Slug Tales from Zone 6: Identifying native trees

By Soncirey Mitchell
Reader Staff

Trees far outnumber people here in North Idaho, and that’s the way residents like it. Still, even though they’re our neighbors — while providing heat, building materials, shade and defining the idyllic landscape — many people don’t outright know how to tell the difference between, say, a ponderosa pine and a western white pine. For anyone curious about our evergreen (or leafy) companions, here’s a simple guide to some of the most common native species.

Western redcedar (Thuja plicata)

As is common with many plant species, what we call “cedar” isn’t a cedar at all. Western redcedar is a member of the cypress family, and doesn’t look anything like the true cedars native to the Mediterranean and western Himalayas, though they all share a spicy smell. These trees can reach heights of 160 feet with trunk diameters of two to eight feet, growing steadily over their possible lifetimes of more than 1,000 years. Western redcedar’s bark grows in long, fibrous strips that run vertically up the trees, transitioning from a brown-red to gray as they age. Rather than needles, redcedar grows scale-like leaves that fan out and remain evergreen throughout the cold months. Their cones are petite — about two centimeters long — and grow in clumps toward the ends of their boughs. You can find Western redcedars in mixed coniferous forests, growing in moist sites like ravines and swamps.

Ponderosa pine (Pinus ponderosa)

One way to identify ponderosa pines is to remember that their characteristics have the same alliteration as their name: prickly and puzzle piece-like. Their reddish bark is made up of layers of thin, irregularly shaped flakes that resemble puzzle pieces. Their large cones are typically three to six inches long and covered in sturdy, outward-facing spikes that prick your fingers when you try to pick them up. The ponderosa pine’s needles grow in broom-like tufts made up of five- to 10-inch needles growing in groups of three. These trees live for 300-600 years, reaching heights of 120-180 feet, and often plant themselves on dry southern slopes.

Western white pine (Pinus monticola)

Pop quiz: What’s Idaho’s official state tree? Admittedly, the title of this section gave the answer away. Western white pine grows all across the state in low and middle elevations, either in clusters or intermixed with other evergreen species. Mature tree bark takes on the appearance of dried mud or alligator scales, separating into thick, relatively square pieces with large fissures between them. Their needles average two to four inches in length and sprout in bundles of five, fanning out from the ends of smaller branches. These iconic Idaho trees can live for approximately 350 years, reaching heights of 180 feet but remaining relatively thin, with trunk diameters of 2.5-3.5 feet. The most surefire way to identify a western white pine is by its banana-shaped cones, which can grow up to 10 to 14 inches long and have relatively soft, flexible scales.

Western paper birch (Betula papyrifera)

Idaho has native deciduous trees, too, which mostly grow along riparian zones, helping protect shorelines from erosion. One of the most recognizable of these species is the western paper birch, which starts out with dark brown bark that eventually lightens to a chalky white, curling into thin, papery ribbons. Their leaves are teardrop-shaped with serrated edges and alternate on the left and right sides of each branch. Birch trees store their seeds in drooping flower clusters called catkins, which resemble long, green-yellow worms. In the grand scheme of trees, paper birches don’t live very long — about 80 years — and only grow to be around 70 feet tall with slender, one- to two-foot diameter trunks. You’ll find them near bodies of water, growing mostly among their own kind.

Black cottonwood (Populus balsamifera ssp. trichocarpa)

Finally, most people know black cottonwoods from the storm of fluffy “snow” they release in late spring and early summer. They grow along bodies of water or in moist, mountainous woods, generally among other cottonwoods, as they cannot stand the shade from other trees. Though they only live approximately 120 years, black cottonwoods reach heights of 60-120 feet, meaning they grow like weeds wherever they find the space. Even when they aren’t releasing clouds of sneeze-inducing lint, you can identify a black cottonwood by its gray-brown bark that develops deep ravines as it ages, which travel vertically up the tree. The trunk is generally free of branches until the crown opens up, revealing simple, teardrop-shaped leaves that alternate in a spiral pattern around small branches.