Somebody contended that tree is not a scientific term. However, Stearn's
Botanical Latin tells us that the Latin word for tree is arbor. He even
declines the word in several directions. It would be rather difficult for a
botanist to describe a new species if he had to say, "It has a single woody,
bark-covered stem, it is 30 feet tall at maturity, and it has branches near the
top," instead of, "It is a tree."
Beyond that, definitions vary. The Wordsworth Dictionary of Botany, 1996
edition, says:
A tall, woody, perennial plant, having a well-marked trunk with few or no
branches
persisting from the base.
The National Audubon Society Field Guide to North American Trees goes into more
detail. I dunno if it is peer reviewed or if you consider it scientific enough.
Their definition:
A tree is a woody plant with an erect perennial trunk at least 3 inches in
diameter at breast height, a definitely formed crown of foliage, and a (mature)
height of at least 13 feet.
I am also including the definition in the Wise Garden Encyclopedia, 1990
edition, although it is not a botanical book per se, just for comparison.
A tree is a woody plant with a single stem or trunk, usually without branches
to a height of 10 feet but crowned at the top with spreading branches, and
growing at least 20-25 feet. There are numerous exceptions...
Now put a chihuahua, a Boston terrier, and an Irish wolfhound together & define
Canis familiaris.
Iris,
Central NY, Zone 5a, Sunset Zone 40
"If we see light at the end of the tunnel, It's the light of the oncoming
train."
Robert Lowell (1917-1977)