This originated as a 1930 selection made by the late Dr. G. A.
Zimmerman, Linglestown, Penna. Very few sound nuts of Zimmerman have
ever been produced, for soon after the first crop the identity of the
tree became lost and eventually it was destroyed together with others in
an overgrown nursery row where it stood. In one known case where there
are grafted trees of bearing age, the nuts are regularly destroyed by
weevils. Such nuts as have been seen by the writer have been of a dull
brown color and have had surface down only about the apex.

The Zimmerman was first catalogued in 1938-39 by Dr. Smith. It is
probable that as many trees of this variety have been sold and planted
as of any one variety but performance records are difficult to obtain.

Potential Varieties

Other varietal selection are being made, mainly by the Bureau of Plant
Industry, Soils, and Agricultural Engineering from trees at its various
field stations. Some of these are already under test as grafted stock in
various parts of the country. The most promising will be released to
commercial nurserymen as soon as their superiority over existing
varieties is established.

Pollination

There is much evidence that chestnut pollen is largely carried by
insects although this has not been fully established. The Chinese
chestnut is largely, although apparently not wholly, self sterile; more
than a single seedling or grafted variety should be included in any
planting. Several seedlings or several varieties would be better. In
seedling plantings, all trees that produce inferior nuts should be
removed in order to avoid danger of undesirable pollen influence,
either on nut characters, or on the genetic makeup of the embryos if the
nuts are to be used as seed.

Harvesting and Curing

Chestnuts should be harvested daily as soon as some begin to ripen and
drop to the ground. They should be placed at once on shelves or in
curing containers with wooden or metal bottoms through which the larvae
of any weevils with which the nuts may be infested cannot penetrate and
reach the ground. In areas of infestation, these grubs soon begin to
bore their way out of the nuts and leave conspicuous holes in the
shells. All infested nuts should be promptly burned.

In order to cure chestnuts to best advantage, they should be spread
thinly on floors, or on shelves, or in shallow containers as just
described, and held in a well-ventilated room. They should be stirred
fre