Plants of the Eloise Butler Wildflower Garden

Giant Goldenrod is a native erect perennial and is a common roadside Goldenrod.

Stems: It grows from 1 to 6 plus feet high. The stem is unbranched below the floral array, smooth throughout but within the floral array there may be sparse short stiff hair. In full sun stems can be reddish in color.

Leaves are all stem leaves, alternate, lance shaped with sharp teeth on the margins, tapering to a pointed tip and tapering to the stem; larger leaves with two noticeable veins parallel to the mid-rib, all 3 rising from the base. Upper stem leaves may be without teeth. Most leaves are sessile (stalkless). The lowest leaves usually wither by flowering time. Mid-stem leaves are the largest, 3 to 5 inches long, then decreasing in size into the floral array. The underside of the leaf may have hair on the main veins and nerves or can be otherwise smooth, but is much paler in color.

The floral array is a spreading pyramidal cluster of arrays at the top of the stem with the flowers on one side of each branch of the array; these branches tend to recurve backward (downward), particularly the lower branches of the array. The branches may have fine hair or be smooth.

Flowers: The yellow flower heads are bell shaped, less than 1/4 inch across, composed of two types of florets: 9 to 15 tiny pointed ray florets, with yellow rays, which are pistillate and fertile, and 7 to 12 disc florets with yellow corollas whose lips are pointed and erect to spreading during pollination. These are bisexual and fertile. The disc florets have 5 stamens with yellow filaments and anthers. The anthers surround and are appressed to the style. Anthers turn darker at pollen maturity. The thin phyllaries are greenish to yellow-green in color and these surround the flower head in 3 to 4 series of unequal size. The outer series lanceolate in shape with pointed tips and the inner series more linear with tips less pointed.

Seeds are dry cypselae, 1.3–1.5 mm long, with a fluffy whitish pappus for wind dispersal. The cypselae are tan and are of a shape called narrowly 'obconic' - that is like a narrow inverted cone. Seeds of Solidago usually require 60 days of cold stratification and light for germination so they should be surface sown.

Habitat: Giant Goldenrod is subject to some interesting galls (see below). The plant can form dense colonies from its creeping rhizomes and from self-seeding. It grows in roadsides, open fields, prairies where there is full to partial sun, moist to slightly dry conditions. This is the same habitat as Late Goldenrod, S. altissima and the two may frequently be found in the same area, although S. gigantea tends to bloom earlier. There may be some hybridization between plants growing in the same vicinity, which will tend to frustrate identification.

Names and varieties: The genus Solidago is from the Latin solido, to 'make whole' as the plants of this genus were known to medicinally "make whole". (see bottom of page). The species gigantea means 'large'. This species is one of the tallest native goldenrods. The author name for the plant classification - ‘Aiton’ is for William Aiton (1731-1793), Scottish botanist, who succeeded Philip Miller as superintendent of the Chelsea Physic Garden and then became director of Kew Gardens, where he published in 1789 Hortus Kewensis, the Garden’s catalogue of plants, which contained the description of this species. Older synonyms for this species are Solidago serotina and Solidago pitcheri.

Comparison: Closely resembling this species is Late Goldenrod, S. altissima. That species has a similar height and root system, but the stems have fine hair throughout except sometimes at the base of the stem. S. altissima has fewer disc florets - 3 to 6 vs 7 to 12 and fewer ray florets - 5 to 13 vs 9 to 15. Its leaves have fewer teeth, the phyllaries tend to be more yellow, but it is also subject to the stem galls explained below.