Middle Primitive Elvish
galad
root. tree
galadā
noun. tree
galā-
verb. to grow
gālæ
noun. light
glā
noun. radiance
golā-
verb. to grow
kalat
noun. light
k’lā
noun. light
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.
The basis for Elvish “tree” words, this root first appeared in The Etymologies of the 1930s as an extension of ᴹ√GALA “thrive” (Ety/GALAD). This replaced the earliest derivation of “tree” from the Qenya Lexicon of the 1910s, where the Qenya word for “tree” ᴱQ. alda was derived from ᴱ√ALA “spread” (QL/29). In The Etymologies, the Quenya form of this word remained the same, but the 1910s Gnomish words G. âl “wood” and †alwen “tree” (GL/19) became the 1930s Noldorin word N. galadh “tree” (Ety/GALA). Quenya and Sindarin retained these words for “tree” thereafter, and while Tolkien did not mention the root √GALAD again, his continued use of primitive ✶galadā “tree” (Let/426; PE17/153; PE21/74; UT/266) made it clear this root remained valid.