Recently our dear friend Cheryl wrote to my husband Phil and I about her lettuce. “Our Romaine has overgrown so it is now a large plant reaching for the skies. I am planning to make an escarole-type soup since I suspect it is now bitter. However, [my husband] is worried that it could be poisonous. What do you think?”
Hmmm. I’ve never found that overgrown, or bolted, lettuce is poisonous. In fact, Phil reminded me that we’ve used it as “a poor man’s substitute for spinach in a stir fry.” (The photo that leads this post shows two of our young neighbors next to some of our own bolted lettuce.) That said, Cheryl’s question was certainly worth a Google search, and everything I read confirmed my hunch that it is not toxic. However, Cheryl was right about bolted lettuce being bitter (see this article from SF Gate).