Field Thistle, Cirsium discolor

Field Thistle

Cirsium discolor

Benefits:
Sun Shade:
Bloom Time: Fall
Zones: 3, 4, 5
Soil Conditions: Loam
Soil Moisture: Dry, Medium
Color: Purple
Fragrance: No
Height: 6 feet
Spacing: 1-2 feet


Description

Field Thistle, Cirsium discolor, also called Pasture Thistle is biennial or short-lived perennial plant initially forms a low rosette of spiny basal leaves up to 1 foot across. After the first year, this plants bolts and becomes 2-8 feet tall, forming occasional lateral branches that remain erect. The light green stems have white hairs, but they are without spines. The alternate leaves are quite spiny, pinnately lobed, and up to 9 inches long and 3 inches across.

Flower heads with little or no scent occur individually on erect flowering stems in the upper part of the plant. These flower heads are about 2" across and light pink (rarely white), consisting of numerous disk florets. At the base of each flower head, there are overlapping floral that are light green with white central veins; they resemble fish scales. Each floral bract has a single golden spine that is slender, but sharp. Underneath the base of each flower head, there are a few leafy bracts that resemble the alternate leaves, but they are smaller in size and more ascending. The blooming period is from late summer to fall, lasting about a month for individual plants.

The preference is full sun, soil containing loam or clay-loam, and mesic levels of moisture. During summer droughts, there is a tendency for the lower leaves to turn yellow and fall off the plant. This is an easy plant to grow, but it has a tendency to appear rather the worse for wear as the growing season progresses.

Field Thistle can be identified by examining the underside of the leaves; the downy white underside contrasts with the green topside. Non-native thistles do not have this white underside. Additionally, native thistles are noticeably less prickly than weedy, non-native thistles, like bull thistle or Canada thistle


Further Information

Wild Ones of the Fox Valley Area
Prairie Nursery
Wisconsin DNR
Wisconsin Native Plant Nurseries