At GFE, our south orchard is full of Oxalis pes-caprae, otherwise known as sour grass. This horrible weed originated in South Africa in a climate so similar to ours that it has gone crazy in California, invading everywhere. It’s bright yellow flower and clover-like leaves can be found on roadsides, in restored or disturbed natural areas, parks and gardens. It is relentless and it never sleeps. Many a gardener has spent hours weeding this pest, only to come back a week later and find it fully re-established. So what can we do?