Solidago altissima ssp.altissima

Native

Moist to dry. Prairies, fields, ditches, roadsides, and forest openings. Full to partial sun.

August to October

Yellow ray florets, yellow disk florets

20″ to 78″

This is a 20″ to 78″ tall, erect, perennial forb that rises on 1 to 40 or more stems from branched, short or long, creeping rhizomes. It can be 20″ to 78″ tall, but is usually at least 40″ tall. It often forms large, dense patches. The roots and leaves exude toxic chemicals that inhibit the growth and survival of competing species (allelopathy). Fresh plants have a grayish-green appearance due tothe short hairs on the leaf surfaces.

The stem is erect or ascending, finely grooved, and leafy. It is not shiny and not covered with a whitish, waxy bloom (glaucous). It is moderately to densely covered with short, curved hairs both above and below the middle, though less densely hairy or almost hairless near the base.

There are no basal leaves. Stem leaves are alternate, somewhat thickened, and stiff.

Lowermost stem leaves are narrowly inversely lance-shaped, 3¾″ to 5⅞″ long, and ⅝″ to ¾″ wide, mostly 5 to 13 times as long as wide. The leaf blade is distinctly 3-veined, with a prominent midvein and 2 finer, lateral veins that originate well above the base. It tapers gradually to the base and is attached to the stem with a very short leaf stalk or with no leaf stalk at all. It tapers to a sharp point at the tip with straight or concave sides along the tip. The upper surface is moderatley rough due to the presence of minute, stiff hairs. The lower surface is moderately to densely covered with short, sharp, stiff, appressed hairs, especially along the midrib and main veins. The margins are either entirely untoothed or are untoothed near the base and with sharp, forward-pointing teeth above the middle, and are sometimes turned under. Lower stem leaves are usually absent by the time the plant is in flower.

Middle and upper stem leaves are similar to lower stem leaves. Middle stem leaves are inversely lance-shaped, 1¼″ to 6¾″ long, usually no more than 4″ long, and ¼″ to 1″ wide, usually no more than ⅝″ wide. The margins are finely toothed with 0 to 14, usually no more than 6, teeth per side.

Upper stem leaves are narrowly lance-shaped, 1″ to 2¼″ long, and ⅛″ to ⅝″ wide, usually no more than ⅜″ wide, becoming smaller as they ascend the stem. The margins are usually untoothed, sometimes minutely toothed above the middle.

The inflorescence is a pyramidal, 2″ to 11¾″ long, ¾″ to 9⅞″ wide, usually dense, sometimes open, many-branched, broad cluster with 100 to 1200 or more flower heads. The longer flowering branches are arched or nodding. The flower heads are arranged on the upper side of the branches.

The tiny flower heads are less than ¼″ wide. They have 5 to 17, usually 8 to 13, yellow ray florets. They have 2 to 9, usually 3 to 6, yellow disk florets. The whorl of bracts surrounding the base of the flower head (involucre) is ⅛″ to 3 ⁄16″ long and yellowish in color. The corolla is ⅛″ long.

Canada goldenrod (Solidago canadensis var. canadensis) stems are hairless or sparsely hairy from the middle to the base. The leaves are thin, not stiff. The involucre is shorter, 1 ⁄16″ to ⅛″ long. Fresh plants do not have a grayish-green appearance.

Early goldenrod (Solidago juncea) stems are hairless.

Giant goldenrod (Solidago gigantea) stems are hairless and sometimes covered with a whitish, waxy bloom.

Harger’s goldenrod (Solidago canadensis var. hargeri) leaves are thin, not stiff. The flower heads have fewer disk florets, 2 to 4. The involucre is shorter, 1 ⁄16″ to ⅛″ long. It has been recorded only in Grant County in western Minnesota.

Missouri goldenrod (Solidago missouriensis) is a shorter plant, no more than 32″ tall. The stem is hairless below the inflorescence. Lower stem leaves are on winged leaf stalks up to 2″ long. The upper and lower leaf surfaces are hairless. A tight bundle of small, wing-like leaves often appear in the leaf axils. The flower heads have 8 to 20 disk florets.

Salebrosa goldenrod (Solidago canadensis var. salebrosa) stems are hairless or sparsely hairy from the middle to the base. The leaves are thin, not stiff. The involucre is shorter, 1 ⁄16″ to ⅛″ long. The flower heads have more disk florets, usually 5 to 11.

Taxonomy
Some sources, including NCBI and UniProt, classify this Solidago canadensis var. scabra. Other sources, including GRIN, ITIS, The Plant List, and most older sources, classify it as Solidago altissima ssp. altissima. According to FNA, two factors argue for distinguishing this plant at the species level. First, young plants can appear grayish-green due to short hairs on the leaves, a character not seen in Solidago canadensis. Second, the goldenrod gall fly (Eurosta solidaginis) produces large galls on this plant but not on Solidago canadensis.