22:2in the middle of its street. And on either side of the river was the tree of life, bearing twelve kinds of fruit, yielding its fruit every month; and the leaves of the tree were for the healing of the nations.

in the middle of its STREET.

This is a continuation from the previous verse and is the same street in the CITY as in Revelation 21:21.

There is a discussion among scholars whether STREET is singular or plural. Keith Harris in "The Unveiling" points out that the Greek for STREET has been translated in plural form in other portions of scripture (Matthew 6:5, 12:19; Luke 10:10, 13:26, and 14:21; and Acts 5:15).

And on either side of THE RIVER was THE TREE of LIFE, bearing twelve kinds of FRUIT, yielding its FRUIT every MONTH;

Again, as Keith Harris points out, RIVER could be translated from the same Greek word in plural form (Matthew 7:25,27; John 7:38; Revelation 8:10, Revelation 16:4; and 2 Corinthians 11:26). The implications are that the source of the RIVER is the THRONE and may spread out from there flowing throughout the CITY (previous verse).

Likewise, TREE may be translated from the Greek as plural such as "clubs" in Matthew 26:47 and 26:55; Mark 14:43 and 14:48; and Luke 22:52; as "stocks" in Acts 16:24. Even as we refer to a tree type, say oak for example, we know there are many different kinds of oak trees growing. Compare this verse with Ezekiel's vision in Ezekiel 47:1-12-12.

This TREE of LIFE is the new earth's equivalent of the old earth's TREE of LIFE (Genesis 2:4-9-14 and Genesis 3:22-24). Its fruit probably is not for nourishment (i.e. if new earth residents didn't eat they would die. That can't be because it violates Revelation 21:4 and Revelation 22:5). Rather it is more like spiritual vitamins. If we use Galatians 5:22-23 for example, we get a spiritual dose of "love" for a month. Recall that we have made a link between the Holy Spirit and the RIVER (previous verse), and this could be considered an extension of the work of the Holy Spirit much like water flows up through the trunk into the FRUIT and LEAVES.

The use of MONTH has caused some difficulty to explain because MONTHS on the old earth are timed by the moon. Since the new earth won't have any night or a need for the sun, we wonder whether there is an equivalent MOON in the new heaven and new earth system? We cannot say for sure, but given how precise an eternal God is during the tribulation period (e.g. Revelation 9:5 or Revelation 11:9) on the old earth, we must assume that there is a way to denote time on the new earth. Those intervals must be based upon Jesus' time (verse 13); we just don't know how long He will make a MONTH of time between the Beginning and the End.

and the LEAVES of THE TREE were for the HEALING of the nations.

The term HEALING most likely is more like well being of the nations. Recall in the original Garden of Eden when one ate of THE TREE(s) of LIFE, there was eternal life (Genesis 2:4-9-14 and Genesis 3:22-24). So, too, here, the LEAVES are what sustains NATIONS forever in the new earth. Furthermore, with the Son, Jesus Christ, the focus of the Revelation, we are here given the mechanism by which eternal life (John 3:16) is imparted to the residents.

By the way, it should not be surprising that the FRUIT and LEAVES are edible. That is what is promised to the Ephesus' overcomers (Revelation 2:7).