A word appearing as ᴱQ. telumbe “mushroom” in the Qenya Lexicon of the 1910s under the root ᴱ√TELE “cover in”, along with a longer variant inwetelumbe where the initial element was ᴱQ. inwe “fairy” (QL/42), hence more properly “fairy-canopy” (QL/90).
Neo-Quenya: Since √TELU meant “roof in” in Tolkien’s later writings, I would retain ᴺQ. telumbë “mushroom” for purposes of Neo-Quenya.
A noun appearing as {clumbi >>} G. clummi or clum “mushroom” in the Gnomish Lexicon of the 1910s (GL/26), cognate to ᴱQ. telumbe “mushroom” under the root ᴱ√TELE “cover in” in the contemporaneous Qenya Lexicon (QL/90). It is an example of the sound change whereby tl became cl in Gnomish.
Neo-Sindarin: This sound change occurred in Noldorin of the 1930s but not Sindarin of the 1950s and 60s; compare N. eglenn to S. edlen(n) “exiled” (Ety/LED; PE17/51). To avoid these questions, I would adapt this Gnomish word as ᴺS. telum “mushroom” for purposes of Neo-Sindarin.