Oxalis corniculata- eradicate
I have two apple trees that has a lot of Oxalis corniculata. I have been trying to pull it by hand or dig it up & get the roots but it is just getting worse. What herbicide can I use that won't seep into the ground & kill the roots of my apple trees?
Clackamas County Oregon
Thank you for choosing Ask an Expert for help with your oxalis infestation. Because it can spread from roots and rhizomes left behind, plus the numerous seeds in the soil, it is a difficult challenge.
One recommended procedure that might work for you, from the University of California, would be to remove what plants you can. Once done, cover the area with a bark/bark dust mulch about three inches thick. The seeds cannot germinate when they do not get sunlight. A compost mulch is generally too fine and presents a good seed bed for any oxalis seeds that blow in.
Be vigilant. Quickly remove any new plants that come up, and keep the mulch layer topped up, as needed.
There are chemical products available to prevent seeds from popping up and that may be used around fruit trees. If you wish to go that way, contact an arborist or other tree care professional for assistance.
Good luck against this tough weed.