par palustris » 05 Oct 2007, 14:44
Quelques info a propos des semis de chataigner, désolé pas traduites
FagaceaeCBeech family
Castanea P. Mill.
chestnut
Franklin T. Bonner
Dr. Bonner retired from the USDA Forest Service=s Southern Research Station,
Mississippi State, Mississippi.
Growth habit, occurrence, and use. The genus Castanea, the chestnuts, comprises 11
species of small to medium-sized deciduous trees found in southwestern and eastern Asia, southern
Europe, north Africa, and the eastern United States. Five species are covered in this chapter; only 2
are native to the United States (table 1). American chestnut formerly ranked as one of the most
valuable timber species in the Appalachian region, and the nuts were an important wildlife food as
well as being extensively marketed for human consumption. In the years since the chestnut
blightCCryphonectria parasitica (Murr.) BarrCwas discovered in New York in 1904, the disease has
spread throughout the range of the American chestnut and completely destroyed it as a commercial
species. Many rootstocks still survive and send up multiple sprouts that grow to the size of a small
tree (table 2) before dying. Some of these sprouts occasionally produce a few seeds, but they usually
do not live long enough for significant production (Sander 1974).
Japanese, Chinese, and European chestnuts (table 1) were introduced into the United States
in the 18th and 19th centuries (Anagnostakis 1990; Sander 1974). The Asian species demonstrated
good resistance to the chestnut blight, and breeding programs were started as early as the 1890's to
transfer the resistance to American chestnut (Jaynes 1975). Chinese chestnut, the most promising of
these introductions, has been widely planted throughout the eastern United States, mostly in
orchards for nut production. Allegheny chinkapin is somewhat resistant to the blight and might be
useful as a rootstock in grafting; its other good features are small size, precocity of fruiting, and
heavy seed crops (Payne and others 1994). Breeding for resistance has not been highly successful,
but recent advances in tissue culture offer new promise (Dirr and Heuser 1987).
Flowering and fruiting. Chestnuts are monoecious, but some trees produce bisexual
catkins also (Sander 1974). Unisexual male catkins, 15 to 20 cm long, appear near the base of the
flowering branches. The pistillate flowers occur singly or in clusters of 2 to 3, near the end of the
branches (Brown and Kirkman 1990; Sander 1974), with the female catkins at the base of the shoot
(Payne and others 1994). Flowering begins in April or May in the Southeast (Hardy 1948) and in
June in the Northeast (Sander 1974).
Chestnut fruits are spiny, globose burs, from 2.5 to 7.5 cm in diameter, borne singly or in
spikelike clusters (Sander 1974; Vines 1960). The fruits each contain from 1 to 3 seeds (nuts);
Allegheny chinkapins have 1 seed and American chestnuts (figure 1) have 3 seeds/fruit (Brown and
Kirkman 1990; Sander 1974). The nuts are flattened on one side and range from light to dark brown
or black in color (Brown and Kirkman 1990; Rehder 1940). Nuts of American chestnut are 12 to 25
mm wide and about 25 mm long. The exotic chestnuts bear larger nuts that are 19 to 38 mm wide
(Sander 1974). Food reserves, primarily starch, are stored in the large cotyledons (figure 2). Fresh
nuts are 40 to 45% starch by weight, with very little lipid content (Jaynes 1975; Payne and others
1994; Wainio and Forbes 1941). Seeds ripen in August to October, depending on species and
location (Hardy 1948, Sander 1974). Seed weights are listed in table 2.
Superior strains and hybrids. There are no identified superior strains of native chestnuts,
but many cultivars and hybrids have been developed with the exotic chestnuts, primarily in Europe.
The search for blight-resistant American chestnuts continues, however, with breeding, tissue culture,
and innovative budding and grafting techniques (Ackerman and Jayne 1980).
Collection of fruits. Chestnuts can be picked from the trees, collected from the ground
by hand, or shaken from the trees onto ground cloths. Burs of Allegheny chinkapin do not open
widely, and the seeds are difficult to shake out. Some remain on the trees throughout winter (Payne
and others 1994). Harvesting should begin as soon as the burs begin to split open. The nuts are
intolerant of desiccation (recalcitrant) (Aldous 1972; Pritchard and Manger 1990), so collections
from the ground should be done very soon after dissemination to prevent excessive drying.
