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Goldenrods of the Ottawa region

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

  1. 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
    Go to 2

  2. Heads borne in a flat-topped structure; flowers white somewhat like an Aster
    Solidago ptarmicoides

    Heads borne in some other pattern
    Go to 3

  3. Clusters of flowers borne along the stems in the axils of leaves or on short side branches
    Go to 4

    Clusters of flowers borne at the top of the stem on usually downward-curved long side branches
    Go to 9

  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
    Go to 5

  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
    Go to 6

  6. Clumps of flowers borne at the base of the leaves along the stems; woodland species
    Go to 7

    Clumps of flowers borne at the top of the stem on short branches
    Go to 8

  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
    Go to 10

  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
    Go to 11

  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
    Go to 12

  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
    Go to 13

  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.


Euthamia graminifolia (L.) Nuttall
Narrow-leaved Goldenrod, Povertyweed
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
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]


Solidago bicolor L.
Silverrod, Silverweed, Pale Goldenrod
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.



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]



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]



Solidago flexicaulis L.
Zigzag Goldenrod, Broad-leaved 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.



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]



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.



Solidago ptarmicoides (Nees) Boivin

For many years this species was included among the asters where it received the name Aster ptarmicoides (Nees) Torrey & Gray. It is 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" 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.



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.



Solidago rugosa Miller
Rough 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]



Solidago squarrosa Muhlenberg
Stout or Rugged 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.



Solidago uliginosa Nuttall
Bog or 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.


References

  • Gillett, John M. Flora of Gatineau Park. ca. 500 pp. + 79 plates (unpublished).
  • Semple, John C.; Gordon S. Ringius, 1983. Goldenrods of Ontario, Solidago and Euthamia. University of Waterloo Biology Series 26. 84 pages + illus.

This page was created on 6 February 2007
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