Rosette leaves are up to 6 inches long and deeply lobed?

• A. Spotted Knapweed
• B. Diffuse Knapweed
• C. Mediterranean Sage
• D. Canada Thistle

Answer: (A)

Rosette leaves that are up to 6 inches long and deeply lobed point to spotted knapweed because this weed forms a basal rosette with relatively large, deeply divided leaves before it sends up flowering stems. That leaf pattern is a distinctive clue used to identify it early in the season. Diffuse knapweed has leaves that are typically more slender and less deeply lobed, not matching the large, strongly lobed basal leaves. Mediterranean sage shows smooth, lance-shaped leaves that are not lobed, and Canada thistle rosettes have leaves that are spiny and stiff rather than deeply lobed. Recognizing the large, deeply lobed rosette leaves helps distinguish spotted knapweed from these other species and aids early control.