A Testimony of Jesus Christ: A Commentary on the Book of Revelation is unavailable, but you can change that!

Studies in Revelation—The Final Revelation of Christ.

3.22.2 - Revelation 22:2 [LISTEN] In the middle of its street, and on either side of the river, was the tree of life The Greek lacks the article: the tree. There are several trees, each of them a tree of life. “It was not one individual tree, but a particular tree as to its kind, as we speak of ‘the apple’ or ‘the oak,’ denoting a species of which there are many specimens.”3002 There may have been exactly three trees, or John saw three groups of trees of the same kind in each of the three areas.
Revelation 22:2