The towering titans: forget the traditional definition of a tree. There are a few species-11 to be exact-that defy such a mundane description

American Forests, Spring, 2004 by Whit Bronaugh

Any toddler knows what a tree is, but not all adults, including foresters, agree on how to define them. Most definitions emphasize their woody and perennial nature and a single stem near the ground. Arborists, foresters, dendrologists, and big tree hunters also require such plants to achieve a certain size or else be relegated to the ignominy of a shrub.

There are different standards for separating trees from shrubs, but everyone allows Mother Nature to decide how big a tree can grow. Presumably, a woody, single-stemmed, perennial plant with a crown in the stratosphere would still be just a tree.

Imagine if you lined up all the kinds of North American trees by maximum size. When you stepped back to look, here's what you'd see: a row of trees, hundreds of species long, with sizes ranging from 25 points to 1,321 points.

A full third would offer champs that tip the scales at less than 100 points. Within each 100-point range thereafter, the number of champions gradually declines. There are 177 in the 100s, 124 in the 200s, 95 in the 300s, 56 in the 400s, and 23 in the 500s.

We've now covered more than 98 percent of all North American trees but we're not yet halfway through the range of possible sizes. On our imaginary line of trees, from the 25-point northern bayberry to the 597-point noble fir, an imaginary squirrel could easily hop from one tree to the next, with never more than a 15-point gap to cross. Our line gets a little thin in the 600s with only six trees, but they are still fairly evenly spaced, with the largest gap only 26 points wide. But now we are left with only seven trees to cover a span of 622 points!

Perhaps foresters someday will come up with a definition of megatree based on volume, the ultimate but often elusive measure of size. Or maybe there will be separate megatree criteria for height, circumference, and crown spread. For now, we'll use the arbitrary limit of 650 points, which separates the 11 biggest champion trees in America. Here they are, in order of increasing astonishment.

#11 SUGAR PINE

This is the largest pine in the world and, fittingly, it has the largest pine cones. Even if they miss your head, a 2-foot pine cone dropping nearby can give you a Chicken Little moment. The champion sugar pine just reaches megatree size with 659 points. Although much of the surrounding area has been logged, the biggest sugar pine is currently protected in a 10-acre grove of old-growth high above the North Fork of the Stanislaus River in the Sierras of California. You can see and even walk from one side to the other through an old fire scar at the base. It's sobering to pause inside and suddenly realize that the equivalent weight of 50 full-size pickups is balanced directly above your head, with much of its original support missing.

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#10 MONTEREY CYPRESS

In the natural world, this species is restricted to the coast of Monterey Bay where it is often tortured, twisted, and flattened by salt-laden onshore winds. Only where it has been planted and protected farther inland has its megatree potential been realized. The 668-point champion grows beside a country road near Pescadero, California, about 5 miles from the dwarfing coastal winds but still within the protective fog belt, which promotes rapid growth by reducing water loss. The cypress' short, massive trunk stands more than 14 feet thick before branching off in 20 different directions. The biggest Monterey cypress is also notable for having a 116-foot crown spread, second among conifers after the 130-foot crown of the Torrey pine.

#9 CALIFORNIA-LAUREL

It is almost a prerequisite that to reach megatree size a tree must be a conifer. The 674-point champion California-laurel is the only angiosperm to break this rule, although its complex architecture hints that it may have broken the multi-stem rule long ago. But its history of growth is now buried within a trunk 14 feet thick, which with a 119-foot spread and tree-sized mossy limbs, makes for one jaw-dropping megatree.

#8 PORT-ORFORD-CEDAR

A small species range centered in the Siskiyou Mountains of Oregon and California, a quality of wood once deemed incomparable, and an introduced root fungus have conspired to nearly eliminate the Port-Orford-cedar from the megatree category. This species often tops out above 200 feet and stumps have been found measuring 17 feet across, making its true potential well over 800 points! The current champion, in Oregon's Coquille River Valley, is a "mere" 691 points, with a 12-foot thick trunk and a 229-foot height. Since its closest challenger scores only 564 points, the champion Port-Orford-cedar may be the species' last living megatree, itself a shadow of their former greatness.

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#7 COMMON BALDCYPRESS

The common baldcypress is the only megatree east of the Cascades and Sierras, and one of only two that score in the 700s. Some might argue that the champ, which grows in a southern Louisiana swamp, is more monster than megatree because of its double trunk and extreme flare. Only 83 feet tall, the Cat Island baldcypress has a nearly 54-foot circumference that inflates its score to a whopping 748 points. The next largest baldcypress, the old-growth Senator of Longwood, Florida, has 557 points and probably the greatest volume (4217 cubic feet) of any tree in the East. The Senator has little basal flare, so it seems likely that there were baldcypress megatrees before logging. Old-growth baldcypresses have been accurately aged to at least 1,600 years but unless restraint and foresight survive the comings and goings of empires, we may never know their true megatree potential.