This must surely be "[Eripmav][1]", a (very) short story by Damon Knight, first published in the Magazine of Fantasy and Science Fiction in June 1958.

As the OP recalls it deals with Earth colonising a planet in the Fomalhaut system called "Veegl":

> The  Veeglians,  like  all  higher  life  on  this  world,  are plants;
> the Veeglian vampire, needless to say, is a sapsucker

A Veeglian girl is found complaining of lassitude, and two puncture wounds are found in her neck. The Earthmen find and kill the Veeglian vampire responsible, and the story ends:

> Afterward he seemed dead enough, but the local wiseheads advised us to
> take certain precautions. So we buried him with a steak through his
> heart.




  [1]: http://www.isfdb.org/cgi-bin/title.cgi?57065