Charles Ellicott Commentary Psalms 104:16

"The trees of Jehovah are filled [with moisture], The cedars of Lebanon, which he hath planted;" — Psalms 104:16 (ASV)

The trees ... —Better, Jehovah’s trees are satisfied. The parallelism shows what Jehovah’s trees are. The cedar of Lebanon (see 1 Kings 4:33) was the grandest and fairest tree known to the Hebrew; and like lightning and tropical rain, is honored by the epithet most expressive of grandeur. (See Bible Educator, iv., 359.)

The poet feels such trees must have been planted by the Divine hand itself—humans could grow herbs, but not cedars. And here, as proof of the lavish provision made by the Creator for the earth's fertility, he states that even these monarchs of the wood have enough.