It looks so harmless, the little yellow flowers, the foliage that could be mistaken for the benign clover or yellow wood sorrel. Don't be fooled. Black medic (Medicago lupulina) is a pernicious, nasty, thuggish weed. It can grow as an annual, biennial, or even as a perennial. I made the mistake of ignoring it while I concentrated on the even worse bindweed (which I eradicated). Now, I've lost the battle for the lawn on the south side of the driveway. It's almost entirely black medic now.
To eradicate it, the roots must be completely removed, which is quite a challenge as the roots break very easily. In addition to spreading by runners, it spreads by seeds, which turn black on ripening, for which is gets its common name.I therefore choose black medic as the worst weed at Squirrelhaven. For other Worst Weed posts, visit Worst Weed Wednesday, brought to you by Dave of The Home Garden.