Have You Seen Thickhead in Your Garden?

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No, I’m not talking about your brother-in-law. Thickhead or redflower ragleaf (Crassocephalum crepidioides) is an introduced weed that I’m observing with more frequency in nursery and garden centers in North Carolina  The species is much more common in the Gulf Coast states and is spreading to other regions in contaminated nursery stock. When vegetative, the plants strongly resemble our native American burnweed (Erechtites hieraciifolius), but has very distinctive drooping, salmon-red flower heads. In contrast, American burnweed flowers are upright and creamy-white. Thickhead seeds are wind-dispersed and germinate anytime from spring through late summer. In container nurseries it can be controlled with preemergence herbicides containing dimethenamid-p, flumioxazin, indaziflam, or oxyfluorfen. In landscape plantings, prevent plants from going to seed and apply a fresh layer of mulch. For more information about this and other weeds of landscapes and nurseries, check out the information on my portal:  Weed Management in Nurseries, Landscapes and Christmas Trees.

upright plant, leaves with ragged margins, white fluffy seedheads

Thickhead growth habit

thickhead salmon-red flowers droop. Seeds have fluffy white pappus for wind dispersal

Thickhead flowers and seedheads

close up of flower heads with salmon-red color

Thickhead flower heads

Written By

Joe Neal, N.C. Cooperative ExtensionDr. Joe NealProfessor of Weed Science and Extension Specialist Call Dr. Joe Email Dr. Joe Horticultural Science
NC State Extension, NC State University
Posted on Sep 6, 2021
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