I learned a new word, and botanical term. Stipule. If something has stipules, it is stipulate (adjective).

The verb stipulate, meaning to make an agreement or covenant to do or forbear anything; to contract; to settle terms; to bargain, comes from the Latin stipulus meaning firm, which also has roots in stipes, a trunk.

So ultimately both uses of stipulate come from the same trunk, but have very different meanings. I love etymology.