to March 1st, the seedling trees are cut back to stubs, the ends of
which may be from one to three inches in diameter. Wounds larger than
this size take years to heal and endanger the life of the tree. Large
trees can be operated on as well as small seedlings, only one has to go
higher up so as not to cut too large limbs. Figure 1 shows a seedling
pecan tree 18 inches in diameter, which was stubbed back in the winter
of 1911-1912 and successfully budded the following summer. The result of
this drastic heading-back is a numerous growth of vigorous, rapidly
growing shoots near the ends of the stubs, by which Nature endeavors to
heal over the wounds. The cambium in these vigorous, sappy shoots is in
the most active condition possible; just the condition most suitable for
the union of stock and scion. This optimum condition cannot be secured
except by the forced growth as the result of the heading back. Our
experiments, year after year, have shown that on the ordinary new
shoots, even on active young seedling trees, the percentage of
living buds was much less than on the forced shoots of the headed-back
trees.
[Illustration: Fig. 1. Seedling pecan tree, 18 inches in diameter, cut
back in winter, showing summer's growth of vigorous shoots ready for
budding.]
[Illustration: Fig. 2. First operation. Making parallel cuts on stock.]
[Illustration: Fig. 3. Second operation. Making vertical cut between
parallel cuts on stock.]
[Illustration: Fig. 4. Third operation. Loosening bark on stock.]
[Illustration: Fig. 5. Fourth operation. Making parallel cuts on bud
stick.]
[Illustration: Fig. 6. Fifth operation. Making vertical cut between
parallel cuts on bud stick.]
[Illustration: Fig. 7. Sixth operation. Taking bud from bud stick.]
[Illustration: Fig. 8. Seventh operation. Fitting bud to stick.]
[Illustration: Fig. 9. Eighth operation. Beginning the tie.]
[Illustration: Fig. 10. Ninth operation. Finishing the tie.]
[Illustration: Fig. 11. The tie complete.]
[Illustration: Fig. 12. Bud united.]
[Illustration: Fig. 13. Bud stick of present season's growth. The three
lower, or basal, buds are best.]
[Illustration: Fig. 14. Bud sticks of previous season's growth.]
The different steps in the operation of patch budding are briefly as
follows:
1st operation. Making parallel cuts on stock. See Figure 2.
2d operation. Making vertical cut to remove bark from stock. See Figure
3.
3d operation. Loosening patch on stock. See Figure 4.
4th operation. Making parallel cuts on bud stick. See Figure 5.
5th operation. Making vertical cut to remove bud patch from bud stick.
See Figure 6.
6th operation. Taking bud off bud stick. See Figure 7.
7th operation. Inserting bud on stock. See Figure 8.
8th operation. Beginning the tie. See Figure 9.
9th operation. Wrapping the bud. See Figure 10.
10th operation. The completed operation. See Figure 11.
Figure 12. Bud united.
These illustrations should make the method self-explanatory.
_Knives for Patch-budding._
Two sorts of knives are used for patch-budding, the double one for
making the parallel cuts and the ordinary budding knife for removing the
patch.
_Cambium._
Professor Bailey, in his "Encyclopedia of Horticulture," says, "The ways
and fashions of grafting are legion. There are as many ways as there are
ways of whittling. The operator may fashion the union of stock and scion
to suit himself if only he apply cambium to cambium, make a close joint
and properly protect the work."
