth on both sides (not prickly or woolly) may be used. With a first-class quality of silkworm eggs and an equal amount of care bestowed on the worms the difference between one variety of tree and another will not amount to much as regards the quantity or quality of the cocoons.

I have submitted this manual for revision and correction to an expert who has had over twenty years" practical experience in New Zealand of planting and propagating trees. Therefore I venture to hope that the instructions given herein will be found useful and in most instances correct.


The best known varieties of the mulberry tree (Morus) are: Morus rubra, red mulberry; Morus nigra, black mulberry; Morus multicaulis, Philippine mulberry; Morus alba, white mulberry.

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The red mulberry, so called on account of its fruit, which is of dark red colour, of pleasant, slightly acid taste, is totally unfit for silkworm food. As a rule the worms will not touch its leaves.

The black mulberry is planted for the sake of its fruit, which is of black colour, and has a pleasant taste. The leaves of this variety should only he given in case the food from the white mulberry falls short. The worms have great difficulty in eating the leaves, on account of their being prickly. The worms therefore cannot absorb a sufficient quantity of food, they starve, dwindle, and die, or produce a very poor quality of silk. It is not advisable to use the black mulberry at all for silkworm food.

The multicaulis is chiefly used in Asia and Japan, and—although perhaps not so suited as other varieties, being less rich in nutritive elements—it will do very well for silkworm food. It is a shrub, very prolific, and can be easily and quickly propagated by cuttings and layers.

The white mulberry is the traditional food plant of the silkworm. There are a great many varieties : the best known are Morus Moretti and Morus alba rosea (rose-leaved, or Cevennes). The leaves feel soft, smooth, and glossy. The fruit is of whitish colour and unpleasant taste. The wood is yellowish white, and becomes very hard when the tree gets older. The white mulberry often attains very old age, and will grow over 50ft. high. It is easily propagated from the seed, layers, or cuttings, and this last method is perhaps the quickest and most economical of planting to secure a stock. I am informed, however, by nurserymen that it requires a great deal of time and trouble to propagate the alba rosea from cuttings.

Soil, Etc.

Mulberry trees will grow nearly anywhere except in damp, wet soil. Deep, light, rich or sandy soil from which there is natural drainage is the best. The climate does not seem to affect them much. They are found at Christiania, Norway, with a mean temperature per annum of 41° Fahr., as well as at Canton with a mean temperature of 74° Fahr. In very rich soil the trees will thrive remarkably well, but the leaves contain a minor quantity of nutritive elements. Exposure to page 5 the sun and air benefits them. It has been shown that the leaves of mulberry trees grown in the shade contain as much as 25 per cent. more water than those exposed to the sun. Leaves of middle-aged and old trees contain more nourishment than those of young ones under ten years old. Unless the trees are pruned the leaves get smaller every year, and the trees often die. A fact not generally known is, that the roots of mulberry trees grow nearly straight down instead of spreading horizontally. Thus farmers are enabled to grow cereals and root crops in the same field where mulberrry trees stand. This, however, only applies to standard trees at least 10ft. to 12ft. high.

Extended experiments have lately been made in the United States about the value of the Osage orange, and they appear to have been entirely successful. The raiser says, "Very generally used as a hedge-plant in those sections of the country which are particularly adapted to silk culture, its leaves may at once be obtained without any special investment of capital. Indeed, as the hedges need trimming, the cutting-off the new year's growth is a saving rather than an expenditure. Those who use this plant must, however, bear in mind that the shoots from a hedgerow become very vigorous and succulent by the time the worms are in the last age. These more milky terminal leaves should be thrown aside and not used, as they are apt to induce flaccidity and other diseases. In avoiding these more tender leaves and using only the older and firmer ones consists the whole secret of the successful rearing of silkworms on this plant, and if care be taken in this respect there will be no appreciable difference in the silk crop from Osage orange as compared with that from mulberry. The thorns of the Osage make it somewhat difficult to pick its leaves, and I should not advise its cultivation merely as silkworm food. Every year's experience with the Osage confirms all that I have said of its value as silkworm food. Silk which I have had reeled from a race of worms fed on it now for eleven consecutive years is of the very best quality.

Raising Mulberry Trees.

From Seed.—Plants raised from seed turn out more vigorous than from cuttings or layers.

