Redflower Ragweed Crassocephalum crepidioides

Thickhead, a weed in the Asteraceae (daisy) family, is a recently introduced summer annual that is very similar to the more common American burnweed (Erechtites hieraciifolius). It can be found growing in abandoned farm land, pastures, orchards, neighborhood gardens, plantations and wastelands. 

It will not flourish in shaded locations or where the landscape is dry.  Full sun and wet conditions are the optimum for spread.

Seedlings form a rosette of elliptic leaves with toothed margins; midveins are often tinged red. Compared to American burnweed, seedling leaves are thicker and more deeply veined. As plants mature they grow upright to about 4 feet with toothed leaves clasping the stem.

The red thickhead flowers lack petals. Additionally, thickhead flowers droop downward as though the plants were experiencing moisture stress. Seeds are wind-dispersed and can produce multiple generations each growing season.

The ability of each plant to produce up to 29 flowers, and each flower sending off approximately 150 wind-blown seeds, makes this plant difficult to control and highly aggressive.  Under the proper conditions, such as those experiences in southern Florida, it can bloom year round.  

Insects, Diseases, and Other Plant Problems:   Due to its weedy nature, eradication via hand weeding when the plant is small works best.  Removal of the flower heads before they bloom can also help to prevent spread of the seeds.  A layer of mulch between the falling/blowing seeds will prevent the seeds from reaching the underlying soil.  Thickhead is managed by most broad-spectrum herbicides. However, herbicide efficacy rankings for this species are based on limited experimental data.