Think you have a Big Tree?

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A few months ago I happened upon an enormous cucumbertree magnolia. “Must be the biggest cucumbertree magnolia anywhere,” I thought.

Such speculation doesn’t have to be idle. In a Washington, D.C., office, the American Forests organization keeps the National Register of Big Trees.

The Big Tree program was begun in 1940 as America faced impending war and its need for resources, including wood. The first giant to be earmarked and saved from the threat of a saw was Maryland’s Wye Oak, an estimated 450 years old and, up to its death, the champion white oak.

Since 1940, more than 800 Big Trees have been named. Almost every state has at least one, with the most in Florida and then California. Those states are home to some species found only there.

What’s the biggest?

Not all Big Trees are necessarily big. Each is merely the biggest of its species. The smallest Big Tree is in Texas, a Reverchon hawthorn in Dallas which “soars” to 9 feet tall and around whose trunk you could wrap your hands.

You can probably guess which is the biggest Big Tree: the General Sherman sequoia in California, its upper leaves, at 275 feet, tickling clouds, and its girth, at 998 inches, wide enough to accommodate a two-lane road.

Somewhat unsettling, given its weedy nature, is the image of the largest staghorn sumac, which is 61 feet high. Or one of the two poison-sumac co-champs, 23 feet tall with a branch spread of 21 feet!

Trees with history

It’s fun to imagine what was going on when the sequoia or western juniper champions were still in their relative youth a thousand or so years ago.

A few Big Trees have been more than mere witnesses; they have been part of history. The champion osage orange tree, still standing at the Patrick Henry homestead, was grown from a seed sent by Lewis and Clark to Thomas Jefferson, then presented to Henry’s daughter.

I will now surely pause for thought before planting out my 5-year-old osage orange seedlings this spring.

Competition rules

The Big Tree program is a friendly competition, but like any competition, there are rules. Most obvious is that a Big Tree must be a tree, that is, a plant with a definite crown of foliage topping a trunk at least 3 inches in diameter. It also must be native or naturalized in the continental United States.

Big Trees are measured three ways to give an overall score, which becomes the basis for championship.

First, and most straightforward, is to measure trunk girth in inches. Rules specify taking this measurement at 4 1/2 feet from the ground. If the ground slopes, measure from the high point; if the tree forks at 4 1/2 feet, measure the smallest circumference below that height; if the fork starts lower, measure the largest stem.

Height is a straightforward measure only if you’re a very good tree climber. For an indirect measure, hold a yardstick vertically in your outstretched hand, adjusting its height above your hand to equal the distance from your hand to your eyes. Now walk backwards until the top of the tree lines up with the top of the yardstick and you can just see the base of the tree over your hand – all without moving your head or your hand. The height of the tree, if you stayed on level ground, is equal to your distance away from the tree.

The third measurement is the average spread of the branches. Add the widest spread and the smallest spread, then divide by two.

Get your overall score by adding up the girth in inches, the height in feet, plus one-quarter times the average branch spread in feet.

I’m going to go measure that cucumbertree magnolia, and if it scores higher than 389 points – the score for the current champ, reigning in Waukon, Iowa – then this local tree is a champion. And even if it’s not, it is majestic to behold.

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