Early Quenya
lut-
verb. to flow, sail
lutu-
verb. to flow, float, sail
fen
noun. reed
kelu-
verb. to flow
There are more words but they are from Tolkien's earlier conceptional periods. Tolkien likely changed these words as he evolved the aesthetics and completeness of the languages. You may even find languages that Tolkien later rejected. Do not mix words from different time periods unless you are familiar with the phonetic developments.
Below: Tolkien's Late Period (1950–1973). These are from Tolkien's late conceptual period — his most settled forms of the languages. Prefer these over the earlier ones above when composing new text.
A noun in the Qenya Lexicon of the 1910s glossed “reed” under the early root ᴱ√FEŊE (QL/38). It appeared as its stem form feng- “reed” in the contemporaneous Gnomish Lexicon as a cognate of G. feng “(war) arrow” (GL/34).