chestnut (Castanea dentata) was one of the largest growing
forest trees in eastern North America. It was important for timber
as well as nuts for human use as well as wildlife. A deadly fungus
disease, introduced from the Orient effectively wiped out this chestnut
in the first half of the 20th century.
currently being made at Meadowview in Virginia by the American Chestnut
Foundation to "bring the American chestnut back" as a
forest tree again through a back cross technique using a highly
fungus resistant Chinese chestnut as a source of resistance genes.
After the first cross with an American chestnut is made, the progeny
are screened to recover the trees that have the resistance genes.
These trees are then back crossed to another American chestnut and
the offspring are screened again. This process is repeated several
times to "wash out" most of the Chinese chestnut genes,
leaving a nearly pure American chestnut with the fungus resistance
genes in place. When two of these trees with the resistance genes
are subsequently crossed with each other, 100% of the offspring
will inherit the resistance genes and the trees can be reintroduced
to the forests. The Chinese chestnut cannot be used as a reforestation
tree simply because it does not reach the height of the American
native and would never be able to dominate the forest. It is hoped
that this backcross tree will have the height requirement necessary.
This long term project is past the half way point, with a few years
to go in its program.
A second effort
to bring back the American chestnut at Syracuse University in NY
involves a genetic engineering technique. Pure American chestnut
trees are grown in tissue culture and "hit" with a packet
of genes that will provide a very high level of fungal resistance
to the trees. This project has broken new ground in a number of
research areas. Success is expected in a few years.
maturing and dropping
mollissima), Japanese (C. crenata) and the less resistant
European chestnut (C. sativa) trees have since been introduced
into Canada and the United States to take the place of the orchard
type American chestnut trees. They were only partially successful
as they often lacked the hardiness of the American cousin. As time
went by, and hybrids were developed with American and European trees,
good orchard trees were developed with a fairly high degree
of resistance to the blight fungus. These complex hybrids are the
trees that are currently being used by growers in Ontario.
of West Bank, BC developed a number of largely Chinese chestnut
selections. These were introduced to Ontario. One cultivar, Layeroka,
stood out as an outstanding breeder tree. Layeroka has been superceded
by a number of selections from its offspring as well as others.
Many orchards have been planted using these seedlings and grafted
of grafted trees are suited to the mild areas of zone 6 and 7 (close
to Lakes Erie and Ontario) in Southwestern Ontario and the Niagara
Peninsula. They are best grown on well drained sandy and light clay
loams with a pH of 5 to 6. Generally, the peach soils are well suited
to commercial chestnut orcharding. Irrigation is important in August
and September to help in the sizing and filling of the nuts.
Most Desirable Chestnut Characteristics
- Nut Size
Large size nuts (diameter greater than 1.1 inches) are sold for
a premium. Seedling trees or cultivars that regularly produces
80% or more large size nuts is the most desirable for the fresh
Trees must produce annual crops of nuts with reasonable cropping
from year to year. A tree that produces too many nuts that can't
size up to premium size is no better than a tree that bears light
crops alternate years.
Time Chestnuts that ripen early (mid September to early October)
are more desirable. They reach the market first, ahead of the
imports and command the premium price. They also avoid the chance
of injury from early fall freezes that could destroy the crop.
Resistance Though Chinese and Japanese chestnuts are our most
blight resistant orchard trees, they often lack nut size, vigor,
form and hardiness. The hybrids overcome these undesirable characteristics,
but may lose some of the blight resistance. Under these circumstances,
the blight may be managed by mudpacking, pruning and using hypovirulent
There are too many selections to mention. A few are included here.
- This is a seedling selection of unknown origin (possibly a Layeroka
seedling). The tree is vigorous and productive. The nuts are sweet,
large and early to mid season ripening. It is moderately resistant
to chestnut blight. It is a good pollinator.
- This is a hand cross of Layeroka x Douglass Manchurian. The Manchurian
is a pure Chinese chestnut that has never blighted. 114W has been
very resistant to blight too, but has the vigor and upright form
needed in a good orchard selection. The nuts are large with some
variability in size, sweet and attractive. It is pollen sterile
and so can't be used without another pollen source.
- This is a selected seedling of Layeroka. It is very early ripening,
starting to drop nuts about mid September. It is a consistent cropper
of large, sweet very attractive nuts. The tree is vigorous and hardy,
but moderately susceptible to blight. It has sterile pollen.
are self infertile. That means that they must have another chestnut
tree nearby with viable pollen to produce nuts. For commercial plantings
a planting plan like the one shown on the following page will help
growers to establish trees with permanent pollinators in place.
If all seedlings are used then a careful distribution of varieties
is not necessary. It is advisable to consider field drainage tiles
between the rows and irrigation for prolonged dry spells of 6 weeks
or more during the growing season.
Click here to
view the Chestnut planting