The fundamental basis of the whole science of grafting is cambium. What
then is this important substance by means of which one plant may be made
to live and grow and produce on the roots of another? If we strip off
the bark of any actively growing, woody plant we will find just beneath
a soft, colorless substance; this substance is cambium. It feels slimy
to the touch and if scraped with the finger nail a little doughy mass
can be raised. As we examine it it will be seen to quickly darken to
cream color, then to yellow and finally to dark brown. A change has
taken place in it in a few seconds, right under our eyes. When we first
exposed it, it was living, active and capable of building the most
complicated of plant structures; now it is dead, inert and impotent. If
we examine the smallest portion of this doughy mass under a compound
microscope we will find it not merely slime but a highly organized
tissue made up of countless minute cells, each with a delicate wall
about it and containing a thickish liquid (protoplasm). The cambium
cells are brick-shaped, and are placed end to end, with layer
overlapping layer, like bricks in the wall of a building. The
microscopic structure of cambium tissue gives us a clearer conception of
its extreme delicacy. It is one of the most sensitive and delicate
substances in all nature. Exposure to the air will kill it and
completely destroy its functions in a few seconds. It is easily crushed
by slight pressure and quickly killed by exposure to drying, frost,
moisture and sunlight. Nature shows her extreme care of it for in making
bark she has formed for the delicate cambium a perfect protective
covering. Like the cambium the bark is composed of cells, as in fact are
all animal and vegetable structures. But the cells of the bark have
thick walls of a tough, corky substance, and each cell contains air
instead of protoplasm. The corkiness of the bark makes it an impervious,
waterproof covering that does not allow the cambium to be dried out or
to be washed by external moisture. The air in the bark cells being in a
still condition is a non-conductor of heat, and layer of bark
overlapping layer, the cambium is completely covered with a dead-air
blanket. This keeps it from being frozen in winter and from being
overheated in summer, just as a dead-air space in the walls of a
building protects from extremes of heat and cold. From this it is plain
that nature takes great pains to cover and protect the delicate cambium
from all external influences. This stands in striking contrast to the
careless manner in which many propagators and planters handle the
delicate parts of trees. It also explains why some budders get such a
small percentage of living buds and some planters so few living trees.
Cambium is the building material of plants and without it growth is
impossible. It covers every portion of the tree from the topmost
terminal bud to the deepest root tip like a living blanket. During the
growing season the cambium cells divide lengthwise forming new cells.
These divide again and grow, and new cells are formed, until by fall a
complete mantle of bark covers the outer surface of the cambium, while
within it has built up a solid layer of the woody structure of the tree.
A few rows of cambium cells are left in an embryonic condition to carry
on growth the following year. The cambium is thus the only tissue of the
tree that retains from year to year the power of active growth. The
layers of wood and bark, after performing their functions for a few
seasons, gradually die and are overlapped by new layers, but the
cambium remains living throughout the entire life of the tree even if it
be, as in the giant Redwoods, thousands of years.
Besides forming the regular wood of the tree the cambium also grows out
over cut places and builds in woody tissues that heal over the wounds.
It is owing to this fact alone that budding and grafting are possible.
The callus on cuttings and root grafts is another evidence of the same
phenomenon, for the cambium of the roots of a tree is continuous and
identical with that of the branches.
_The Stock._
The whole practice of successful grafting and budding is the proper
handling of active cambium. The cambium is the cementing material that
unites stock and scion and unless there is active cambium there will be
no union. It must be said here that no matter how great the future
growth of the union, the scion never becomes truly united or fused with
the stock. The cambium grows all over and around the cut parts and
cements them together, but if the graft union be split open fifty years
later, the dead wood of the original scion may be found of the original
size and in the original position. Since, then, successful grafting
depends on the union of the cambium of the stock with that of the scion,
theoretically the best time for grafting and budding would be when the
cambium is most active. Actual nursery practice shows that this is
practically correct, at least as regards the stock.
The ideal stock for propagation purposes is the young seedling of one or
two years growth. In such a stock all the tissues are new and fresh and
working to their maximum capacity and the cambium is in its most active
condition. In top-working old trees it will be found that though the
branches may appear vigorous, they are a long way from having anything
like the active circulation found in small seedlings. Buds put in these
branches would give a very small "live," while the same care on nursery
seedlings could be counted on giving a high percentage of living buds.
In top-working, therefore, it is found necessary in order to get the
cambium sufficiently active, to stub back the branches to mere pollards.
