Know Your Natives – Boott’s Goldenrod

Boott’s goldenrod (Solidago arguta subsp. caroliniana var. boottii*) of the Aster or Sunflower (Asteraceae) family is a medium-size goldenrod with large ovate-lanceolate basal leaves. The genus name is from Latin for “to make whole” or “to heal” in reference to purported health benefits derived from some species of the genus. The varietal name honors Francis Boott, 19th-century American physician and botanist. Boott’s goldenrod, with limited U.S. occurrence, ranges primarily across the western two-thirds of Arkansas, extending into nearby portions of Louisiana, Texas, Oklahoma and Missouri. Preferred habitat is mesic to dry sandy soils in partially shaded woodland openings and borders. It is one of 28 species of goldenrod that occur in Arkansas.

Photo 1: This 3-inch-long caudex bears both 3½ foot tall stems of the current season and short, leafy fall growth. The white shape extending from the base of the right stem is a new rhizome that will terminate with a subsidiary caudex. Photo – mid October.

One to a half-dozen 3 to 4-foot stems with base-diameter of ⅛ to ¼ inch arise from a stout, branched caudex. They are erect to ascending, longitudinally ribbed, and hard and tough with age, with multiple branches, to 2-3 ft long, above. The sunny side of the light green stems and branches becomes reddish brown. Stems are usually glabrous below, becoming appressed pubescent into the inflorescence.

Leaves are borne predominantly toward the base of the plant and are usually present at flowering. Larger leaves below have ovate-elliptic blades to 5½ inches long and 3 inches wide on winged petioles to 5¼ inches long. Leaf margins are sharply toothed. Leaf pubescence is somewhat variable, but upper leaf surface tends to be glabrous while lower surface has short, erect hairs, especially along veins.

Photo 2: This early April photo shows leaves with ovate-elliptic blades and long petioles. Petioles are winged to their base by narrow bands of decurrent blade tissue.
Photo 3: Upper (above) and lower surfaces of larger leaves have irregular pinnate venation.

Median and upper stem leaves gradually become smaller and lanceolate, marginal serrations become less prominent, and petiole length decreases. Leaves near the branch tips are less than ¼ inch long and ⅛ inch wide, sessile, and with entire margins. 

The inflorescence, in September and October, occurs mostly as a panicle with long recurved branches and heads oriented upward. The inflorescence is usually broad and open, less often elongate and narrow. Flowering sequence along the branches is from tip to base.

Photo 4: Flowerheads are secund, i.e., oriented upwards. Racemes and individual flowerheads are subtended by a leafy bract. Note strigose pubescence and small elliptic leaves with entire margins. Photo – early September.

Flowerheads, about ⅜ inch long, are set in elongate, cup-like involucres comprising 3-4 series of spirally arranged, overlapping bracts or “phyllaries”. Inner phyllaries are longer than the outer and transition to bracts along the pedicels. Involucres are nearly glabrous; pedicels and rachises are covered with short strigose pubescence.

Photo 5: The main raceme (left to right across photo) bears short, secondary racemes composed of two flowerheads each, along with a single flowerhead at far right. Phyllaries of the involucres transition to bracts along the pedicels. Photo – early September.

The bright yellow flowerheads have 2-8 pistillate ray florets (with pistils only) which surround up to about a dozen perfect disk florets (with pistils and stamens). Ray florets have strap-shaped corollas with rounded, notched tips and slightly exserted styles with bifurcated stigmas. Disk florets are tubular with 5-lobed corollas and 5 stamens with thin filaments topped with elongate anthers. Anthers are fused into a ring that surrounds the style, which elongates through the anther ring, carrying the pollen above the corolla where it is available to pollinating insects. Once fully exserted, the pair of linear stigmatic surfaces divides and becomes receptive to pollen. Corollas are surrounded by hair-like modified sepals (pappus) which attach to the tip of flat-topped, elongate ovaries.

Photo 6: Flowerheads here have 3-4 strap-shaped ray florets and up to a dozen or so tubular disk florets. The linear stigmatic surfaces of both ray and disk florets are divided. Pistils of disk florets are significantly larger than those of ray florets.

Fertilized florets produce flattened, 1/16 inch long, minutely pubescent, elongate achenes topped by bristly hairs (pappus). The hairs allow achenes to be dispersed widely by wind.

Photo 7: In this late November photo, the gradual decrease of leaf size up-stem into the branches can be seen. Achenes are ready for dispersal on next windy day.

For a garden or natural area, Boott’s goldenrod can add height and bright yellow fall color. This species has a smoother appearance than many of the other Arkansas goldenrods. It is not especially aggressive by seed or caudexes. It is not favored by deer. Flowerheads and leaves are an insect magnet.

Boott’s goldenrod has several general characteristics which help separate it (with difficulty) from the 26 other Solidago species that have yellow flowerheads: 1) one to several tall stems with widely separated leaves, 2) large ovate-elliptic basally disposed leaves, 3) an inflorescence with widely separated straight to recurved branches and sub-branches, 4) secund flowerheads, and 5) overall smooth appearance of the plant.

*Boott’s goldenrod has been identified by Arkansas authorities as Solidago arguta subsp. caroliniana var. boottii. Other authorities have identified it as Solidago arguta var. boottii or Solidago arguta subsp. bootii.

Article and photographs by ANPS member Sid Vogelpohl

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