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Goldenrods of the Ottawa regionJohn GillettCurator 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
The units indicated on the figures represent centimetres.
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. 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]
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.
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.
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]
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 is a plant of rivershores, thickets, woods and open fields. Flowering is from late July throughout August.
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.
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.
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.
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.
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.
Restricted to bogs and fens. It is distinctive by the elongate clusters of flowers with stiff branches. Flowering is in July and August. References
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