Thick Trees:

(‘ets ‘abhoth (Le 23:40; Ne 8:15)): One of the varieties of trees which the Israelites were directed to use at the Feast of Tabernacles; in the latter passage they are expressly directed to make booths with them. According to the Talmudic writings, the "thick trees" are myrtles (Suk. 12a; Jer Suk. iii, 53d), and further tradition has prescribed certain special features as to the varieties of myrtle employed, without which they cannot be used in the ritual of the feast. In Sirach 14:18 "thick tree" represents dendron dasu, "leafy tree."

See MYRTLE