Milkweeds seed are highly viable and will germinate readily under various conditions. Pappus on seeds allows long-distance travel and can contribute to small patches taking over complete fields. Seedlings become perennial within a few weeks after emergence. One shoot can soon become a large patch with ample subsoil moisture to feed underground roots. If herbicide application is not feasible then clip or cut the flowering parts.
Patch spraying covers only a fraction of the area of a broadcast application.
Patch spraying allows use of higher herbicide rates which means getting milkweed under control sooner and with less expense than broadcast spraying. Research has shown good root kill the spring after application from Roundup and Tordon. Apply at late bud to flowering. Tordon residue will be present for several years after application. Patch-spraying is much less expensive than broadcast applications across entire fields.