CHAPTER III
PROPAGATING TREES AND SHRUBS
There are several methods of propagating trees and shrubs: such as by seed-sowing, from cuttings or layers, and by budding and grafting.
=From Seed.=—This natural process of reproduction is that most commonly adopted where large numbers of trees are required—indeed, certain species, particularly of the Coniferæ, cannot successfully be raised in any other way. The preparation of the seed-beds is a point that deserves far more attention than it usually receives, and that not only on economic grounds, but in view of the general appearance of the nursery borders as well. To tumble the seeds indiscriminately into the ground as if they had fallen in showers from the trees is highly objectionable; and just as censurable is the too-oft-repeated practice of sowing these in rough, cloddy, and ill-prepared ground.
Systematic arrangement in the laying out of the beds, as to the number and requirements of the future seedlings, should also be attended to.
The ground intended for seed-beds should be trenched or deeply dug up; but this operation would, for the mellowing and cleaning of the soil, be better performed the autumn before than at the time of sowing down.
In any case, just before sowing, the ground should be carefully turned over, all hard clods being broken down, and large stones raked off, the surface soil to the depth of 3 in. or 4 in. being made as fine as possible. Dry weather must be chosen for the formation of seed-beds, as also, indeed, for the sowing of the seeds. The beds are marked off and prepared as follows:—A light, strong line is stretched along the ground at, say, 3 ft. from the boundary fence or path, and, after being fixed at each end, the first alley, or path, is marked out by treading the soil alongside of the line. The length of the bed thus marked off on one side is quite immaterial, but the width is of great importance, and should never exceed 4 ft.; 3 ft. 6 in. is nearer the mark.
Adjoining this first line, a bed the above width is marked off with a peg or stake at each end, the line reset and a second alley marked off. The alley, or path, between each couple of beds need not exceed 15 in. in width, this being for the sake of convenience in sowing, weeding, watering, shading, and otherwise attending to the bed, and its occupants. Outside this follows a second bed, and so on, until the desired number has been formed. Some persons raise the seed-beds a little above the level of the paths, but, except in very retentive or damp soils, this is not to be recommended. The beds should in no instance, however, be below the level of the paths. There are two methods employed in opening up and preparing the beds for the reception of the seeds either of which, if carefully gone about, is well suited for the exigencies of the case. My own way has always been to level and smooth the surface of the bed with a small-toothed rake, and after sowing the seeds to cover lightly with fine soil and ashes carefully sifted over the bed by means of a small-meshed riddle. This plan has many advantages, not the least important being the covering of the seeds to an equal depth, and the employing of only the finest class of soil. The other method is by using what is termed a “cuffing-board”—that is, a board about 8 in. wide, placed on a handle, which is inserted in the centre, towards the back, the handle being fully 5 ft. long. A skilled person is required to use this tool, who stands in the alley, first on one side of the bed, and then on the other, pushing or drawing towards him from the surface of the bed a thin coating of soil along its full length and from about two-thirds of its surface.
As to the amount or depth of soil taken off, this is regulated by the particular kind of seed to be sown, as well as the nature of the soil.
The next matter, the depth at which the seed should be sown, is one of great importance. Usually seeds are sown unnecessarily deep. In the majority of cases a safe guide is to place the seed, of whatever kind it may be, about three diameters below the surface of the soil. The conditions most favourable to germination are moderate dampness, abundance of air, and a temperature of about 45°. In order to ensure these conditions, the depth at which the seeds are placed will be seen to be of the greatest moment. Generally speaking, the less seeds are covered, consistently with their receiving a sufficient supply of moisture, the better, and but for their destruction by birds, many of the smaller seeds would vegetate just as well if cast upon the ground-surface, and pressed in, as by being covered with soil. The following interesting experiments with Scotch fir seeds have been made:—
“Those buried one-fifth of an inch came up first, but were subsequently less vigorous—they soon, however, acquired vigour;
“Those covered from one-third to one-half of an inch came up more slowly, but evenly and strong;
“Those buried from two-thirds of an inch to one inch came up in deficient numbers; and
“Those buried from one to two inches never showed any signs of germination.”
These statements are equally applicable to the sowing of seeds in general but especially if their relative size and the hardness of their covering are taken into account.
Immediately after the bed is prepared the seed should be sown, the amount used varying according to quality, which latter may readily be tested by examining the embryos of a dozen seeds picked up at random from the heap. To ascertain whether seeds are good, the simplest way is to cut the sheath open with a sharp penknife, when the kernel ought to completely fill the entire coating or shell. Small seeds might be crushed by the nail, and if good, will leave traces of moisture or emit an odour of turpentine. Another method is to place, one after the other, say a dozen seeds taken at haphazard from the heap, on a red-hot iron. If good they will turn about with a cracking report; but if otherwise, combustion is slow and smoke is given off.
Seed may, however, be considered good if the germinating test gives, say, 70 per cent.