This cutting back should be done in the winter or dormant season. The
following growing season will see a dense growth of very vigorous shoots
trying to repair the injury. See Figure 1. These shoots are ideal stocks
for, on account of their having all the sap from the greater root of the
mature tree, the cambium will be even more active than in the nursery
seedling. Often when nursery seedlings are in partially dormant
condition, owing to unfavorable weather or other conditions, they may be
forced into budding condition by slashing off part of the growth above
where the buds are to be inserted. In our top-working experiments this
fact was further emphasized by a windstorm which broke off many of the
sappy shoots just above where the bud was put on. Every single one of
these buds "took," though some others, just as carefully put on, failed.
The success of all the buds on the wind-broken shoots was undoubtedly
due to the forcing of the cambium growth just at the point where the bud
was inserted.
_The Scion._
Although it is desirable to have the cambium of the stock in an active
growing condition, it is quite the reverse with the scion. The reason of
this is evident, for if the scion were active, it would soon exhaust its
small supply of food and die before the union could be formed and it
could get its permanent supply of nourishment from the root. It is
desirable to have scions fresh and firm but in a quiescent condition
until pushed into activity by the growth of the stock. If, on the other
hand, the scions or buds become too dry the sap will not be able to
revive them and no union will be made.
For patch-budding, the buds may be cut from scions or bud sticks of the
present or the past season's growth. Figure 13 shows a bud stick of the
present season's growth from which the leaves have been cut. Such a bud
stick cannot be obtained until July, for before that time the bark is so
tender that it is impossible to get the bud patch off the stick without
crushing it or peeling off the cuticle of the bark. The basal buds of
the present season's growth, Figure 13, make the best buds because they
are more mature and dormant than the buds above them and as they have
shed the leaf stalk they can be tied in more easily and snugly than
those with the thick, fleshy base of the leaf stalk attached. Some
budders make a practice of cutting off the leaves ten days or two weeks
before they commence budding and leaving the scions on the trees to
ripen the buds and shed off the bases of the petioles. There is in this
way no danger of the thick fleshy leaf base decaying under the wrap and
souring and killing the buds.
Figure 14 shows budwood of the previous season's growth. This budwood
can be cut during the winter and kept over in fresh dormant condition by
being packed in damp sawdust and carried over in ordinary cold storage
or in a refrigerator. It will be ready for use in the spring as soon as
the bark will slip on the stocks. By this method the budding season may
be greatly extended and propagation started at least two months before
any of the present season's buds will be sufficiently mature for use.
_The Kinds of Buds to Select._
As to the buds themselves the most desirable are those at the base of
the season's growth. See Figure 13. These, though not large, are plump
and fully mature. The bark is smoother and firmer about them than higher
up the stem and there is no leaf stalk to interfere with cutting them
accurately and making a close fit and tie. These buds are dormant and
there is little danger of their pushing into growth in the fall and
being cold hurt the following winter. For best success in patch budding
it is not desirable to select very large, overdeveloped buds, or those
that have grown so rapidly as to stand out on a little pedicel or basal
stalk. In removing such a bud from the stick, the central column of the
pedicel will often pull out and remain on the stick. Such a bud will
almost invariably die. An observation of pecan buds in general will show
that they are normally triple in form, the largest above and two smaller
ones beneath it. The largest bud will grow first but if anything happens
to it, the next one will take its place.
_Tying in the Buds._
A good deal of the success in patch-budding depends on the tying in of
the buds. The cambium must be thoroughly protected if a union is to
result. It is necessary to have some kind of tie that will retain the
sap as well as exclude external moisture. After experimenting with
different materials and methods I have finally abandoned all except the
waxed strip tie. This is made by dipping sheet cotton in pure, liquid
beeswax and pressing out all extra wax. The cloth after dipping is
formed into convenient sized rolls. From these rolls the cloth is torn
at budding time into strips a quarter of an inch wide and from six to
eight inches long.
