Bindweed, Wild Morning Glory
Here is another weed I found in the field Friday. Although it has a pretty flower, it is generally considered one of California's worst weeds. It's habit of twining and spreading quickly builds an extensive root system which easily withstands most half-hearted weeding techniques. And the seeds can lay dormant for 50 years! So, if you have it, keep digging the roots out and if all else fails, use soil solarization to kill it.