The quantity of seed to be sown on a given area will depend mainly on the quality and particular species.
When sown broadcast, about a pound weight of larch, and full half a pound of Scotch, is allowed per 100 square ft. of seed-bed.
Generally, however, drill sowing is resorted to, and in this case the following may be considered as about an average of the quantity used per 100 square ft.:
Alder 7¾ ozs. Ash 5 ” Austrian Pine 4¼ ” Birch 6½ ” Elm 3½ ” Hornbeam 2¾ ” Larch 7½ ” Maple 5 ” Scotch fir 2¾ ” Silver ” 13 ” Spruce ” 3½ ”
Sometimes a small quantity of guano or other manure is sprinkled over the seeds, after which they are gently pressed down with a light roller, and the soil, which was temporarily deposited along the margin of the bed, replaced by the “cuffing-board” or riddle. When seeds are sown early, and with care, on well-prepared ground, watering is seldom necessary; but still, with small seeds and in very dry ground, an occasional sprinkling the last thing at night is highly beneficial. Great care is, however, necessary to ensure the soil being thoroughly moistened. Protection from mice and birds must be afforded in some such manner as by coating the seeds with red lead; and an occasional shading of the bed in very warm weather might be advocated. There are not a few kinds of seeds, such as those with a hard covering, that it is almost imperative to steep in water before sowing. Larch seed, in particular, can be soaked for a week without fear or harm, and many leguminous seeds for two or three days with great advantage. Some seeds do not come up until the second year, such as the ash, pyrus, thorn, etc., and in these cases it is but a waste of ground to sow them as collected. They should be mixed with sand, as before directed, and stored away for a year before being sown.
It should also be remembered that, as a rule, the sooner seeds are sown after being collected, the stronger will be the young plants.
Soon after germination, hand weeding must be commenced, and this may most successfully be performed after a shower of rain, as the young plants then suffer less from loosening of the soil, consequent on pulling out the weeds, than would be the case in dry and warm weather.
The above method of raising plants from seeds will be found suitable in most cases, but in respect of choice or half-hardy trees the shelter afforded by a frame is usually provided. In this case the seeds are sown in pots or shallow boxes, according to quantity, and placed in an unheated frame.
The best time for seed-sowing is from the first to the fifteenth of April.
Transplanting the young seedlings may be taken in hand usually after the first year, but no hard and fast line can be laid down, so much depending on the season and rate of growth of the young plants. The experienced eye can always tell when seedlings should be lined out. The best time for this operation is after the spring frosts are at an end, for, if planted out in the autumn, the frost is apt to lift the tiny seedlings wholesale from the ground.
After this they should be transplanted at least every second year until planted out permanently.
=By Cuttings.=—Propagating trees and shrubs from cuttings is at once a simple and inexpensive way of getting up a stock of such kinds as may be increased in that way. The best months are August and September, at which time the temperature of the earth and air are equal, and roots are most readily emitted.
Choose a sheltered and partially shady border for the insertion of the cuttings, and be sure that the soil is not stiff and water-logged, but fine, rather inclined to sandy, and moderately dry. It should be well forked over and cleaned of weeds, large stones being also removed.
The cuttings may be made of the present year’s growth, with a small portion—“heel” it is generally termed—of the old wood, and cut clean across beneath where a bud or shoot has protruded. Until a sufficient quantity has been made, they should be stuck loosely in a heap of sand or soil, and in the shade. Cuttings should be taken from the sunny side of a tree or shrub.
In planting the cuttings, stretch a garden line along the previously prepared ground, and, having removed a trench about 6 in. deep, by cutting in a perpendicular manner with a spade along the front of the line, proceed to place the cuttings not too closely together, and leaning somewhat backwards in the trench cut out. This being done, it is always well, so as to hasten the formation of roots, to sprinkle a small quantity of sand or grit along at the base of the cuttings, at the same time regulating these as to their distances apart and upward inclination, the remaining portion of the trench being filled up with the soil formerly removed. Firm tramping is one of the chief points to be observed, as cuttings will not take at all quickly in loose soil. The line should then be moved forwards about 12 in. and the same method of procedure followed until the whole of the cuttings are inserted. For such shrubs as the common and Portugal laurel, privet, box, euonymus, laurestinus, aucuba, etc., the above method will be found the quickest and best for raising young plants from cuttings. It should be stated that cuttings taken from the sunny side of a tree or shrub always root more freely, and turn out a greater number of plants, than such as have been cut from the shady side—indeed, this point should be carefully borne in mind and acted upon. Conifers, such as the various species of Cupressus, Juniperus, the Wellingtonia, etc., are also readily raised from cuttings inserted in the ground out of doors. It is, however, well to put such cuttings in boxes, so that they have the advantage of being placed in an unheated frame, this greatly enhancing the speedy formation of roots. Two or three large frames are always useful in the nursery for the reception of choice cuttings, seeds, etc., and if boxes, say, 24 in. by 14 in. by 5 in., are made just to suit the dimensions of the frames, a great number of young plants, cuttings, and seeds of the less common kinds will find a beneficial protection. The boxes should be made of stout wood, and have six holes bored in the bottom of each, so that the excess water may readily pass away. Before planting these, fill each with a mixture of half sand, half soil, broken finely down, the cuttings being inserted in small holes made by a sharp-pointed stick. A thin coating of sand placed on the surface will greatly facilitate the process of rooting. Cuttings of coniferous trees should have 2 in. of ripened wood attached to them, and be inserted 4 in. deep in the ground; while, for most others, the cuttings may be 8 in. long, 3 in. being inserted in the soil.
