Photo-Toby Boyer CCD

Why is it so harmful?

Marestail, also know as horseweed, can grow just about anywhere that is not disturbed regularly. This can be on the side of highways, pasture, and no-till fields. These weeds are very hardy and produce large amounts of seeds, even after being sprayed with herbicide. These seeds are similar to dandelion seeds and are mainly dispersed by the wind. Marestail is know to become herbicide resistant when application in not done efficiently. These plants take over an area and are very troublesome to remove after establishing in the fall months. Crop yields from fields that have Marestail can drop by up to 50% in some cases left unchecked.

How can I identify Marestail?

Use identifying apps like Seek by iNaturalist (On both Apple and Google Play stores).

When unable to use phones, remembering what the plant looks like from pictures and descriptions is best. Immature Marestail grows in a rosette pattern that later has a stem the “bolts” upwards. After this stem grows over 6-inches it can grow a seed head, however, the stem can get up to 4-6+ feet. The leaves are long ovals with scalloped edges at the tip.

Where can I learn more?

Information Sheet by Maryland University-- https://www.jeffco.net/sites/default/files/fileattachments/public_works/page/5813/marestail.pdf

Marestail Management by PSU Extension-- https://extension.psu.edu/marestail-horseweed-management

Managing Herbicide Resistant Marestail by PSU Extension-- https://extension.psu.edu/managing-herbicide-resistant-marestail-horseweed