First appeared in F&SF. Reprinted by Anthony Boucher, Isaac Asimov, Martin H. Greenberg, Joseph D. Olander, Robert Weinberg, and Stefan R. Dziemianowicz.
On an alien planet where plants rule, some plants are vampires, feeding off other plants. They catch the veg vamp in the act and [Spoiler] have to end its life with a steak through the heart.
Minor, played for a bad pun. A better pun is in Damon Knight's highly lauded "Not with a Bang". What's the difference? Probably how integral the pun is to the actual story and how smoothly it flows without impeding meaning on either the literal or metaphorical levels.
Also of note is how Knight telegraphs meaning in his title through inversion. He does the same in "Rule Golden". Even if you catch it, you may not guess his intent.