Goldenrod (Solidago) is a native wild flower that grows across most of Canada and the US. There are more than 25 goldenrods that are native to Ontario.
The most common goldenrod is Canadian Goldenrod (Solidago canadensis) which is the one you will see growing in fields and ditches as you drive or hike. It is tall, attractive, and the fluffy golden flower spikes are beautiful in the fall. This is the goldenrod I have in my garden. It was existing already on the property.
There are other more well behaved goldenrods that can be introduced. For example, Zigzag Goldenrod (Solidago flexicaulis), Bluestem Goldenrod (Solidago caesia) and Stiff Goldenrod (Solidago rigida). If you plan to introduce goldenrod to your wildflower garden, I suggest you explore these. They should be available at native plant nurseries.
Goldenrod supports more than 100 species of moths and butterflies in their larval stage. In addition, more than 35 species of bees are specialist feeders on goldenrod pollen. During the winter, goldenrod seeds are food for small birds. Needless to say, goldenrod is an important native plant to include in your wildflower garden.
There are however some downsides to having Canadian Goldenrod in your garden. It propagates by both seeds and rhizomes and if left unchecked it can spread and invade other wildflowers you wish to encourage.
In addition, goldenrod emits a toxic substance that can suppress other plants onsite. It can very quickly take over.
For a few years I allowed the goldenrod to grow in my wildflower garden, but eventually, I noticed that everything else was being choked out and my attempts to pull it back were no longer working. I did not want to get rid of the goldenrod altogether because I do appreciate its beauty and its benefits as a pollinator and besides there is lots of it next to my wildflower garden.
The solution for me to was to rid a portion of my wildfower garden of all the plants and rhizomes, dig a trench, and put in a barrier to prevent the rhizomes from spreading.
For the barrier, I used some Tyvek which is moisture barrier used around the exterior of a house. I had part of a leftover roll from our house renovation. However, you could use a piece of siding or anything that will prevent the rhizomes from spreading. I do not recommend cardboard or landscape fabric. The rhizomes will eventually find their way through.
I have added some new wildflowers and hope that I can stay on top of pulling any goldenrod that spread by seed out of this part of my wildflower garden. In the mean time, both the pollinators and I can enjoy the feather golden rod on the other side to the barrier.