Frequent collection is especially important if the weather is hot and dry, as nuts can lose viability
within a week on the ground (USDA 1951). If the weather is wet, Allegheny chinkapins will
sometimes germinate on the trees (Payne and others 1994).
Storage of seed. Because of their recalcitrant nature, chestnuts are normally stored no
longer than 6 months (overwinter). With good care, however, storage for 18 months is not difficult,
and some have been successfully stored for 3.5 years (Jaynes 1975). Immediately after collection, the
nuts should be floated in water to remove trash and immature and damaged nuts. If collected from
the ground in a dry condition, they should be left in water overnight to restore their naturally high
moisture content. Upon removal from water, the nuts should be spread to dry in a cool, wellventilated
place to remove all surface moisture. The nuts should be placed in containers that inhibit
drying, such as polyethylene bags, and stored at 1 to 3 )C; however, the containers should not be
airtight so that some gas exchange between nuts and the storage atmosphere is possible. Moisture
content of the nuts should be about 40 to 45% during storage (Sander 1974). Too much moisture
can result in loss of seeds to microorganisms (Woodruff 1963).
Pregermination treatments. Chestnut seeds are dormant and require a period of cold,
moist stratification for prompt germination. In normal nursery practice, overwinter storage of fully
imbibed nuts at 1 to 3 )C will satisfy the chilling requirement to overcome dormancy. For nuts that
have not been stored moist, or if a deeper dormancy than usual is suspected, then stratification
should be used; 1 to 3 months is the recommended period for American and Chinese chestnuts
(Dirr and Heuser 1987; Jaynes 1975). If nuts are planted in the fall, stratification is not necessary, but
the nuts should be kept in cold storage until planted (Sander 1974).
Chestnuts are commonly infested with the larvae of the seed weevils Curculio sayi
Gyllenhall and C. caryatrypes Bohemon (Gibson 1985). A simple method to kill the larvae is to
submerge the nuts for 45 minutes in water at 52 )C (Payne and Wells 1978).
Germination tests. The standard laboratory testing procedure for European chestnut is to
(1) soak the seeds in water for 24 hours; (2) cut off a third of the seed at the cup-scar end; (3)
remove the testa; and (4) germinate the seeds for 21 days in or on top of sand at the standard test
regime of alternating 20 and 30 )C (ISTA 1993). If only constant temperatures are available, 28 )C is
recommended for this species, which also has no specific light requirement of germination
(Pritchard and Manger 1990). Data are lacking on other chestnut species with this procedure, but it
quite likely will work for any of them. There are alternate procedures for whole nuts. Stratified nuts
of Chinese chestnut have been germinated in a moist medium at 15 to 21 )C; germination reached
100% in 42 days (Berry 1960).
Nursery practice. Chestnuts may be planted in either the fall or in the spring. Nuts that
have been kept in cold storage from the time they are harvested should be planted in September or
October (Sander 1974). Fall-sown beds should be mulched and protected as much as possible
against rodents (Williams and Hanks 1976). Nuts for spring planting should be stratified for 2 to 3
months.
In both fall and spring plantings, nuts should be sown 2 to 4 cm (: to 12 in) deep and
spaced 7.5 to 10 cm (3 to 4 in) apart in rows 7.5 to 15 cm (3 to 6 in) apart in the nursery beds. Nuts
can be either sown or drilled by hand, or broadcast mechanically (Sander 1974; Williams and Hanks
1976). Some growers recommend planting by hand so that the nuts can be placed on their sides to
promote better seedling form (Jaynes 1975). European chestnuts are normally broadcast at a density
of 100 nuts/m2 (9 to 10/ft2) (Aldous 1972). One should expect 75 to 80% germination in beds with
good seeds (Aldous 1972; Sander 1974). A study with Chinese chestnuts found that grading nuts by
size had no influence on time of emergence, although larger seeds did tend to produce larger
seedlings (Shepard and others 1989).
Literature Cited
Ackerman WL, Jayne HT. 1980. Budding the epicotyls of sprouted chestnut seeds. HortScience
15: 186B187.
Aldous JR. 1972. Nursery practice. For. Comm. Bull. 43. London: Her Majesty=s Stationery Office.
184 p.
Anagnostakis SL. 1990. An historical reference for chestnut introductions into North America.
Northern Nut Growers Annual Report (1989) 80: 132B143.
Berry FH. 1960. Germination of Chinese chestnut seed. Northern Nut Growers Association
Annual Report 51: 40B42.
