Goldenrods are members of the Aster Family. We provide additional detail on this group of wildflowers because of the number of goldenrod species that grow in New Hampshire and the challenge with which one is often faced in attempting to identify a particular species of goldenrod.
The goldenrod group represents as many as 62 species, depending on the source consulted and the geographical area considered. We are unsure how many varieties of goldenrod can be found specifically in New Hampshire, although we are confident that the varieties found include a significant number of the species identified in the various references for wildflowers found in the northeastern United States (New England plus New York, Pennsylvania, New Jersey, Delaware, Maryland, and several other northeastern states).
Gleason and Cronquist generally describes goldenrods as follows: few to many rather small, radiating flower heads in showy clusters; yellow rays except for two species in which the rays are white; seldom more than 25 yellow flowers in the center disk of the flower head; simple, alternate, entire or variously toothed leaves; and stems rounded or squared, and smooth or rough (hairy).
We have elected not to present as many of the goldenrod species as may be found growing in New Hampshire. Frankly, the similarities between many of the species exceed the often subtle differences, minimizing the usefulness of the visuals, with some exceptions.
We first present the Peterson simplification scheme which can be a help in entering the complexity of the goldenrod group. We follow it with a description of goldenrod leaf and flower cluster characteristics.
THE PETERSON GOLDENROD IDENTIFICATION SIMPLIFICATION SCHEME
Although not dispositive in and of itself, the goldenrod identification simplification scheme offered by Peterson (see references) can assist in the voyage through this complex group of plants. Even though the exceptions and crossovers can blur the distinctions that are made, the scheme can be helpful in facilitating identification.
The basis of the Peterson identification scheme is the division of goldenrods into five shape-based categories: (1) plume-like, (2) elm-branched, (3) club-like, (4) wand-like, and (5) flat-topped. Peterson notes that regional variations in the form of specific goldenrod species may occur although hybridization is not considered to be a common characteristic of goldenrods.
1. Plume-like Goldenrods
A "plume" is commonly defined as resembling a feather or a rising column of smoke or dust. For our purposes "plume" includes visual characteristics such as a gentle arching or billowing from a point and around a real or imagined centerline.
Goldenrods that could be placed in this category include Tall Goldenrod, Sweet Goldenrod, Late Goldenrod, Canada Goldenrod, Early Goldenrod, Rough-stemmed Goldenrod, Sharp-leaved Goldenrod, Gray Goldenrod, Bog Goldenrod, and Elliot's Goldenrod.
2. Elm-branched Goldenrods
In elm-branched shaped goldenrods the clusters together form a shape similar to that of an American Elm tree, also often described as an inverted vase:
Goldenrods that could be placed into this category include rough-leaved goldenrod and elm-leaved goldenrod. Two others may take an elm-like shape: Rough-stemmed Goldenrod and Early Goldenrod.
3. Club-like Goldenrods
As the category name implies, these goldenrods tend to be straight and somewhat club-shaped insofar as the profile of the flower clusters is concerned. The shape of the clusters can be somewhat broader than that of the wand-like goldenrods and the individual clusters are not curving. Club-like goldenrods can include the Stout Goldenrod, Showy Goldenrod and Large-Leaved Goldenrod.
4. Wand-like Goldenrods
Wand-like goldenrods have clusters that take on a more slender straight form, longer than they are broad as compared to club-like goldenrods, and tend to be more uniform throughout the length of the cluster. Wand-like goldenrods can include the Blue-stemmed Goldenrod, Hairy Goldenrod, Alpine Goldenrod, White Goldenrod (silver-rod) and Dusty (Downy) Goldenrod.
5. Flat-topped Goldenrods
Goldenrod identification typically focuses on the nature and distribution of the leaves and the nature of the flower cluster (inflorescence).
In some goldenrod species the leaves are inclined to be at the base of the plant, or basally arranged. The lowest stem leaves are relatively large with a definite leaf stalk. Progressing up the stalk the leaves may, but not necessarily, become less populated but typically are smaller in size with reduced or absent stalks, especially above the middle of the plant's stem. The upper leaves also are likely to be of a somewhat different shape from those lower on the stem.
In other goldenrod species the leaves are mainly and distinctly attached to the stem above the ground. Any leaves at the very base of the plant (radical leaves) are small if not inconspicuous. The lowest stem leaves are relatively small and fall from the plant, leaving the stem looking naked at the time of flowering. The largest leaves are well above the plant's base but likely below the middle of the stem. The middle and upper leaves maintain a shape similar to the larger, lower leaves but decreasing in size upward.
Leaf Type. Goldenrods characteristically have simple leaves - the leaf blade is undivided. Goldenrod leaves vary distinctively in shape among the many species.
Leaf Teeth. Goldenrod leaves may be toothless (entire) or toothed and even double-toothed, with the teeth ranging from obscure to sharply present.
Leaf Veins. The leaves of some species of goldenrod are parallel-veined, having smaller veins that begin near the base of the leaf and run parallel to the large mid-vein for the length of the leaf. Other species have feather-veined leaves that are characterized by leaf veins that subdivide into smaller veins branching off laterally from the single mid-vein and somewhat in parallel to one another to the leaf's edge.
Leaf Stalks. Leaf stalks can vary in length or be absent altogether (sessile). Even on the same plant species leaf stalks can be present on the lower leaves and absent on the upper leaves, as noted above.
Other Leaf Characteristics. Leaves of some goldenrod species may be hairy above, underneath, or both resulting in the leaf being rough or smooth depending on the presence or absence of the hairs. The leaves may also have very fine hairs (downy) which, in addition to affecting the texture of the leaf surface, can also cause the leaf to appear off-green.
Goldenrod Flower Clusters
Newcomb (see references) identifies four general types of clusters, or inflorescences, among the goldenrod species. In the first the flower heads are in curved, one-sided clusters which together form a large terminal cluster. This type includes Gray, Early and Rough-stemmed Goldenrods. In the second type the flower clusters are flattish at the top of the plant, from branched flower stems. These are the flat-topped goldenrods such as the Lance-leaved Goldenrod. The third type, which includes Zig-zag and Blue-stemmed Goldenrods, has axillary clusters arising from leaf axils. And the fourth type has flowers in a terminal cluster that is longer than it is broad, and the individual clusters are neither curving nor one-sided, such as the White Goldenrod (Silverrod) and Dusty (Downy) Goldenrod.
Gleason and Cronquist takes a slightly different approach, dividing the flower clusters into three general groups. In group #1, the flower heads are in axillary clusters; or in a terminal, more or less straight, cylindrical, elongate,
narrow, mixed branched cluster or several such branches. In group #2 the cluster is panicle-like (elongated and branched), with at least the lower cluster branches curved, or at a minimum nodding at the tip. And in group #3 the cluster is short and broad, flat
or round-topped, but not one-sided.