Controlling woody weeds
Staying ahead of weeds in the pasture can be a chore, especially woody weeds such as Buckbrush, Black Hawthorn, and Multiflora rose.
"There's just a large underground mass from which you must either deplete the underground storage starches and thereby kill the plant, or create a lethal concentration of a selective herbicide through that large underground mass," says Hagood. "Another aspect of these woody species is it's hard to, if you're talking about selective herbicide, penetrate the bark."
Hagood says you're most likely to have the best control with selective herbicides when the plants are actively moving sugars to the root system.
"These selective herbicides move in the plant with the flow of sugars so you want to apply those things such as that they'll be carried to the underground parts, which are in fact your target of this application," he recommends. "That optimum timing is either in the early bloom stage earlier in the spring, or again in the fall before frost."
If you only prefer mechanical control, remove the top of the plant when it's at its largest. Take off as much as you can above ground. This will cause the most drain on the underground system by forcing the plant to re-grow the top. However, Hagood says the easiest and most beneficial control of woody weeds is with a combination of selective herbicides and mechanical manipulation.
You'll also need patience and persistence. Depending on the species, it may take several seasons to achieve acceptable control.