Cirsium discolor (Field Thistle)
Cirsium discolor flower

Zone: 3 to 8

Soil: Sand to loam

Light: Full sun

Bloom colour: Pink to lavender

Bloom period: 8 weeks from mid-summer

Height: Up to 84 inches

Moisture: Dry to medium

Attracts: A variety of butterflies and bees are attracted in small numbers. Birds love the seed.

Notes: First of all, do not confuse this native species with the invasive Canada thistle, which actually comes from Europe. The Canada Thistle can spread through its root system and can become quite annoying if not dealt with as soon as they appear. Field Thistle has leaves with white undersides. It is native to Eastern Canada as well as most of the Eastern coast of the USA. Like other plants, it spreads by reseeding but it is not aggressive.

Being honest, it is fair to say that field thistle is really quite ugly and you will not be planting this forb for its aesthetic qualities. Unsurprisingly, the plant is not in demand and it is hard to find it being sold commercially. I shall attempt to explain why this plant deserves more consideration from wildlife gardeners.

The flowers are magnificent. They are much larger than the Canada thistle. Field thistle has a huge wildlife value. Many pollinators are attracted to the flowers including Swallowtails and Monarchs. They flower at a time when Monarch butterflies are fattening up for their long migration and these butterflies will take advantage of the nectar on offer. As the flowers go to seed, it is guaranteed that Goldfinches will show up for their feast. There are many more insects that feed on the leaves including the caterpillars of Painted Lady. The fantastic wildlife show that comes with this plant more than makes up for the not so idyllic appearance.

Field thistle is biennial and monocarpic. In its first year, it grows as a basal rosette. If you have limited space, you can easily grow this plant in pots in the first year. At the end of the growing season, transplant the individual specimens into the spots where you want them to flower the following year. In the second year, they will bolt upwards and flower throughout most of August. After flowering, the plant dies and therefore it is a good idea to sew some seed each year. Make sure that the birds do not eat all the seed. Collect some and mix them with some soil to store over the winter in a cold place. No other treatment is needed.

It is best to grow these plants with as much sun as possible. The plant is top heavy and the extra weight of birds could cause the stems to break. Many hours of sunshine results in thicker and stronger stems. You can grow it in part sun, but ensure it is well supported. Field thistles prefer dry soil. If you have moist soil then consider C. muticum instead. Place it at the back of the bed mixed in with other perennials to obscure the leaves. It can grow over eight feet high so this plant is not easy to place in a smaller garden but if you do have a spot, native thistles make wonderful wildlife plants.



Cirsium discolor
Cirsium discolor after its first year of growth
Cirsium after the first year of growth.
Cirsium discolor with bumblebee
Cirsium discolor
Cirsium discolor flower opening
Cirsium discolor
Cirsium plant
Cirsium discolor
Field thistle with monarch butterfly
Field thistles are popular with Monarch butterflies