Below is crown vetch (Coronilla varia). I used a foam applicator to spray gobs of glyphosate foam across the plant trying to get good coverage with at least one gob on every inch or two.

The plants coming up through the crown vetch are spiderwort (Tradescantia ohiensis). I was careful not to get any of the glyphosate foam on the spiderwort leaves. Even though glyphosate is not a selective herbicide, the spiderwort was not impacted by the application. This success was surprising to me. Rain often splashes herbicide off onto adjacent plants impacting them. I think the crown vetch softened the impact of the rains so not as much herbicide was splashed off onto non-target plants.

Here is a closer view of one of the spiderwort plants that was under a tangle of crown vetch stems.

I had previously been able to get selectivity using the minimum concentration (about 4 percent a.i.) of glyphosate in the form of foam when I apply it with gloved hands to all the foliage of a crown vetch plant. However, nearby non-target plants showed impacts before recovering the following year.

I find it interesting that directly spraying globs of glyphosate foam of a higher concentration onto crown vetch appears to have killed the crown vetch without visible impacts to non-target species that did not get herbicide directly on them.

Applying herbicide foam from a dispenser directly onto leaves and stems is a lot easier than coating the entire plant using gloved hands. If further testing proves applying a higher concentration of foam directly to plants is effective, while leading to less harm of non-target plants, then I will readily switch to this easier application method.

Either application of glyphosate foam using a gloved hand to fully cover the plant or applying glyphosate foam directly from a dispenser to leaves/stems is much more selective than spraying herbicide. The fine particles from herbicide spray filter through the crown vetch leaves impacting non-target plants below the canopy of crown vetch and herbicide drift impacts taller plants that are nearby. The foam comes out of the dispenser in globs or a stream that sticks to the crown vetch leaves “tenaciously.” The foam slowly liquifies being absorbed into the plant preventing herbicide from dripping off the leaves. So far, applying herbicide foam is the best method I have seen for delivering the herbicide to the target plant while preventing getting herbicide on non-target plants.

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