In tying in a bud hold it firmly so that it will not slip and begin at
the top and bind it in very tightly with the waxed strip. Reverse the
tie at the rear of the bud like a surgeon's bandage and cover the patch
completely, leaving only the tip of the bud sticking out. The wax in the
cloth will cause the tie to adhere sufficiently to the wood so that no
other ligature is required. In budding in the spring, when the flow of
sap is very copious, it is well to tie in a small splinter about the
size of a match just below the bud to drain off the excess sap. This
will save many buds from being killed by souring of the sap. In two to
three weeks time the tie should be loosened so that the rapid growth of
the stock will not cause the tie to cut into the bark.
_The Mechanics of Patch-budding._
After all has been said about cambium and stocks and scions and their
relation to each other, there is still volumes to be written on the
mechanics of pecan propagation. I do not want to scare anyone off from
trying, but if there is any plant more difficult to propagate than the
pecan, I have not yet found it. Even experienced propagators of general
nursery stock have given up pecan budding as a bad job. On the other
hand, a novice or "pecan crank" who is handy with tools and has the
patience to study out the causes of his failures, may acquire the skill
to obtain almost a perfect "live" of buds. This all goes to show that
extreme precision is the password in the mechanics of patch-budding. In
the first place, the knives should be of the finest quality so that they
will hold a clean, fine edge. All cuts should be made with accuracy and
precision, so that there are no rough edges and bias corners. The number
of living buds will, under ordinary circumstances, be in exact
proportion to the accuracy with which the bud patch fits the place made
for it on the stock. The experienced pecan budder as he takes the bud
off the stick can tell whether or not they will grow. If he tears the
bark in cutting the patch, he drops that bud and cuts another; if the
bud patch splits, he discards it; if his fingers touch the cambium or
the bud patch falls to the ground, he wastes no time with it, but cuts
another and another until he gets the conditions perfect. There is
little use in tying in any bud that does not fit perfectly. For this
reason it is desirable to have the bud stick of the same diameter as the
stock. The bud patches from thin or small scions have to be stretched to
fit and generally give a poor "live"; likewise, the buds from the more
or less ridged portion at the top of the bud stick. The transfer of the
bud patch should also be made quickly so that the cambium will have the
shortest possible exposure to the air.
_After Treatment._
The process of patch-budding is not complete even after a good "live" of
buds is secured. It still requires some judicious after-treatment to get
them into good normal growth. On account of the drastic heading back the
tree has received, practically every dormant bud will be forced into
active growth. These will push out so vigorously in spring that if not
held in check, they may completely overgrow and crowd out the buds put
in. Attention should be given during the early growing period to see
that the buds put in have sufficient room for proper development. If all
or too many of the seedling buds are rubbed off, the inserted buds will
not be able to carry all of the heavy flow of sap and so may be drowned
and killed. On the other hand, the inserted buds may not start unless
forced by the extra sap obtained by rubbing off a portion of the
seedling buds. A good deal of horticultural judgment is required to
adjust the proper balance between the seedling and the inserted buds so
as to get the best development of the latter. When the inserted buds are
able to carry all the sap of the tree, all seedling shoots should be cut
out and attention directed towards forming the new growth into a strong
symmetrical top.
If conditions are favorable, there will generally be some nuts the
second season. By the third year the transformation from the seedling to
the named variety should be complete, and a good crop of high class nuts
should be expected.
* * * * *
MR. POMEROY: Would it not be an advantage if two persons worked at the
budding? After the cuts are made, one could be taking the part from the
stock and the other taking the bud from the budding stick.
THE CHAIRMAN: That is a very good plan. One man could put in the buds
and another man could tie--a boy handy with his fingers in making ties.
PROFESSOR SMITH: Why the superiority of beeswax to grafting wax?
THE CHAIRMAN: A good many budders object to grafting wax, on account of
the oil therein contained being injurious to the trees. A great many
people have dead trees as a result. Trees don't like oil, and for that
reason we use beeswax and only the purest kind of beeswax. In fact,
these pecan cranks who want to do things as they should be, like to
examine the wax to see if there is pollen or bee bread or anything
foreign in it.
PROFESSOR SMITH: Is there any particular time that is best for grafting?
