the mouth of Green River in Kentucky are nearly two hundred acres of
wild pecan trees. So far as we know there are only two trees in that
orchard worthy of propagation. Of thousands of trees there we have
propagated only two varieties. These trees are now too large to top
work, but had it been possible 150 years ago to go in there and select
the desirable nuts, and topwork all the other trees with these, there
could have been a great orchard there now of the highest quality nuts.

Topworking consists in cutting off the top of some undesirable seedling
and replacing it with scions or buds from some desirable variety. It is
just the same as any other grafting or budding process. Almost any size
tree can be topworked but, of course, the larger the tree the more
difficult the operation. A young tree, from two to five inches in
diameter, can be sawed off four or five feet above the ground and
topworked by grafting from two to four scions on it, by the slip bark
process. If the tree is larger than five inches in diameter, it is
better to go up to the first branches, saw off part of them and proceed
just as if each branch were itself a small tree. If the tree is a large
tree, with a number of branches or prongs, it is best to work part of
them one year and leave the remaining branches to maintain the root
system. It would probably kill a large tree to cut the whole top off at
one time. I have seen trees, two feet in diameter, successfully
topworked. It sometimes happens that the scions placed in the tree, in
the spring, for some reason or other, do not grow. The tree then sends
up nice green shoots that later in the season can be budded into just as
if they were small seedlings. The wild black walnut trees, growing
around the fields and hills, can all be very easily topworked to the
English walnut by the slip bark method. The scions must be dormant and
the tree starting into active growth.