Tall ironweed (Vernonia altissima Nutt.) is a perennial with underground, axillary vegetative buds from which new shoots are produced. In a 2-yr study, tall ironweed plants averaged 6115 seeds/plant. Germination of buried seeds increased with increased time of burial. Foliar herbicide applications were evaluated for control of tall ironweed plants in the pre- to early-bud stages of growth. The triethylamine salt or ethylene glycol butyl ether ester of triclopyr {[(3,5,6-trichloro-2-pyridinyl)oxy] acetic acid} was the most effective, providing 93 to 90% control of top growth and regrowth of tall ironweed. The butoxyethanol and propylene glycol butyl ether esters of 2,4-D [(2,4-dichlorophenoxy) acetic acid] alone and in combination with the amine salt of triclopyr also provided excellent control.
