By Sydney Chandler
Cars on the Three-Mile Drive have gradually smashed dropped acorns into a nut-butter, and it’s clear that many oak trees are present. This section of the road is home to scarlet, bur, swamp white, and English oaks. Oak can be identified by leaf shape, bark, and acorns. Retaining these visual clues create an oak search image for future tree identification.
Dreaming of Tree Climbing
Looking upward, leaves of the oak have multiple lobes. Some leaves have pointed tips while others are rounded and smooth. The lobed leaves vary from oak to oak. Bur oak lobes are small close to the stem and flare out from the leaf’s midline. The white swamp oak leaf looks like a mitten for a many-fingered creature.
Bur Oak Leaf
Close examination of the bark shows deep furrows. These grooves run vertically and would be mountain ranges from a bug’s-eye-view. For one dragonfly, the dark heavily-textured surface is a safe spot for a camouflaged rest in the sun.
Dragonfly rests on Swamp White Oak
A third component of the oak search image is acorns. The slightly oblong nuts are smooth and polished. One end resembles a balloon tied off with a neat knot. The other end is covered with an acorn cap or bare to show a circular textured white area. Some acorn caps wrap a simple pattern around like a knit cap. Others are more elaborate and like scraggly fur hats.
Swamp White Acorns
Repetition with these features of oaks helps visitors retain an internal search image. This way, when exploring the rest of the Arboretum, the unique leaves, bark, and acorns will jump out as oak! Where are these features found? Where else are oak present?
Sydney Chandler is a Minnesota Master Naturalist Volunteer.