by John Gillett
Curator Emeritus, Botany Division, Canadian Museum of Nature
Most of the golden yellow flowers appearing in late summer and throughout the fall in our area are goldenrods. In addition to these familiar yellow flowered species are two other species which are white flowered. Goldenrods form an important and incredibly beautiful part of our local fall flora.
Goldenrods are members of the Family Asteraceae, or the older alternate name Compositae. When you look at a “flower” of these plants you are actually looking at a cluster of literally hundreds of flowers. You will have to look closely to see that the individual flowers are tiny little things (called florets — meaning little flowers) only a few millimeters in diameter. Individual flowers are usually grouped into larger aggregates called, appropriately, heads. Heads are grouped into still larger structures called inflorescences.
Two kinds of flowers are found in the heads of most members of the Asteraceae. The flowers at the inner portion of the head have a symmetrical set of petals (corolla) and these are the disc flowers; the flowers at the margin have an asymmetrical corolla or set of petals which are modified so that they are strap-shaped and are called ray flowers.
Many of the goldenrods can be distinguished merely by looking at the way they are put together. The patterns for many species are quite distinctive.
Goldenrods are often falsely blamed for causing hay fever. The error is made because of the flowering time which is about the same as that of the real culprit — ragweed. Goldenrods have sticky heavy pollen and are pollinated by insects. It is unlikely that this pollen can be air borne to any extent. Ragweed, on the other hand, has very light pollen grains and is wind-pollinated.
The best book on goldenrods is that by John Semple and Gordon Ringius, called Goldenrods of Ontario. Although it purports to cater to the amateur as well as the scientific worker, it strikes me as a trifle too technical for most people. Of more importance is the number of species included. There are 29 species of goldenrods in Ontario. We have 14 goldenrods in the Ottawa District and there are about 32 in Canada.
Key to the two genera and the species of our region
l. Stem leaves grass-like with several parallel veins; heads of flowers in compact clusters, these arranged in a flat-topped structure
Euthamia graminifolia
Stem leaves broader, not grass-like, with one main vein; heads in clusters but if forming a flat-topped structure then the flowers white rather than yellow
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2. Heads borne in a flat-topped structure; flowers white somewhat like an Aster
Solidago ptarmicoides
Heads borne in some other pattern
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3. Clusters of flowers borne along the stems in the axils of leaves or on short side branches
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Clusters of flowers borne at the top of the stem on usually downward-curved long side branches
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4. Leaves and stems very rough to the touch; groups of flowers borne all along the stem, flowers may be white or yellow
Solidago bicolor
Leaves and stems smooth or only slightly roughened
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5. Bracts (little leafy structures found around the individual heads) with recurved tips; lower leaves broad, almost egg-shaped with nearly rounded tips
Solidago squarrosa
Bracts not recurved but flat
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6. Clumps of flowers borne at the base of the leaves along the stems; woodland species
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Clumps of flowers borne at the top of the stem on short branches
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7. Leaves not very wide, certainly no more than 3 cm, lance-shaped; bracts 2 – 5 mm long; usually a bloom on the straight stem.
Solidago caesia
Leaves 6 – 7 cm wide, with coarse teeth, somewhat egg-shaped, and with long pointed tips; bracts 4 – 6 mm long; zigzag stems without a bloom
Solidago flexicaulis
8. Stems finely roughened at least in the area of the flowers; plants of fields and forests
Solidago puberula
Stems smooth, without hairs; plants mainly of bogs or fens
Solidago uliginosa
9. Terminal clusters of flowers usually turned to one side
Solidago nemoralis
Terminal clusters of flowers with long branches that tend to curve downwards
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10. Basal leaves present during flowering; stems and leaves hairless; leaf margins with fine hairs
Solidago juncea
Basal leaves withered at time offlowering; stems hairy) at least below the flower clusters
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11. Underside of the leaves with a central vein and several alternate) curved, lateral veins; hairy along the veins; middle leaves about 1/3 as broad as long and coarsely toothed
Solidago rugosa
Underside of the leaves with a central vein and two almost parallel veins on either side arising from near the base; leaves much longer than wide) almost strap-shaped and finely toothed
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12. Stems smooth, without hairs below the flower clusters, usually whitened with a bloom
Solidago gigantea
Stems short-hairy or rough at least above the middle
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13. Leaves thin, without hairs or only slightly roughened on the veins, sharply toothed; stems sparingly hairy, hairless or becoming so below the middle; small bracts below the flowers 2 to 3 mm long
Solidago canadensis
Leaves firm, densely rough hairy below with spreading hairs; without teeth or if teeth present, widely spaced; stems densely short-hairy below the middle; bracts below the flowers 3 to 4.5 mm long
Solidago altissima
Notes on individual species
The units indicated on the figures represent centimetres.
No illustrations are provided for Solidago gigantea and S. altissima because they are separable only on rather technical characters which cannot be demonstrated on drawings at this reduced size. The illustrations were done by Sally Gadd for my unpublished manuscript, Flora of Gatineau Park.
