Chestnuts - Castanea spp.

• Taxonomy, cultivars
• Origin, history of cultivation
• Folklore, medicinal properties, non-food uses
• Production statistics
• Botanical description
• Harvest, postharvest handling
• Contribution to diet, food uses
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Chestnuts belong to the Fagaceae family, genus Castanea. Related genera include Oak (Quercus) and Beech (Fagus).

Four important nut-bearing species:

1. C. dentata - American chestnut. The species is now nearly extinct due to chestnut blight (Endothia parasitica), introduced into N. America in the 1800's; the fungus girdles and kills trees. Trees planted outside the native range (mid-west and west coast) escape the disease and live to maturity. In the eastern US, this species is now and understory shrub, sprouting from the base then dying back when the disease becomes severe. Nuts are relatively small (3-12 g), but said to have the best flavor of the four species.

2. C. mollissima - Chinese chestnut. This is the most important species in terms of commercial production. These are small, spreading trees in cultivation, reaching 40-50 ft in height. It is the most tolerant species in terms of chestnut blight. Nuts are medium-large sized (10-30 g) with good quality.

3. C. sativa - European chestnut. A larger, straighter growing tree (to 100 ft), better for timber than others. Nut size is medium-large (10-25 g); quality is variable among cultivars, from sweet to astringent. Somewhat susceptible to chestnut blight.

4. C. crenata - Japanese chestnut. A small tree (to 40 ft), often with multiple trunks, cultivated by the Japanese for over 2000 years. Largest nuts of Castanea (30 g), but bland, astringent, and difficult to remove the pellicle (kernel covering). Highly resistant to chestnut blight.

5. Hybrids of dentata x mollissima ('Dunstan' is the main cultivar). Supposedly a blight tolerant chestnut with the nut quality of C. dentata; relatively new and untested. These may be male sterile, so need pollinizers.

"Chinkapins" are a group of chestnut species distinguished by having only 1 nut per bur. Several species are native to the southeastern US. Taxonomically, these species are placed in the Balanocastanon section within the genus Castanea, whereas the chestnuts of commerce are in the Eucastanon section.
 

C. pumila - Allegany Chinkapin [SE U.S.; Virginia south]
C. ozarkensis - Ozark Chinkapin [Arkansas, Missouri]
C. ashei - Ashe Chinkapin [N. Carolina Florida]
C. alnifolia - Trailing Chinkapin [Georgia, Florida]
C. floridana - Florida Chinkapin [Georgia, Florida Texas]
These species are small shrubs or trees (6-15 ft) that resist blight by sprouting prolifically and bearing fruit at a young age. The nuts are small, but sweet and nutty flavored, and excellent wildlife fodder.

Folklore, medicinal and non-food uses.

Chestnut wood is highly resistant to rot, and prior to introduction of blight, was used for railroad ties, utility poles, farm fences and barns, mine timbers. Tannin from bark and wood was the prime source for leather tanning. according to Jaynes, "hogs were regularly turned loose in Appalachia each Fall to fatten on chestnut mast (fallen nuts)".

From species 2-4, above: 521,574 MT (1999 FAO)

 1. China - 20-25%                4.Turkey - 13%
 2. Korea  - 20-25%              5. Japan - 6-7%
 3. Italy - 13-16%                   6. Spain - 4-5%

United States - Production insignificant, no records. Few, scattered orchards or single trees of Chinese chestnut exist throughout North America, and a few European chestnut orchards are found on the west coast.

Botanical description

A. Plant: Tree descriptions are given above. Leaves are oblong-lanceaolate, acute tips, dentate or serrate margins with rather sharp teeth, dark green above and lighter below, sometimes with pubescence on the underside. 

B. Flowers: Monoecious; borne in erect catkins, borne laterally in leaf axils on current season's growth; borne near the base of distally borne catkins, which are bisexual (polygamomonoecious). Each female flower contains usually 3 free carpels, each of which can develop into nuts; hence, 1-3 nuts are found within each spiny "bur" (involucre). The bur splits into 2-4 valves at maturity, exposing the nuts.

C. Pollination: by wind and insect to a lesser extent; most chestnuts are self-unfruitful, and some set burs parthenocarpically (without nuts!) without pollination - pollinizers are necessary in most cases.

D. Fruit: a nut; fairly large, brown, with a large, pale hilum or basal scar at the proximal end, and pointed (± haired in American) at the tip. Resembling a large, rounded acorn in some species. American chestnuts are the smallest, and Chinese & European the largest of the 4 species. The chestnut differs from other edible nuts in being high in starch and moisture content, low in oils (fat), and containing more than 1 nut per involucre. The are generally boiled or roasted to improve flavor and digestibility.

Harvest, post-harvest.

Chestnuts are harvested by collecting from the ground after falling naturally. The nuts are removed from burs and dipped into hot water ( 68°C) for 1 hr to eliminate surface molds.

Fresh nuts @ 50% moisture can be stored for 8 weeks at 40°F, or dried to 10% moisture, they can be stored for a year. Dried nuts are re-hydrated by soaking or steaming prior to use; they become hard and inedible if stored long.

Nuts are eaten raw, or more commonly after boiling or roasting. Major uses are candies, stuffing for Thanksgiving turkeys, and in Italy, they are ground to fine flour for confectionery; in fact, prior to maize introduction to Europe, Italian polenta was made from chestnut flour (polenta is like Italian grits).

Dietary value, per 100 gram edible portion: (fresh)

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Water (%) ........................................... 52
Calories ............................................ 194
Protein (%) ........................................... 3
Fat (%) ................................................ 1.5
Carbohydrates (%) .............................. 42
Crude Fiber (%) .................................... 1.1

% of US RDA*
Vitamin A ............................................. ---
Thiamin, B1 ....................................... 23
Riboflavin, B2 .................................... 24
Niacin ................................................ 6.7
Vitamic C .........................................  ---
Calcium ............................................. 6.5
Phosphorus ...................................... 20
Iron .................................................. 33
Sodium ............................................. ---
Potassium ........................................ 19

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* Percent of recommended daily allowance set by FDA, assuming a 154 lb male adult, 2700 calories per day.

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