Tuesday, September 6, 2011

Getting a Grip on Goldenrods

One of our most abundant autumn wildflowers, goldenrods are challenging to identify. Some species hybridize and grade into complexes, and individual plants can vary dramatically from the theoretical textbook case. Not only should all of the plant's field marks be taken into consideration, it should also be looked at in the context of its habitat and season.

Unless otherwise noted these photos were taken in early September. Heights are my impressions and estimated heights of the specimens I encountered in the field.

Canada Goldenrod (Solidago canadensis)
Height: Very tall, about 150 cm
Habitat: Relatively wet meadow along the Eastern Ontario Trail

One of our most common goldenrods.

The three prominent veins are characteristic of this species.

The small flowers of goldenrods are less useful for identification purposes, but in some cases the size of the heads or their arrangement can be significant.

Grass-leaved Goldenrod (Euthamia graminifolia)
Height: Tall, about 120 cm
Habitat: Edge of marsh along the Eastern Ontario Trail

The flower clusters and leaves are distinctive; this plant stood out among the neighboring Canada Goldenrod.

Rough-stemmed Goldenrod (Solidago rugosa)
Height: These plants were relatively short, generally less than 100 cm
Habitat: Open wooded areas along the Eastern Ontario Trail

Note the hairy stem and rough texture of the leaves.

The flowers had a distinctly orange cast compared to the more pure yellow of Canada Goldenrod.

The leaves have one prominent central vein; the remaining veins give the leaves a wrinkled quality, especially on their undersides. The upper surfaces have a gritty feel, like fine sandpaper.

Closeups of the hairy stem.

Silverrod or White Goldenrod (Solidago bicolor)
Height: A small plant, perhaps 50 cm tall
Habitat: Very dry, sandy meadow, along a Quinte Conservation Trail about one kilometer southeast of Actinolite.
Photographed: mid August

With its sparse spike of white (occasionally yellow) flowers this small goldenrod isn't apt to be mistaken for another speciers.

A little surprise hidden among the blossoms.

Gray-stemmed Goldenrod (Solidago nemoralis)
Height: Another short goldenrod, most specimens were only 50 cm high
Habitat: Dry upland meadows along the Eastern Ontario Trail

I don't know how this goldenrod got the name "Gray-stemmed", it looks more blue or purple. However, the arching form of the stem with flower clusters borne on the upper side is according to the books.

Again, comparing this plant's blossoms to those of the Canada Goldenrod, the flowers have an almost glowing greenish tint.

Basal leaves are present during flowering.

More Gray-stemmed Goldenrods encountered at another high and dry meadow further west along the trail. To say this species is abundant or ubiquitous would be an understatement.

The undersides of a stem leaf ...

... and a basal leaf.

Bog Goldenrod (Solidago uliginosa)
Height: Small, most were no more 30 cm high
Habitat: Wet, these goldenrods were encountered at the Stoco Fen

The flowering branches tend to grow vertically, following the main stem. These plants didn't bear an abundance of flowers, likely a result of the nutrient poor conditions of their habitat.

Leaves along the upper stem ... note how the leaves clasp the stem, a distinguishing characteristic of this goldenrod.

Views of leaves lower on the stem. (These leaves also clasp the stem but I didn't get any good pictures of this feature.)

Stout Goldenrod (Solidago squarrosa)
Height: Tall, these plants were at least 120 cm in height
Habitat: High and dry hillsides, in woodland clearings along Deer Rock Lake Road north of Flinton

This plant's overall height and flowers borne on short, upright branches stand out in the field. Note that the basal leaves are present during flowering.

The flower heads of this goldenrod are quite large, I've inserted my finger in one of the photos to impart a sense of scale. Also visible are the squarrose or strongly recurved phyllaries – this is a key identifying characteristic of this species.

Photos of the leaves and smooth, hairless stem.

An underside view of an upper stem leaf ...

... a leaf lower on the stem ...

... and a photo of the basal rosette.

Zigzag Goldenrod (Solidago flexicaulis)
Height: These plants were relatively short, from 50 to 100 cm tall
Habitat: Shaded woodland areas along the Eastern Ontario Trail

The broad, deeply toothed leaves and zigzag stem are typical of this species.

The flowers are usually borne on a single upright stem, the ray flowers tend to be sparse.

Views of the leaf.

Wreath Goldenrod (Solidago caesia)
Height: Short, most plants were about 50 cm high or less
Habitat: Shaded woodland areas along the Eastern Ontario Trail

This goldenrod is found in the same habitat and blooms at the same time as the Zigzag Goldenrod. However, the stem of the Wreath Goldenrod has an arching rather than zigzag form, the leaves are lanceolate (lance-shaped) with much shallower teeth, and the flowers grow in clusters from short branchlets at the nodes.

Wreath Goldenrod flower heads are relatively large.

This wildflower is also known as Blue-stemmed Goldenrod. The smooth stems do indeed have a bluish tone – at least on the lower parts of the stem – and are covered in a waxy white bloom that wipes off.

Views of the leaves ... compare to the Zigzag Goldenrod.

Contrary to conventional wisdom goldenrods do not cause allergies. Their pollen is much too large and heavy to be carried on the wind. They rely on insects as pollinators and you'll see a lot of insect species visiting goldenrod flowers.

Goldenrods are popular host plants in another respect. We've already met the fly that causes round goldenrod galls ... Eurosta solidaginis. The goldenrod bunch galls below are formed by a midge, Rhopalomyia solidaginis.

And elliptical galls are courtesy of a moth, Gnorimoschema gallaesolidaginis.