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Euthamia graminifolia (L.) Nuttall Narrow-leaved Goldenrod, Povertyweed, Grass-leaved Goldenrod Verge d’or graminifoliée Distinctive by its slender leaves and flat-topped inflorescence (corymb). Narrow-leaved Goldenrod is a familiar sight along streams, on beaches, in meadows and in damp soil in open fields. Flowering takes place mid-July until mid-September. A very attractive plant and one of my favourites. [photos of Euthamia graminifolia] |
| Solidago altissima L. Tall Goldenrod, Late Goldenrod Verge d’or très élevée This species occurs in open fields, clearings and along margins of woods. It is relatively common and can be recognized most readily by its densely hairy lower stem, stiff leaves and its greyish cast in the field. Flowering is in August and September. [photos of Solidago altissima] |
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Solidago bicolor L. Silverrod, Silverweed, Pale Goldenrod, Silverrod Verge d’or bicolore Semple includes most of our plants under the name S. hispida Muhl. and indicates that S. hispida and S. bicolor are almost the same thing. As they differ only by the yellow versus white ray flowers, the two phases are considered as two varieties by many authors. The relationship between them is not at all clear. So I am putting them together under the older name. It is found in rocky places, along riverbanks and about cliffs. It is rather sparse in this area. Flowering is from July to August. It is in fruit until mid-September. [photos of Solidago bicolor] |
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Solidago caesia L. Blue-stemmed Goldenrod Verge d’or bleuâtre The arching stems with heads borne at the base of each stem leaf) and the slender tapering leaves are quite distinctive. This is a woodland species flowering from mid-August until late September. Fruiting is in October.[photos of Solidago caesia] |
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Solidago canadensis L. Canada Goldenrod Verge d’or du Canada, Bouqets jaunes Abundant in open fields, often forming dense stands. Flowering is from late July throughout August. This species has thinner and more flexible leaves than S. altissima. The stems are sparingly hairy, without hairs at all or becoming hairy below the middle. Difficulty may be experienced in separating these two species. [photos of Solidago canadensis] |
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Solidago flexicaulis L. Zigzag Goldenrod, Broad-leaved Goldenrod, Zigzag Goldenrod Verge d’or à tige zigzaguante This mixed woods and glade species is distinctive by its tapered, egg-shaped to elliptical, sharply toothed leaves and often elongate flower clusters borne in the axils of the leaves, and its zigzag stem. Flowering is in August and September; fruiting from September onwards. [photos of Solidago flexicaulis] |
| Solidago gigantea Aiton Giant Goldenrod, Late Goldenrod Verge d’or géante Giant Goldenrod is a plant of rivershores, thickets, woods and open fields. Flowering is from late July throughout August. [photos of Solidago gigantea] |
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Solidago juncea Aiton Early Goldenrod Verge d’or junciforme As the common name indicates this is the first goldenrod to come into flower. It can be easily recognized by its broad hairless leaves. Early Goldenrod normally occurs in open meadows and well-drained places. Flowering is from June until October. [photos of Solidago juncea] |
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Solidago nemoralis Aiton Grey Goldenrod, Wood Goldenrod Verge d’or des bois One of my favorite goldenrods (really, all of the goldenrods are my favourites), this species occupies dry habitats, often forming solid stands in fields. It is very similar to S. puberula but that species is restricted in occurrence. Flowering takes place from August to October. [photos of Solidago nemoralis] |
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Solidago ptarmicoides (Nees) Boivin Prairie Goldenrod, White Flat-top Goldenrod, Upland White Goldenrod Verge faux-ptarmica For many years this species was included among the asters where it received the name Aster ptarmicoides (Nees) Torrey & Gray. It was called “Upland White Aster” but as it is now considered to be a goldenrod, perhaps it should be called “Upland White Goldenrod” and “Verge faux-ptarmica” but these are only suggestions as “Verge d’or faux-ptarmica” does not seem right for a white-flowered species. This goldenrod is found in gravel areas and on alvars, which are bare limestone or dolomite pavements with only a small cover of soil. Flowering is from July to September. [photos of Solidago ptarmicoides] |
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Solidago puberula Michaux Downy Goldenrod Verge d’or puberulente Known only from the Mer Bleue area in Ontario but is found occasionally in rocky places and at the edge of woods throughout western Quebec. Flowering is from July to September. [photos of Solidago puberula] |
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Solidago rugosa Miller Rough Goldenrod, Rough-stemmed Goldenrod Verge d’or rugueuse Often forming clumps at margins of woods, this species may occur in fields also. Distinctive by the hairy stems, venation and number of leaves. Flowering is during August and September. [photos of Solidago rugosa] |
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Solidago squarrosa Muhlenberg Rugged Goldenrod, Stout Goldenrod Verge d’or squarreuse The strongly recurved green-tipped bracts surrounding the heads set this species apart. Common in rocky places and in open woods. Flowering is from July to September. [photos of Solidago squarrosa] |
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Solidago uliginosa Nuttall Bog Goldenrod, Marsh Goldenrod Verge d’or des marais Restricted to bogs and fens. It is distinctive by the elongate clusters of flowers with stiff branches. Flowering is in July and August. [photos of Solidago squarrosa] |