What is the best way to kill it?
Kent County Delaware
Marestail is a native plant that is generally considered a winter annual weed. The first leaves that emerge form a basal rosette. As the plant matures it will shoot up a main stem which will bloom and develop seeds. The plants may reach 3 – 6 feet tall. See this website for pictures of marestail at various stages of growth. http://www.ppws.vt.edu/scott/weed_id/erica.htm
Maresatail is easy to dig up or pull up when small. It is also fairly easy to control with herbicides when they are small, in the rosette stage. Herbicides including ingredients such as MCPA, 2-4-D, and dicamba have been effective. When plants are large, and
have begun to bolt or shoot up the main stem, the ability to get effective control with herbicides is greatly reduced. At this stage digging up or at least cutting off the main flowering stem may be the best option for a homeowner. Chemical control would be glyphosate, which may not be completely effective.
When looking for herbicides read the label carefully to make sure it is appropriate for the situation at hand.