Asters and Goldenrods

Aug 02, 2012

By Steve Blight

Now that August has arrived, the dominant colours of the wildflowers of the fields, forests and roadsides are increasingly becoming yellow and various shades of mauve and purple. Given this year’s highly unusual weather it’s hard to predict what kind of late summer and fall wildflower show we’re likely have. However, last week’s modest rains have perked up many local plants so let’s keep our fingers crossed.

Most of the golden yellow flowers appearing in late summer and throughout the fall in our area are goldenrods. In the Ottawa area, botanists have noted 14 different species of goldenrods inhabiting a very wide variety of habitats, and it wouldn’t surprise me to find about the same number in the Land O’Lakes area. My personal favourite goldenrod is the Blue-stemmed Goldenrod (see picture) that is found locally in shady forests.

Goldenrods are often falsely blamed for causing hay fever. I recall as a child my mother patiently explaining to me that goldenrod was a nasty plant that was to be avoided because its pollen made people sick. However, with all due respect to my mother, this is simply not true. The mistake is made (and evidently passed on from one generation to the next) because goldenrods flower at the same time as the real villain – ragweed! Goldenrods have sticky heavy pollen and are pollinated by insects. There is very little goldenrod pollen in the air. Ragweed, on the other hand, has small indistinct greenish flowers with very light pollen grains and is wind-pollinated. Ragweed bad, Goldenrod good!

Asters and goldenrods both belong to the family of plants known as Asteraceae, or the older alternate name Compositae. The blossoms of members of this family of plants are composed of two types of flowers – ray flowers and disc flowers. To the untrained eye, the ray flowers appear to be "petals", whereas the disc flowers appear to be the actual flower. Think of the familiar ox-eye daisy – the white petals are the ray flowers and the yellow centre is made up of a large number of tiny disk flowers.

This arrangement constitutes a very efficient pollination method because the whole flower head acts collectively like a single flower. Insect pollinators are provided with a kind of landing platform and are able to visit many flowers at the same time. Thus the arrangement works both ways – the insects obtain more pollen or nectar with less effort and more flowers are pollinated by the insect.

Curiously, there are also 14 different species of asters in eastern Ontario. Many aster species have disc flowers that start out yellow, and gradually turn purple or brown as the flower ages. You will often find flowers with discs of both colours on the same plant. While most species of asters are some shade of mauve or purple, several local asters have white blooms.

Asters are the source of one of my favourite nature “party tricks”. On nice days in October, asters attract large numbers of bees that seem much focused on the business of gathering pollen and nectar. Many years ago I was watching several busy bees going about their work and I carefully extended a forefinger and ever so gently stroked one of the bees. To my surprise the bee barely seemed to notice that I was touching it. My young (at the time) daughter thought her dad was pretty cool because he could “pet” bees and this has since became part of my standard fall repertoire.

North American asters and goldenrods have long held a place of honour in many European gardens. For people who might like to add some native late summer colour to their landscapes, you may be pleased to know that most asters and goldenrods grow well from seed and once established are vigorously self propagating. Careful with the bees though!

Please feel free to report any observations to Lorraine Julien at This email address is being protected from spambots. You need JavaScript enabled to view it.  or Steve Blight at This email address is being protected from spambots. You need JavaScript enabled to view it.