At the very beginning of these investigations in growing Asiatic
chestnuts as timber trees, it was believed that greater success in
establishment could be obtained by planting seedlings, rather than by
direct seeding. In direct seeding trials during the early thirties the
planted nuts were promptly devoured by rodents. Sixteen years of field
experience has proven the soundness of this belief. The imported nuts
were planted in the Division's nursery at Glenn Dale, Md., and the
resulting seedlings distributed as 1- and 2-year-old trees to
cooperators throughout the eastern United States.
In order to thoroughly test the possibilities of direct seeding as an
economical method of establishment, this Division during seven years
(1939 to 1942, and 1944 to 1946) planted over 7,000 nuts by direct
seeding in 200 locations in 18 eastern States. It was suspected that the
greatest hazard to direct seeding in or near forests would be rodents.
Accordingly, in the spring of 1939 and 1940, 400 nuts and 600 nuts,
respectively, were coated with a strychnine-alkaloid rodent repellent,
and a comparable number of seeds, for both years, were left untreated to
serve as checks. The checks were held in sphagnum moss at Beltsville,
Md., and the nuts to be treated were packed in sphagnum moss and
expressed to Denver for treatment by the Division of Wildlife Research,
the Fish and Wildlife Service, Department of the Interior. Only 5.9 and
2.5 per cent of the treated seeds developed into seedlings, whereas 22.6
and 13.5 per cent of the untreated seeds produced seedlings. Not only
did more of the treated seeds fail to germinate than of the untreated
seeds, but the seedlings from the treated nuts were less vigorous.
Because of the results obtained, the rodent-repellent study was
discontinued at the end of the second year.
In 1941 and 1942, over 4,000 untreated chestnut seeds, representing 22
strains, were planted in 12 locations in eight eastern States. The seed
source was entirely from American-grown, Asiatic chestnut trees growing
in 28 locations in 16 eastern States. They represented Chinese,
Japanese, hybrids, and also a limited quantity of American chestnut
seed. Seed of the American species was included primarily to determine
whether or not it differs from the Asiatic species with reference to
establishment by direct seeding. The results for the two years confirmed
our earlier beliefs: Only 2.2 per cent in 1941, and 4.0 per cent in
1942, developed into seedlings, of which only a remnant have survived.
No species or strain differences were apparent.
"Tin Can" Method
In 1944, the tin-can method was employed in planting 400 nuts in four
eastern States. By this method 15.5 per cent of the planted nuts
developed into seedlings, representing a fourfold increase over results
obtained for the three previous years. One end of a No. 2 can is
removed, and a cross is cut in the other end with a heavy-bladed knife.
The open end of the can is then forced into the ground, over the planted
nut, so that the top lies flush with the ground level. The four corners
at the center of the cut top then are turned slightly upward, to allow a
small opening through which the hypocotyl of the developing seedling can
emerge. The can completely disintegrates by rusting within two or three
years, and does not interfere with the seedling's development.
An examination made of the various burrows about the tin cans, and also
of the teeth marks on fragments of chestnut seedcoats lying about,
indicated that not only squirrels, but other rodents, such as chipmunks,
field mice, moles, and even woodchucks were probably involved in the
direct seeding failures.
In 1945 and 1946, the tin-can method was tested widely on farms, to
determine its possibilities in securing establishment of
blight-resistant chestnuts without a great outlay of cash to farmers. In
1945, five seeds were distributed to each of 90 cooperators residing in
the Piedmont and southern Appalachian regions, and in the lower
Mississippi and Ohio River valleys; and in 1946, to 38 cooperators
residing in the Middle Atlantic States. Preliminary results indicate
that 40.0 and 37.2 per cent of the nuts planted by the farmers developed
into seedlings. It should be pointed out that these results are not
strictly comparable with those of previous years, because most of the
farmers preferred to plant the chestnuts in their gardens, and under
these conditions the nuts were not exposed to the severe competition and
the extreme rodent hazards that occur in the forests.
Further proof of the superiority of planting seedling stock over direct
seeding as a method of establishment is indicated in the results of an
experiment initiated in 1939. One hundred and fifty 1-year-old seedlings
and 150 nuts, all of the same Chinese strain, were planted on cleared
forest lands in the Coastal Plains, the Piedmont, and the southern
Appalachian regions, and in the Middle West. At the end of the eighth
year, at each location, establishment and development of those
originating from the 1-year-old transplants were better than those
originating from seed, and their average survival was six times greater.