=From Layers.=—For increasing game coverts, shrubberies, or some of those trees and shrubs that cannot well and speedily be raised from cuttings or seed, layering will be found a convenient and cheap method. There are several other advantages too, as no protection of any kind is necessary, and the risk of loss is reduced to a minimum. It is, however, generally resorted to as a means of increasing such plants as cannot readily be raised from cuttings, and applies with greatest force to the rhododendrons and azaleas, the magnolias, coniferæ of various kinds, and several species of our hardy deciduous trees.
The operation of layering is very simple, and consists merely in bending down the outer branch of a tree or shrub and bringing it in contact with the soil, it being there held in position by means of a hooked peg. Before fastening the layer with the peg, it is well, however, to remove a portion of the bark from that part of the layer that is to be brought in contact with the ground, this arresting the flow of sap and hastening the formation of roots. The soil beneath the tree or shrub should be first loosened, and, if found hard and stiff, a small quantity of sand and leaf soil might with advantage be added. The same principle is carried out in all kinds of layering, but the position of the plant will alter the method of bending over and bringing in contact with the soil. In the case of layering coniferæ it is not only necessary to bend over and peg down the branch, but, so as to form a leader and assist in gaining an upright position, it should also be tied or staked in a vertical position. Generally speaking, trees and shrubs require two years before the branches that are layered are sufficiently well rooted to be removed from the parent, but a few kinds require nearly double that time before they can be severed with safety. A good plan is, after the second or third year, to cut through the layered branch behind the point that is brought in contact with the ground, and to let it remain in position for another year. It may then, except in a very few cases, be lifted and lined out with others in the nursery border, the object being to get it into a good habit of growth before being finally planted out.
Most varieties of trees and shrubs can readily be increased by layering the side branches in the way above described, and it is a good plan to cover over with a spadeful of earth that part of the branch brought in contact with the ground.
=By Grafting.=—This may best be described as a makeshift method of increasing trees and shrubs. It has only a few advantages, and many disadvantages, as is well known to every one on a large estate who goes in for collections of the less common kinds of trees and shrubs.
If a plant cannot be increased conveniently by any of the above methods grafting may be resorted to, but the work should only be entrusted to those who have great practical knowledge of the art, and who have paid particular attention to the evils attending injudicious grafting. Some of the errors in grafting may be cited as follows: Working on too tall stocks whereby an unnatural appearance and continual source of danger in windy weather are brought about; grafting small scions on large stocks, and grafting evergreen on deciduous species—all of which have tended, in a marked degree, to lower the art in the opinion of horticulturists generally.
The grafting of conifers may be performed at one of two seasons: either early in spring or about the month of August. Two-year-old stock are mostly to be preferred, so that the stock and scion may be of as near a size as possible. Several methods of grafting are adopted, but that generally practised is what is known as “side grafting.” This consists in making a clean cut in the stem, downwards, for about an inch in length. A transverse cut is made at the termination of this first cut, whereby a piece of the bark wood is removed from the side of the stock. The scion is next prepared by being cut off square at the end, and one side of the wood shaved off for about an equal length to the cut on the stock. Place the scion in the notch made on the stock, and be careful that the barks, on one side at least, come neatly together, for on this hangs the whole fate of successful grafting. The scion should, indeed, be made to fit as nearly as possible and replace the wedge cut from the stock. Tie firmly and carefully with bast matting, and cover over with prepared clay or grafting wax. Another method consists in making an incision obliquely in the stock, the scion being so prepared that one side of it forms a sharp edge, in order that it may be readily inserted therein, the bark of the scion and stock coming neatly together. Tie with matting as before directed, and cover over with clay or grafting wax. Inarching, or grafting by approach, consists in bringing the scion into union with the stock without detaching it from its own stem, and the separation is not made until the new connection has been formed.
=Budding.=—This is usually performed in July, and in the case of certain shrubs has been found useful. The bud should, in addition to its strip of bark, have a portion of the cambium attached, as unless this be present to unite with the cambium of the stock the operation will fail.
The bark of the stock is cut into a =T= shape, opened with the end of the budding knife, and the bud slipped neatly in. Bast matting will serve for tying, until a junction takes place, which is usually effected in five or six weeks.