Q: I have two hydrangeas that look like they’re displaying signs of Round Up damage from a landscaper. And I mistakenly sprayed brush killer on what I thought were boxwoods but turns out they are gardenias. Will the bushes survive, and is there anything that I can do?

A: This is panic mode for a gardener! Reversing plant death from accidental herbicide damage is possible, but the sooner you can act, the better. Remember that non-selective herbicides (like those containing glyphosate) are meant to kill everything. And they’re referred to as ‘post-emergent’ herbicides, meaning they work once the targeted weed or plant is actively growing. Herbicides may not be as effective on plants that are drought or heat stressed, so you can hope that may be the case with your hydrangea and gardenia, seeing as it was dry up until a few days ago. It can take 4-20 days to realize the effectiveness of a herbicide on a plant, as it works through all the way down to the soil.

Some of the signs of herbicide stress are stunted growth, curling leaves, tissue death or partial dieback. How to slow all of these: first, it may be possible to just prune out the parts of the plant that are showing signs of decline. Always wash misplaced glyphosate off as soon as possible, as the first 30 minutes are critical. You can sprinkle fresh soil around affected plants. It works to absorb the chemicals. And finally, if herbicides got onto the soil surface, rake that soil away and toss it out.

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