The tying material should be cut and removed within a few days after the
bud starts, to prevent strangulation of the tender shoot. Be sure to
keep native growth of the stock trimmed off until midsummer to force
growth of the bud.
The second period for successful plate budding of the walnut centers
around August first, varying somewhat with the weather conditions. Buds
of the current season's growth are used. The time must be late enough
for these buds to be well matured, and early enough so that the stock is
still growing and the bark slipping. If the buds are immature, or the
bark tight, the operation will be a failure.
The buds remain dormant during the following winter, and are forced into
growth by cutting off the stock above the bud early in the spring. The
tying material, if durable, should be removed about 30 days after
budding.
If conditions are right and the work is properly done, a high percentage
of "takes" may be expected. In summer I preferably place the bud on the
shady side of the stock, or shade it with a little skirt of white paper
tied just above the bud.
Chestnuts can be budded by the same method, but the spring budding
should be done earlier, while the stocks are in bud, and the summer
budding should be done two or three weeks later than with the walnut.
I have not tried the plate bud on hickory or pecan, but it is the only
budding method I use on walnut and chestnut, and I have tried them all.
When it comes to grafting, the simple splice graft, as illustrated, is
very successful, but it should only be used when scion and stock are of
the same size. It works splendidly on chestnut, filbert and hickory, and
can also be used on walnut; however, I prefer the modified cleft graft
for the latter, because of the bleeding problem.
In making the splice graft, the diagonal cut should be about four times
as long as the diameter of the scion, to prevent slippage in tying.
For the modified cleft graft I cut the stock off at the selected point
at an angle of from 45 to 60 degrees. This greatly facilitates the
healing of the entire wound.
The cleft is made not by splitting, but by making a cut with a sharp
knife, beginning at the apex of the stock and cutting diagonally
downward and inward toward the center of the stock.
Before making the cut, the scion should be selected, and the wedge cut,
with one face slightly longer than the other. This enables one to
properly judge the depth and angle of the cleft, thus securing a fit on
all four cambial lines. The longer face goes toward the main body of the
stock, and is left slightly above the top of the stock. The apex of the
stock is squared off slightly before the cleft is cut, and the knife is
set very slightly on the wood at the starting point, rather than between
the bark and the wood. Care at this point guarantees very rapid healing,
with no dead tissues or "heel" on the stock, sometimes called "dieback."
Remember to watch all ties in grafting to prevent strangulation of the
tender new growth. This, with removal of sprouts or suckers from the
stock below the graft are two very important features of after-care, and
neglect can nullify the most expert work in the grafting operation.
In grafting the black walnut I prefer to use the side graft because of
the bleeding problem. This is precisely the same as the modified cleft
graft except that the cleft is made about three-fourths of an inch below
the apex of the stock. By making the graft a little below the top of the
stock one can tie and wax it, without waxing the top of the stock, which
is permitted to bleed at will. This freedom to bleed relieves the
pressure of the sap at the graft, where healing takes place without
flooding.
For stocks under an inch in diameter, I use the splice and modified
cleft grafts exclusively. For larger stocks, such as are encountered in
top working, other methods are preferred.
One can cut the main stock off just above a small limb, and graft one or
more of the limbs. Again, one may cut the large stock off a year in
advance, and bud or graft one or more of the suckers that are thrown
out.
If neither of the above methods are applicable, one can use either the
simple bark graft, or the slot bark graft.
In making the simple bark graft, I cut the stock off at a 45 degree
angle as for the modified cleft graft. The scion is prepared by making
one long wedge face, and on the other side make two short faces so that
the point is triangular.
To insert the scion make a cut through the bark downward from the apex
of the stock. Insert the scion between the bark and the stock, with the
long face next to the wood, and force gently down until just a little of
the face of the wedge shows above the top of the scion. It is well, in
case the stock is large, to place three or four scions around the stock,
removing all but the strongest after a year of two.
This graft is satisfactory for thin-barked species, but for the hickory,
the slot bark graft is preferable.
For this graft, the scion should be trimmed as a wedge, with one face
about twice as long as the other. Two parallel cuts are made through the
bark at the top of the stock a distance apart equal to the width of the
scion wedge. This strip of bark, or "tongue" is loosened at the top, and
the wedge is forced between it and the wood, with the long face next to
the stock, as in the simple bark graft.
Secure tying and waxing should be practiced in all grafting. Small nails
or tacks driven into the top of the stock will help in anchoring the
tying material to the sloping surface.
Inexperienced propagators should get it clearly in mind that union takes
place only in the new growth. This new growth builds up from the cambium
layer, which is the outside layer of wood cells that lies just beneath
and in contact with the bark.
This is why it is so vitally necessary that the lines between the bark
and cambium be placed in parallel contact as closely as possible, in the
splice and cleft grafts. Never mind if the outside of the bark of scion
and do not match perfectly, due to differences in the thickness of the
bark. It is the inside line of the bark that must match.
Actual union takes place along this cambial line. The old wood of the
wedge and cleft cannot, and never does, unite.
A word about scions. I seldom use a scion with more than two buds. The
best scion wood is of the previous season's growth, if it is of good
diameter and well ripened. Thin, slender twigs give poor results. On
old, slow-growing, bearing trees it is sometimes not possible to get
good scion wood one year old. In this case it is best to take some of
the older wood in cutting the scion. When used, the wedge should be cut
from the two-year wood, just below the one-year wood, with the top of
the scion carrying two or three buds on the new wood. The tip of the
scion should be waxed, if cut.
Scions should be cut when perfectly dormant and kept in cold storage
until used. If kept too warm and wet the buds may swell, making the
scions worthless.
It is quite possible to cut the scions about three weeks before the buds
begin to swell and get good results by grafting immediately. The chief
danger from this practice is that late frosts may nip the buds after
starting, which is fatal to the new scion.
Waxing all cut surfaces, including the tip of the scion, should be
practiced except as explained when the side graft is used for walnuts.
Some advocate waxing the entire scion, also. If this is done I think it
better to leave the buds unwaxed.
Have your knife very sharp. A broad blade is desirable in a grafting
knife, as it helps in making smooth, flat surfaces in wedges and clefts.
For budding, use a knife with a narrow blade, but also very sharp.
Develop skill in making the scion wedge, and in cutting the cleft just
the right depth and width for the scion selected. Experiment on
worthless material until you get the knack. If you are a good,
natural-born whittler you will find it a greater asset than a college
degree.