If you've ever had oxalis in your flower bed, you know just how pesky this weed can be. You can identify the weed with a few key characterists, such as the clusters of beautiful purple flowers it produces. The foliage looks a bit like a clover or shamrock, as illustrated by the image here.
Hand weeding can be effective to control the weed, however the plant produces tubers (roots or bulbs) that break off and stay in the ground when you pull the weed: the leaves will re-appear. You should dig out the oxalis and remove the roots and bulbs using a towel or weeding tool, ideally in the cool season during this weed's active growth stage. Mulch has very little effect controlling oxalis. Weed barriers and landscape fabrics are much better at controlling this weed. Brown cardboard can actually be a highly effective barrier.