Getting rid of alfalfa in planted prairies

Alfalfa often remains as a residue in prairies that have been planted in former ag fields. It can also invade prairies from adjacent croplands.

For years we have been trying to eradicate scattered alfalfa clumps at Black Earth Rettenmund Prairie. Digging has been unsuccessful, which is not surprising since alfalfa is a persistent perennial. You can never dig up all of the underground root system.

We now have a technique that works. We use 20% Garlon 4 diluted in bark oil and carefully spray the bases of the stems (the "basal spritz"). This is analogous to the basal bark technique used for woody plants. Note that the herbicide is confined only to the bases of the stems, and only a small amount needs to be used.

The photos show dead plants surrounded by unaffected "good" plants.

Not only is the basal spritz technique very effective, but it is a lot quicker than digging.

I haven't checked to see if a lower concentration of Garlon 4 would work.

Note that Garlon 4 is the oil-soluble form of triclopyr.

This technique also works well for other perennial weeds that are not rhizomatous, such as bird's foot trefoil.