Flute

flute [ floot ] noun: a vertical fold or groove in the stem of a tree

Smooth bark and a fluted trunk, a distinguishing genetic characteristic, give native Carpinus caroliniana (American hornbeam) a sinewy appearance leading it to be referred to as muscle wood. Thin, shredding bark is a commonly mentioned feature of native Juniperus virginiana (eastern redcedar); less noted is its oft fluted trunk. Although genetics may be responsible for the fluting in some trees, flutes might also result from environmental factors.

The bark of American hornbeam has a distinctive fluted appearance

Fluting of native Juniperus virginana (eastern redcedar)

Fluting and buttress roots of a native Quercus (oak)

Fluting of native Taxodium distichum (bald cypress, baldcypress)

Left to right: Carpinus caroliniana, Juniperus virginana, Quercus, Taxodium distichum.

Erratic radial growth produces flutes, which may spiral downward from where a branch connects to the trunk or upward from the root collar, usually in the butt of the tree (the first 16 feet). In the case of buttress roots, Kent Julin defines ‘flutes’ as the valleys between the ‘spurs’–the ridges of the buttress that join the main trunk to the large lateral roots (Dean et al. 2018). Buttress roots are typical to shallowly rooted trees in tropical forests, but also can be found on large, old trees in temperate climates to stabilize them.

Fluting and buttress roots of Taxodium distichum (bald cypress) in deep water in Sandbridge, Virginia. — Fluting and buttress roots of *Taxodium distichum* (bald cypress)
in water. Photo © Elaine Mills

Fluting of Tsuga heterophylla (western hemlock) — Fluting of *Tsuga heterophylla* (western hemlock). Photo courtesy of the USDA Forest Service

In the western United States, especially along the southeastern Alaskan coast, fluting is common in hemlock (Tsuga heterophylla) stands and may occur from tree root to crown. Although these western hemlocks appear to possess a genetic predisposition to fluting, “catastrophic disturbances such as clearcutting or windthrow” may contribute to this condition (Julin and Farr 1989). In the east, native Taxodium distichum (bald cypress, baldcypress) trees can develop butt swell as they age. They are usually deeply fluted with substantial roots to provide stability and wind firmness in wet areas.

Fluting can reduce a tree’s lumber value, especially if the flutes are deeply incised into the butt. On the other hand, they may provide habitat for insects and thereby food for birds.

References

Dean C, Kirkpatrick JB, Osborn J, Doyle RB, Fitzgerald NB, Roxburgh, SH. 2018. Novel 3D geometry and models of the lower regions of large trees for use in carbon accounting of primary forests. AoB PLANTS, 10(2): ply015. doi: 10.1093/aobpla/ply015.

Julin, KR, Farr WA. 1989. Stem Fluting of Western Hemlock in Southeast Alaska. U.S. Department of Agriculture, Forest Service, Pacific Northwest Research Station. (accessed December 28, 2020).

Kennedy HE. 1972. BALDCYPRESS. FS-218. U.S. Department of Agriculture, Forest Service.

Mulvey R. Hemlock Fluting. U.S. Department of Agriculture, Forest Service, Alaska Region. [updated 2018].

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