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Where fruit-bearing trees are available collect the berries crush, dry, and put through a fine sieve. Keep the seed in a safe place, as rats and mice are very fond of it. If fruit-bearing trees are not available, apply to a nurseryman, but always ask for Morus alba (white). Seed from old trees is preferable.

Sow in the early spring in deep, rich, light, soil, if possible in a sheltered place. If in an open place, stick branches of ti-tree or other scrub in the ground, to protect the seedlings from the fierce rays of the sun in the late spring. Towards autumn the branches may be removed. Sow in rows Gin. apart, about ½in. deep. Cover, rake, and beat gently with the hack of a spade. If the seed is soaked in water for two or three days before sowing the seedlings should make their appearance in about three weeks; at the end of the first year they should be about 12in. high.

Some time during the first winter they are lifted from the seed-bed and planted into nursery rows about 18in. apart, and the young plants about 9in. apart. Before planting, cut them back to about 4in., and when planting cover the roots about the same depth as they occupied in the seed-bed.

If the seedlings are left without cutting back they will produce too many branches, making it more difficult to train them into proper shape later on, when they are set out into permanent position. If only two or three eyes are allowed to grow, these will in time become strong, sound branches, giving a better opportunity, the following season, of raising a well-built tree. This method is somewhat slow, but raisers will find it to their advantage to raise high-stemmed trees, because the older the tree gets the more leaves it will yield, until as much as lewt may be got from one tree. This does not apply to Multicaulis, it being a shrub. During the growing season keep free from weeds.

At the end of the second season the young trees should be about 3ft. or 4ft. high. At Home the seedlings leave the nursery after the third year; in the northern part of New Zealand they may be set out after two years—that is, in the spring of the third year. Never transplant without pruning off all jagged ends of the roots.

When planting out in permanent positions plant them the page 7 same depth as they were in the nursery bed. If intended to raise dwarfs, 10ft. apart, if standards, 15ft.

Dwarfed trees are preferred by many people because it is easier to gather the leaves, but of course they do not yield the same quantity as full-grown high-stemmed trees.

Trees should be pruned every year; the best time is after the silkworm season is over, or in spring, when the leaves make their appearance and the silkworm eggs are hatched, so as to be able to use the leaves on the cut-off twigs for food.

In pruning train the head in the shape of a cup, causing the branches to come out horizontally from the stem, so as to give space in the centre for free admission of light and air. It will also facilitate the gathering of leaves.

Grafting.—Some people have found it advantageous to graft the white on to the black mulberry, the latter being hardier.

Layering.—Mulberry trees can very easily be propagated by this method, which requires no further explanation. Hedges may be formed in this way.

Cuttings.—Plant cuttings in rows 4in. apart, in well-dug ground. They should be about 9in. long, with two or three eyes at the top of each cutting. The rest of the eyes are rubbed off. Bury them about Gin. in the ground. The second season treat them like seedlings.

The height of the tree and its shape are easily regulated by pruning, and upon this process depends not only the vigorous growth of the tree, but also the ease with which the leaves may be gathered when wanted. All dead twigs should be removed, and the limbs kept as smooth as possible.

The best times for planting are the months of July and August.

Enemies and Diseases.

Cattle, sheep, goats, hares, and rabbits are very fond of the leaves and twigs. Slugs and snails eat the buds as they burst, and if not looked after will destroy numbers of plants, especially seedlings. Sprinkle lime over the seed-bed or cuttings after dark, when the grubs are feeding. This must be done frequently, as the lime soon loses its killing powder. Attention need page 8 only be given to the above during the earlier stages of the plant's growth.

Borer.—This insect is very common. It seems to he particularly fond of mulberry trees. Branches attacked by the borer should be cut below the extremity of the burrow, and destroyed (burnt). Probing the galleries with wire has been found effectual. Some people inject soapsuds, mixed with a little carbolic acid. If the roots penetrate into cold, wet soil

Foot-rot may be caused.

Blight is less frequent. Where it makes its appearance castor-oil, mixed with a little soot, should be applied with a brush.

The chief points to keep a mulberry tree healthy are—Plant in dry, light, well-drained soil; do not allow any useless growth; do not allow the branches to interlace; admit plenty of light and air, so as to give as little cover to insects as possible; remove primings, moss, and lichen from trunks and branches; keep ground clear from grass and weeds.