The Yale expositor., 1916-04-27

Grated Into the Trunk Of the OIL
prepared by the United States Depart
ment Of Agriculture)
Bridge grating, the use of scions or
small limbs to connect the calnbium
above and below a large wound or cir
died strip, may be practiced success
fully on almost any kind Of fruit tree
that can be propagated readily by
grating. 1t is used more often with
the apple than any other fruit, but
pear trees often are treated In this
way, especially in certain sections.
There seems to be no reason why the
method should not also be successful
on plums and cherries. according to
Farmers Bulletin 40, Bridge Graft
ing OF Fruit Trees" just issued by the
department. Peaches, however. graft
less readily and there may be some
question as to the usefulness of the
method IN the case OF this fruit. While
seldom used on shade OF other orna-
mental trees, the author, w. F.
Fletcher, writes that this method of
grating probably would prove success
full in overcoming certain types of in
juries to them.
Mechanical injuries which may be
remedied are usually inflicted by ami
mails, by burrowing insects, or by i'm
plements carelessly used. Various
diseases, such as pear blight, alAo
cause local injuries which may call for
bridge grating. The trunks of pear
trees are not infrequently completely
girdled and killed by pear blight.
Bridge grating, II done in time, how
ever, may save the tree.
The method also is useful when
large areas of bark have been killed by
sun scald or other troubles. The au-
thor Of the bulletin points out, how
ever, that protection Of trees against
rabbits and mice and disease is, OF
course, better than having to bridge
craft to overcome damage.
Methods Of Bridge Grating.
To be effective, bridge grating
should be done in the spring before
growth starts, though sometimes 1t can
be done after growth starts II dormant
scions for the purpose can be secured.
Prepare the wound in the tree by
cutting away all dead tissue and thor
oughly cleansing the injured parts. If
possible, sterilize by washing with a
solution of bichloride of mercury, cop
per sulphate, or some other antiseptic.
The irregular edges of the bark above
the girdled tract or wound should be
cut back into an even edge, far enough
from the wound to make certain that
healthy cambium is under the bark.
For the grating, select scions from
wood Of the previous seasons growth,
either branches which grew the pre-
ceding season or water sprouts that
are only a year old. The scions should
be little longer than the space which
is to BIO bridged, so they will arch
slightly over the central part Of the
wound.
Bowel the scions at each end on the
same side Of the scion with a long
sloping cut so that the wedge-shaped
ends thus formed will be relatively
thin and permit their being thrust
we'll under the bark without danger Of
separating It unduly from the cambium
at the points of insertion. The plac-
ing of the scions will be facilitated
IL the bark at the margins of the
wound is slit for a short distance at
the points where the ends are to be
! inserted.
Importance Of Uniting camblum.
In placing the scions It is Of the
greatest importance that the cambium
of the scions which is exposed in the
sloping cuts at the ends be brought
into intimate contact with the cam
blum that lies under the bark at the
margins of the wounded area. The
union OF scion and tree can occur only
where the cambium layers Of the two
come together. The scions may be Sc
cured in their proper positions, II need
be, by driving a small nail through
each end into the trunk. This will aid
in drawing the cambium OF scion and
trunk closely together.
The operation is completed by thor
oughly covering the area occupied by
the ends of the soions and the mar
gins of the wound with grating wax,
strips OF waxed cloth, or by some
other means that adequately will pre-
vcsi these parts from drying out