Bolting Lettuce: When to Harvest and Remove

A user grew a plant from seed thought to be lettuce/mesclun. It has loose lamb's ear-like leaves, long stems with small yellow flowers. Flea beetles are eating it. Unsure if it's a weed or vegetable and how to harvest.

Expert Answer: The plant is lettuce/mesclun that has bolted. These are biennials: they grow edible parts one season, then after a cool period (winter) they flower (bolting). They lose the head and shoot up flowering stalks. At this stage, they are useless as vegetables and should be removed.