Fieldtrips - Jamestown Island

Here's a followup of sorts to my last posting:

Helen Hamilton led an enjoyable walk on Sunday, December 14, at Jamestown Island. The weather was beautiful —almost warm enough to do without a coat, though it was a little chilly by the end. About 15 people showed up, including of course, Dorothy Whitfield—does she ever miss a plant walk?

Identifying trees in winter is often a challenge. You have to look carefully at branching patterns. Are the tree branches alternate or opposite? Bark can be helpful too. The sycamore we saw was obvious with its white and brown mottled bark, and the light-colored bark of the white oak bark is pretty distinctive as well. Helen pointed out that another good way to identify a tree is to look on the ground for clues. Some of the things we found were pecan shells and golfball-sized dark brown fruits under a black walnut.


Something else we occasionally came across were bunches of rachises on the ground under a bare tree. What is a rachis? They're the central stalk of a compound leaf that the leaflets are attached to. Knowing a tree has compound leaves narrows the field of possibilities quite a bit, and if the tree has opposite branching you know you've found an ash tree, like the one we found.

Towards the end of the walk Helen put everyone to the test identifying a mystery tree with green stems, tri-foliate leaves that looked something like poison ivy, and winged seeds that hung in pairs. After much head-scratching by the group, Helen identified it as a box elder (Acer negundo). Box elders are lowland trees that like moist soil, are weak-wooded, and a bit weedy in character. They're kind of interesting because although they are in the maple family, and have the typical maple samaras (winged seeds), they don't look anything like a maple! Here's a picture of one in summer.

A couple of the oaks gave Helen problems. Unlike some trees, oaks can be a little promiscuous, leading to hybrid leaves that have characteristics of two different species. Some of the oaks we saw were cherrybark oak, white oak, willow oak, and a possible black oak hybrid.

Other trees we came across on the island were silver maple, persimmon, sweetbay magnolia, and eastern red cedar. There was also a nice planting of switchgrass by the Visitor's Center. If you have a chance to visit Jamestown Island, ask to see the plant book that Helen put together—there's a copy at the front desk. Many trees have been marked with round metal tags, though some have been removed by woodpeckers, kids and other creatures attracted to bright shiny objects. Many thanks to the National Park Service and Jamestown Island for letting us visit—the views of the river were beautiful!