Hi Toronto Master Gardener! Any suggestions for low and medium height perennials that are great for very heavy clay soil in full sun? Also any suggestions for year-round colour?
Congratulations on wanting to grow native. The benefits of gardening with native plants are many including: attracting native pollinators and birds, easy maintenance and helping to conserve our natural heritage for future generations.
Plants which are able to thrive in clay soil are extremely hardy, and their root systems are strong enough to break through the heavy clay soils and are able to handle the compaction that can occur. Clay soils absorb water very slowly and retain water for a long time. When dry, they harden and become extremely difficult to work. It is always advisable to improve the texture and structure of your clay soil by adding a couple of inches of organic matter, such as mulched leaves, compost, wood mulch. Improving the texture and structure of your clay soil you will be able to plant even more species.
Here are a few that would work:
Bee balm Monarda didyma
Big BlueStem Andropogon gerardii
Little Bluestem Schizachyrium scoparium
Black- Eyed Susan Rudbeckia hirta
Blue Vervain Verbena hastata
Boneset Eupatorium perfoliatum
Butterfly Weed Asclepias tuberosa
Cup Plant Silphium perfoliatum
False Sunflower Heliopsis helianthoides
Blazing Star Liatris spicata
Golden Alexanders Ziza aurea
Goldenrod Solidago spp
Compass Plant Silphium laciniatum
Ourple Coneflower Echinacea purpurea
The North American Native Plant Society also has an excellent site with a Canadian section for northern gardeners at https://www.nanps.org/
Other sites with downloadable brochures which could be helpful to you are:
Why grow Native Plants by The Canadian Wildlife Federation
These Native Plants Love Clay Soil by Landscape Ontario
Lastly, 100 Easy-To-Grow Native Plants for Canadian Gardens by Lorraine Johnson is an excellent resource