Sometime ago, I noticed these creeping, matting weeds growing between stepping stones in my garden. I thought they were interesting and decided to give them a chance. I'm glad I did not pull them up and let them grow. They have now grown and multiplied and covered the spaces between stepping stones. They help prevent erosion by covering the ground and holding the soil without any help from me — no fertilizing, no watering — that's sustainability at its best. Occasionally, I pull a few of them here and there if they start growing over the stepping stones.

What are these weeds and how do I go about identifying them? As Master Gardeners, we don't know everything, maybe some MGs do, but I don't. But we have access to a lot of research-based information.

One such source is the University of California's Weed Research Information Center website http://weedid.wisc.edu/ca/weedid.php. It has a step-by-step way of helping with weed identification.

First, it asks for the weed type: broad leaf, grass-like or woody. Then it goes to step 2, which asks for different characteristics of the plant. It really helps to have a good size sample of the weed in front of you. About half an hour later, I have a positive ID of my nice weed. (It also helps to have reading glasses or magnifying glasses for quicker identification - I missed the presence of milky sap and some other minute characteristics.)

I found out that my weed is a creeping spurge or matted sandmat (Euphorbia serpens or Chamaesyce serpens).  It is an annual originally from South America. It forms a mat of prostrate stems which root at nodes where the stem comes in contact with the ground. Like all the other plants in the Euphorbia family (e.g., poinsettia), the milky sap is poisonous and at the very least, irritating to the skin. Since it's a groundcover, it's not an issue for me.

So next time you see an unknown plant, don't be too quick getting rid of it. Remember to practice IPM, Integrated Pest Management. Always try to identify it first, then go from there.