Cirsium undulatum
wavyleaf thistle
Overview
Cirsium undulatum is a native perennial thistle in the daisy family growing 1-3 feet (30-90 cm) tall from a deep taproot, with one or few erect, white-woolly stems. The leaves are 2-8 inches (5-20 cm) long, gray-green to white with dense felt-like hairs, wavy-edged, and lined with stiff yellow spines. Large flower heads 1.5-2 inches (4-5 cm) wide sit singly at the stem tips, each a dome of pink to lavender-purple disk florets above a spiny, cobwebby base. The heads bloom from late spring into late summer and draw many bees and butterflies. Seeds carry a plume of tan bristles (pappus) and disperse on the wind. C. undulatum grows in dry prairies, plains, roadsides, and open rangeland across central and western North America, tolerating drought and poor soil through its deep root. Unlike several invasive thistles, it spreads slowly and stays in scattered stands, though its spines make it a problem in heavily grazed pasture and it can self-seed into disturbed ground. The plant dies back to the root each winter.
Native Range
Cirsium undulatum is native to central and western North America, from the Great Plains and Rocky Mountains west to the Great Basin, ranging from Canada south into northern Mexico. It grows in dry prairies, plains, rangeland, and roadsides.Suggested Uses
Cirsium undulatum is used in native prairie, pollinator, and wildlife plantings on dry ground. Its nectar-rich heads feed bees and butterflies, and the seeds feed goldfinches and other birds. The spiny, silvery foliage adds texture to meadow and restoration plantings.How to Identify
Appearance
Size & Dimensions
Height1' - 3'
Width/Spread1' - 2'
Reaches mature size in approximately 2 years
Bloom Information
Pink to lavender-purple flower heads open from late spring into late summer, roughly May to August. Each head blooms for a week or more and draws bees, butterflies, and other insects. Wind-borne seeds with tan bristle plumes follow in late summer and fall.
Detailed Descriptions
Flower Description
pink to lavender-purpleFoliage Description
gray-greenGrowing Conditions
Sun Requirements
Requires 6-12 hours of direct sunlight daily
• Full Sun: 6+ hours of direct sunlight
• Partial Shade: 3-6 hours of direct sunlight
• Full Shade: Less than 3 hours of direct sunlight