As a kid I loved the big Bull Thistles that sometimes appeared in our garden. True, the first year basal rosettes could be painful to a child who, like me, went barefoot as much as she could, but i loved them. I loved their enormous, prickly stature and their gorgeous purple flowers. Thistles have been valued by other gardeners: the silvery biennial Scotch Thistle called Miss Wilmott’s Ghost is a component of the most esteemed British gardens, and some northern gardeners struggle to grow cardoons, a Mediterranean artichoke relative, for their statuesque thistleyness.
Far too few Ontario gardeners know that there are lovely native thistles. The native Field Thistle (Cirsium discolor) has just as lovely a flower as as the non-native Bull Thistle, the plant is almost as large, but it is never an aggressive self-seeder in gardens. Field Thistle is well-armed with prickles, but, unlike the Bull Thistle, the prickles occur only on the leaves and in the axils of the leaves, they do not extend down the stems. This is the easy distinguishing field mark between the native and the non-native: the non-native Bull Thistle has thorns on the stems, the native Field Thistle does not. Field Thistle is found in the wild almost exclusively in very high quality natural sites. It is uncommon in Ontario and I believe it is officially considered Rare in Quebec.
The native thistles are such important nectar sources for native bees and other pollinators that the Xerces Society has devoted a publication just to promoting native thistles and their ecological connections. After the flowers, the high fat, high calorie seeds are very desirable for small birds such as goldfinches. I think you might want to grow a Field Thistle or two in your native plant garden.
I shall be bringing Field Thistle seedlings to the Wesboro Farmers Market’ this Saturday, June 4th. Like so many Thistles, they are biennials. They will flower in their second year and then die, although sometimes they leave small offsets at the base to keep the plant going. They get 5 or 6 feet tall, depending on the soil. They are plants of prairies and sunny meadows, so provide them with lots of sun and well-drained soil. Do be sure to wear serviceable gardening gloves when clearing away the spent flowering stems – the plants are thistles, after all. I think you will be pleased with all the bees and butterflies they attract, and the goldfinches will love you.