Stems, suckers and pioneer species: HCT Winter Tree and Shrub ID class decodes the forest

Leaves tend to leave in the winter, so it can be tricky to identify trees and shrubs. That’s when Harwich Conservation Trust’s (HCT) Winter Tree and Shrub Identification Field Class comes in handy.

Led by naturalist and plant expert Tom Walker, the program, held at HCT’s Sand Pond Woodlands, helped a stalwart bunch of attendees figure out what they are seeing when they take a walk in the woods. Sand Pond Woodlands is a protected 75-acre assemblage hugging the Herring River north of Great Western Road that was made possible by HCT donors and Town Meeting voters.

Harwich Conservation Trust (HCT) naturalist Tom Walker (second from left) guided a group of curious participants on a Winter Tree and Shrub Identification Field Class at HCT’s Sand Pond Woodlands. Photo by Gerry Beetham

“Trees and shrubs are different from herbaceous plants in the fact that they have a lot of lignin,” said Walker. “Lignin is a really tough material. It’s a tough polymer, and it’s what makes wood rigid.” That lignin boost allows trees and shrubs to grow upright.

A tree or a shrub?

A good way to figure out if a plant is a tree or a shrub is by looking at the stem. The general rule is that trees have one stem and can grow to a significant height, while shrubs have multiple stems and tend to be under 20 feet tall.

There are a couple of caveats to that ID methodology: if a tree has been cut down, multiple stems can grow out of the stump, a phenomenon known as “stump sprouts.” And sumacs, a shrub, generally produce only one stem.

Walker also provided an overview of how significant changes in the Cape’s forest have occurred since European settlers arrived on the scene. “When the settlers came, they cut everything down,” said Walker. “When Thoreau came here in 1850, he had a 360-degree view of the ocean and sand was blowing all over the place.”

Without trees to anchor the soil, the humus layer, which holds moisture and organic material, disappeared. “Species that like a deep humus layer really don’t live here anymore,” said Walker.

The rise of pitch pines

Those stripped-down conditions were perfect for pitch pines. “Pitch pines are a pioneer species, and pioneer species love disturbance,” said Walker. “The saplings need full sun and they also need bare mineral soil.”

Inkberry, a member of the holly family, adds shrubby greenery to the forest at Harwich Conservation Trust’s (HCT) Sand Pond Woodlands. Photo by Gerry Beetham

As the forest grows back, less sun is available for shade intolerant pioneer tree species like pitch pines. “Over time, they get taken over by shade tolerant species, like black oak, white oak and maples,” said Walker. “That’s basically how forest succession works.”

What makes Walker’s HCT programs special is the combination of big picture forest topics and in-depth ID information on particular species of trees and shrubs. We learned how to tell huckleberries and high bush blueberries apart — even in winter — by examining the color of their stems.

And we learned that inkberry, a shrub that occupies large swaths of Cape forests, is a member of the holly family that spreads primarily through underground stems called rhizomes, which send up shoots, sometimes known as suckers.

At every stop along the way, Walker was open to questions, both simple and complex. And so, we learned together, spurred by the curiosity of HCT program attendees and anchored by Walker’s impressive knowledge of the forest world around us. If you’ve ever peered into the woods and wondered what’s going on out there, an HCT excursion with Tom Walker will set you on the right path.

Meanwhile, enjoy these images of the experience captured by HCT volunteer photographer Gerry Beetham.

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