A noun for a “bush” or “low-growing tree” in The Etymologies of the 1930s derived from primitive ᴹ✶tussā under the root ᴹ√TUS (Ety/ÓR-NI, TUS). According to Tolkien, the bush-like trees described by this word include maple, hawthorn, blackthorn, holly, etc. Such trees cannot be called orn “(tall) tree” (Ety/ÓR-NI), but presumably could be referred to with the more general term galadh “tree”.
Quenya
tussa
bush
tussa noun "bush" (TUS)