The 1830 typesetter interpreted weed as an error and replaced it with the phonetically similar reed. The semivowels r and w are acoustically very similar in American English, so it is quite possible that as he was taking down Joseph Smith’s dictation, Oliver Cowdery misheard reed as weed, especially since weed is considerably more frequent in everyday spoken English. Of course, either word will work semantically, but reed is probably the correct choice given that there is a passage in Isaiah that uses the same three key words as in Nephi’s metaphorical “wither even as a dried reed”:
The book of Isaiah was, of course, the major source for Nephi’s extensive biblical quoting in the small plates.
Summary: Retain the 1830 typesetter’s emendation of reed for weed; Oliver Cowdery probably misheard the word as he was taking down Joseph Smith’s dictation.