Brown CL, Kirkman LK. 1990. Trees of Georgia and adjacent states. Portland, OR: Timber Press.
292 p.
Dirr MA, Heuser CW Jr. 1987. The reference manual of woody plant propagation: from seed to
tissue culture. Athens, GA: Varsity Press. 239 p.
Gibson LP. 1985. Description and key to larvae of Curculio spp. of eastern United States and
Canada (Coleoptera: Curculionidae). Proceedings of the Entomological Society of
Washington 87: 554B563.
Hardy MB. 1948. Chestnut growing in the Southeast. Northern Nut Growers Association Annual
Report 39: 40B50.
ISTA [International Seed Testing Association]. 1993. International rules for seed testing. Rules
1993. Seed Science and Technology 21 (Suppl.): 1B259.
Jaynes RA. 1975. Chestnuts. In: Janik J, Moore JN, eds. Advances in fruit breeding. West
Lafayette, IN: Purdue University Press: 490B503.
Little EL, Jr. 1979. Checklist of United States trees (native and naturalized). Agric. Handbk. 541.
Washington, DC: USDA Forest Service. 375 p.
Payne JA, Wells JM. 1978. Postharvest control of the small chestnut weevil in inshell chestnuts.
Journal of Economic Entomology 71: 894B895.
Payne JA, Miller G, Johnson GP, Senter SD. 1994. Castanea pumila (L.) Mill.: an underused native
nut tree. HortScience 29: 62, 130B131.
Pritchard HW, Manger KR. 1990. Quantal response of fruit and seed germination rate in Quercus
robur L. and Castanea sativa Mill. to constant temperatures and photon dose. Journal of
Experimental Botany 41: 1549B1557.
Rehder A. 1940. Manual of cultivated trees and shrubs hardy in North America. 2nd. ed. New
York: Macmillan. 996 p.
Sander IL. 1974. Castanea, chestnut. In: Schopmeyer CS, tech. coord. Seeds of woody plants in the
United States. Agric. Handbk. 450. Washington, DC: USDA Forest Service: 273B275.
Shepard E, Miller DD, Miller G. 1989. Effect of seed weight on emergence and seedling vigor of
Chinese chestnut. HortScience 24: 516.
USDA [United States Department of Agriculture]. 1951. Harvesting, treating, storing, and
marketing chestnuts. Beltsville, MD: USDA Bureau of Plant Industry, Soils, and Agricultural
Engineering. 4 p.
Vines RA. 1960. Trees, shrubs, and woody vines of the Southwest. Austin: University of Texas
Press. 1104 p.
Wainio WW, Forbes EB. 1941. The chemical composition of forest fruits and nuts from
Pennsylvania. Journal of Agricultural Research 62: 627B635.
Williams D, Hanks SH. 1976. Hardwood nurseryman=s guide. Agric. Handbk. 473. Washington,
DC: USDA Forest Service. 78 p.
Woodroof JG. 1963. Storing and handling chestnuts. Northern Nut Growers Association Annual
Report 54: 38B40.
Table 1CCastanea, chestnut: nomenclature and occurrence
Scientific name Common name Occurrence
C. crenata Siebold & Zucc. Japanese chestnut Japan
C. dentata (Marsh.) Borkh. American chestnut S Maine to Michigan; S to
S Mississippi & Georgia
C. mollissima Blume Chinese chestnut China & Korea
C. pumila (L.) P. Mill. Allegheny chinkapin Pennsylvania S to central Florida
& W to E Texas & Oklahoma
C. sativa P. Mill. European chestnut, S Europe, W Asia, & N Africa
Spanish chestnut
Sources: Little (1979), Sander (1974).
Table 2CCastanea, chestnut: height, year first cultivated, and seed weights
Year first Height at
cultivated Cleaned seeds/wt
Species maturity (m) in US /kg /lb
C. crenata 10 1876 33 15
C. dentata 20B25* 1800 220B360 100B162
C. mollissimaH 21 1853 50B220 23B100
C. pumilla 15 C 300 136
C. sativa 21 Before 1880 33 15
Sources: Payne and others (1994), Sander (1974).
* Height refers to sprouts from living rootstocks of trees killed by the blight; before the blight this species obtained
heights of 21 to 30 m.
H Bears large crops annually in orchards beginning at about 8 years of age.