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.