A number of
considerations must be addressed before attempting grafting; the
grafting (scion) wood, the rootstock and the grafting method.
The scion wood
must be collected while it is fully dormant. Mid March is a good
time. The scion branches should contain buds from the previous seasons
growth. With the walnut family, the buds to be used should resemble
miniature cabbages. Those that resemble closed pine cones are male
flower buds and will not produce new growth. The branches collected
should be healthy, round wood with a small pith (centre of the stem
is hollow in walnut family). The buds closest to the second year
wood are the most mature and usually the best. Wax the ends by dipping
them in melted candle or paraffin wax, wrap the sticks in a slightly
moist towel and store in a sealed plastic bag in a refrigerator.
It must be kept dormant until spring when the rootstock is ready
for grafting and weather conditions are right.
must be a related species to the scion used in the grafting. Black
walnut is a common wild tree in Southern Ontario and makes a suitable
rootstock for all of the Juglans species. This includes heartnut,
butternut and Persian walnut. Same species rootstocks can also be
used. Turkish tree hazel is a good rootstock for all of the hazels,
mainly because it is non suckering. Chestnut is one of the easiest
to graft of the nut tree species but also one of the most difficult
to match for compatibility. American chestnut and Chinese chestnut
are the same type and will inter-graft fairly easily, while European
and Japanese chestnut will often fail when grafted to Chinese or
American. The best success occurs when the rootstocks are the seedlings
of the scion tree being grafted.
When the rootstock
is beginning to burst buds, about 10-15 of May, it is time to start
grafting. Trees can be top-worked, 2 to 3 metres up. Walnut trees
graft better when it is done higher. Walnuts tend to "bleed"
sap in the late winter and well into spring. This bleeding will
prevent any grafting success. To stop this bleeding, it is best
to cut the tree off 5 cm or more above the point where the grafts
will be placed. Do this a week to ten days before attempting the
graft. The shock of losing the top slows the development in the
tree down and the bleeding stops. Cut the stock off again a few
centimetres lower and watch for sap oozing out. If it has stopped,
you may begin grafting. This process is not necessary with hickory
or pecan because the sap pressure is much less. However, the graft
should be made high enough in the tree that sap flow is avoided.
Chestnuts and hazelnuts seldom bleed ,so they can be cut off and
There are a
number of grafting and budding techniques that work with nut trees.
The one graft that works well with all nut trees is the inlay bark
graft and that is the technique that will be described here.
- The stock
should be at least double the thickness of the scion for this
method to work. The stock is prepared by cutting the branch to
be grafted off squarely.
- Make a vertical
cut about 5 cm (2 inches) long, ending at the surface of your
first cut, through the bark until resistance is felt at the sapwood.
- Prepare you
scion which can be 10-15 cm (4-6 inches) long, by deeply cutting
away the wood on one side of the scion about 6 cm or 2½
inches from the bottom end of the scion stick. Turn over the stick
and lightly shave the bark away on the backside of the previous
cut. Finally make a chisel cut on the tip of the scion. Make sure
you have 2-3 good shoot buds on the scion.
- From the
cut surface of the stock, gently lift the bark one side on the
vertical cut made earlier. Slip the flat cut surface of the scion
under this lifted bark, sliding it vertically between the bark
and the sapwood, flat surface facing inward.
- Hammer 2
nails ½ to inches long through the bark, scion and sap
wood to hold the scion firmly in place. A third nail may be needed
to close the gap in the bark beside the scion.
- Cover all
cut surfaces with a grafting wax. If this is not available, seal
the top of the scion with carpenter's glue and cover all cut surfaces
including the scion with aluminum foil. Leave a small flap as
an opening for the buds to shoot out. Cover all of this with a
clear plastic bag and close with a twist tie.
Firmly tie a stick or small branch, higher and beside, the graft
as a perch for birds, so they don't use the scion as a perch and
destroy the graft.
Follow up -
As the graft begins to grow and green shows through the aluminum
flap, cut an opening in the top of the plastic bag to allow the
new growth room to expand. When the graft is well grown, you may
remove the plastic bag and finally the aluminum. As soon as the
graft is a foot or more out, support it with a brace tied to the
branch or trunk.