PRESIDENT HUTT: Yes; in the early part of the season there is a very
vigorous flow of sap and we find we lose more buds then than in the
later grafting. In early grafting we put in drainage, just like the
physicians, little tubes or something to drain out the moisture. We put
in a little chip and tie over it very carefully so if there is any
drainage it may escape. In the fall and late summer drainage is not
necessary at all, and we really get better unions then when the trees
are slowing down than we do in the spring when they are full of sap.
MR. STORRS: In selecting your buds, do you take them from trees that
have borne, or from young trees, or indiscriminately?
PRESIDENT HUTT: We take them either from bearing or young trees. It is
not important which, just so you get the right kind.
The important thing is to select good fresh active stuff, and
particularly good sized scions and not small ones.
In budding we fit one side perfectly, and on the other side we leave a
space of one sixteenth of an inch like a door. We didn't do that at
first and we lost a good many buds because the active growth began on
both sides. We had to leave a place there at the side, an expansion
joint, to take care of that.
MR. STORRS: Then you fit them at the top and bottom and at one side?
THE CHAIRMAN: Yes, that's it.
THE SECRETARY: This is one of the most important papers ever read before
this Association, and that is because the success of nut growing
anywhere is absolutely conditioned on our knowledge of propagation. If
the propagation of nut trees were as easy as the propagation of apple
and peach trees, we would probably now have in the north as many
orchards of good nut trees as of apple and peach trees. Any one who has
tried this budding of nut trees will, I am sure, appreciate the
difficulties that Professor Hutt has described and the pains he has
taken in telling us about them. This is the beginning of the
demonstrations in propagating. They will be continued tomorrow; we will
have then three or four of the most expert grafters and budders in the
country, perhaps, who will give further demonstrations.
I would like to ask Professor Hutt a question. I noticed that in putting
in some Persian walnut buds this summer, all died except a couple where
the tops accidentally broke off.
THE CHAIRMAN: That is explained by the illustration I gave of the wind
blowing off all the shoots. Every one that was blown off lived even
though some were badly torn. It was simply forcing the cambium at that
point where it was needed. Mr. Roper had an experience of that kind.
[Illustration: W. N. ROPER
Vice-President Northern Nut Growers Association]
MR. ROPER: We put buds on stock that was not very active, so the trees
were cut back to six inches above the bud, forcing all the growth
into the bud, and I suppose 95 per cent of those buds lived; on the
trees not cut back the buds did not live.
THE SECRETARY: You have spoken about soaking the scions in cold water;
does not that injure the buds? We have been told heretofore that keeping
the scions in water started the cells into activity and rendered them
less likely to grow; but perhaps that referred particularly to scions
for grafting rather than budding.
THE CHAIRMAN: I would like to ask Mr. Wiggins that question, he is a
specialist.
MR. WIGGINS: One of the dangers in keeping bud wood is that of keeping
it in too much moisture. It does not require much to keep the bud plump.
THE SECRETARY: I understand the reason for soaking is simply to allow
the bud to be taken off.
THE CHAIRMAN: Yes.
MR. JONES: In our experience the soaking of wood does not injure it for
budding, but it does for grafting. You can soak the wood for budding all
you want to, we have soaked it until the top bud came out.
THE SECRETARY: I am interested in knowing about this special wax cloth.
Can it be used also in grafting?
THE CHAIRMAN: The other is much cheaper for that purpose. To just cover
the thing up and exclude the air is all that is necessary in grafting.
Liquid wax--four of rosin, four of tallow and two of beeswax--gives
excellent results, but for budding purposes it is absolutely essential
to have good clean wax, and for our purposes we have never found
anything but pure beeswax would answer.
THE SECRETARY: There is a substance called "white wax" which pharmacists
use in making toilet preparations--purified beeswax. It is pure white.
Is that any advantage?
THE CHAIRMAN: I would not use it. It contains some paraffine.
THE SECRETARY: It should consist of purified and bleached beeswax only.
It is more expensive than the ordinary beeswax.
[Read by title.]
UNUSUAL METHODS OF PROPAGATING NUT TREES
DR. ROBERT T. MORRIS, NEW YORK CITY