After digging the oxalis out, bulbs and all, I mulch heavily to discourage more from emerging, but sooner or later they will be back. There are broadleaf herbicides that target oxalis. Some herbicides may kill the oxalis and not kill a desired shrub but cause deformations in the foliage. Image is an herbicide that experts say kill oxalis in beds and on the lawn. However, please read the label carefully as some of the shrubs and ornamentals you wish to protect may be damaged with this product.
Tickets are available at many locations around town.
Mail garden questions to Kathy Huber, Garden Editor, Houston Chronicle, P.O. Box 4260, Houston, Texas 77210. The bulk of mail prevents individual replies to all unpublished letters.