Populus spp.
Family: Salicaceae
Cottonwood

Cottonwood (the genus Populus) is composed of 35 species which contain the aspens and poplars. Species in this group are native to Eurasia/north Africa [25], Central America [2] and North America [8]. All species look alike microscopically. The word populus is the classical Latin name for the poplar tree.

Populus angustifolia-balsam, bitter cottonwood, black cottonwood, lanceleaf cottonwood, mountain cottonwood, narrowleaf cottonwood, narrow leaved poplar, Rydberg cottonwood, smoothbark cottonwood, willow cottonwood, willowleaf cottonwood

Populus balsamifera-balm, balm of Gilead, balm of Gilead poplar, balm cottonwood, balsam, balsam cottonwood, balsam poplar, bam, black balsam poplar, black cottonwood, black poplar, California poplar, Canadian balsam poplar, Canadian poplar, cottonwax, hackmatack, hairy balm of Gilead, heartleaf balsam poplar, northern black cottonwood, Ontario poplar, tacamahac, tacamahac poplar, toughbark poplar, western balsam poplar

Populus deltoides*-aspen cottonwood, big cottonwood, Carolina poplar, cotton tree, eastern cottonwood, eastern poplar, fremont cottonwood, great plains cottonwood, Missourian poplar, necklace poplar, northern fremont cottonwood, palmer cottonwood, plains cottonwood, Rio Grande cottonwood, river cottonwood, river poplar, southern cottonwood, Tennessee poplar, Texas cottonwood, valley cottonwood, Vermont poplar, Virginia poplar, water poplar, western cottonwood, whitewood, wislizenus cottonwood, yellow cottonwood

Populus fremontii-Arizona cottonwood, Fremont cottonwood, Fremont poplar, meseta cottonwood, valley cottonwood, wislizenus cottonwood

Populus heterophylla-bigleaf cottonwood, black cottonwood, cotton gum, cotton tree, cottonwood, downy cottonwood, downy poplar, river cottonwood, swamp cottonwood, swamp poplar

Populus trichocarpa*-balsam cottonwood, black cottonwood, California poplar, cottonwood, western balsam poplar

*commercial species

Distribution

Most of North America, with Populus deltoides in the eastern to midwest United States and Populus trichocarpa in the western United States.

The Tree

Cottonwood trees can reach heights of 190 ft (77 m), with a diameter of 6 ft (2.4 m).

The Wood

General

The sapwood of cottonwood is white, while the heartwood is light brown to brown. The wood is weak in bending and compression, soft and low in shock resistance. It has a sour odor when wet, but no characteristic odor or taste when dry. Tension wood is frequently present, causing a fuzzy surface when cut.

Mechanical Properties (2-inch standard)

				Compression
	Specific gravity	MOE X10^6 lbf/in^2	MOR lbf/in^2	Parallel lbf/in^2	Perpendicular lbf/in^2	WML^a in-lbf/in^3	Hardness lbf	Shear lbf/in^2
Populus balsamifera (balsam poplar)
Green	0.31	0.75	3,900	1,690	140	4.2	230	500
Dry	0.34	1.10	6,800	4,020	300	5.0	300	790
Populus deltoides (eastern cottonwood)
Green	0.37	1.01	5,300	2,280	200	7.3	340	680
Dry	0.40	1.37	8,500	4,910	380	7.4	430	930
Populus trichocarpa (black cottonwood)
Green	0.31	1.08	4,900	2,200	160	5.0	250	610
Dry	0.35	1.27	8,500	4,500	300	6.7	350	1,040
^aWML = Work to maximum load. ^bReference (98). ^cReference (59).

Drying and Shrinkage

Type of shrinkage	Percentage of shrinkage (green to final moisture content)
	0% MC	6% MC	20% MC
Populus balsamifera (balsam poplar)
Tangential	7.1	–	–
Radial	3.0	2.9	1.2
Volumetric	10.5	–	–
Populus deltoides (eastern cottonwood)
Tangential	9.2	7.4	3.1
Radial	3.9	3.1	1.3
Volumetric	13.9	11.3	4.7
Populus trichocarpa (black cottonwood)
Tangential	8.6	6.9	2.9
Radial	3.6	2.9	1.2
Volumetric	12.4	9.9	4.1
References: 0% MC (98), 6% and 20% MC (90).

Kiln Drying Schedules

	Stock
Condition	4/4, 5/4, 6/4	8/4	10/4	12/4	16/4
Normal wood	T10-C5	T8-F4	T6-E3	T5-D2	–
Wet streaks	T8-D5	T6-C4	T4-D3	T3-D2	–
Schedule for Populus balsamifera (balsam poplar), P. deltoides (eastern cottonwood), P. heterophylla (swamp cottonwood), P. sargentii (plains cottonwood) and P. trichocarpa (black cottonwood References (6, 86).

Working Properties: Cottonwood glues well, has low nail-holding ability, does not split easily, and holds paint well.

Durability: Rated as slightly or nonresistant to heartwood decay.

Preservation: No information available at this time.

Uses: Lumber, veneer, plywood short bolts, pulpwood, boxes, crates, food containers, interior furniture parts, agricultural implements, wooden ware, cutting boards.

Toxicity: Sawdust may cause dermatitis (40, 64, 105).

Additional Reading and References Cited (in parentheses)

6.?Boone, R.S.; Kozlik, C.J.; Bois, P.J.; Wengert, E.M. 1988. Dry kiln schedules for commercial woods-temperate and tropical. Gen. Tech. Rep. FPL-GTR-57. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory.

29.?Elias, T.S. 1980. The complete trees of North America, field guide and natural history. New York: van Nostrand Reinhold Company.

40.?Hausen, B.M. 1981. Woods injurious to human health. A manual. New York: Walter de Gruyter.

49. ?Kennedy, Jr. H.E. 1985. Cottonwood, an American wood. FS-231. Washington, DC: U.S. Department of Agriculture, Forest Service.

55. ?Little, Jr., E.L. 1979. Checklist of United States trees (native and naturalized). Agric. Handb. 541. Washington, DC: U.S. Department of Agriculture, Forest Service. U.S. Government Printing Office.

59. Markwardt, L.J.; Wilson, T.R.C. 1935. Strength and related properties of woods grown in the United States. Tech. Bull. 479. Washington, DC: U.S. Department of Agriculture, Forest Service. U.S. Government Printing Office.

64. Mitchell, J.; Rook, A. 1979. Botanical dermatology: plants and plant products injurious to the skin. Vancouver, BC: Greenglass Ltd.

68. Panshin, A.J.; de Zeeuw, C. 1980. Textbook of wood technology, 4th ed. New York: McGraw–Hill Book Co..

74. Record, S.J.; Hess R.W. 1943. Timbers of the new world. New Haven, CT: Yale
University Press.

86. Simpson, W.T. 1991. Dry kiln operator's manual. Ag. Handb. 188. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory.

90. Summitt, R.; Sliker, A. 1980. CRC handbook of materials science. Boca Raton, FL: CRC Press, Inc. Vol. 4.

98. U.S. Department of Agriculture. 1987. Wood handbook: wood as an engineering material. Agric. Handb. 72. (Rev.) Washington, DC: U.S. Department of Agriculture.
466 p.

105. Woods, B.; Calnan, C.D. 1976. Toxic woods. British Journal of Dermatology.
95(13): 1–97.