Witchy Hats on Witch Hazel Are in the Woods Now

Now is a great time to find bewitching sights in the woods of Northern Virginia. Here’s evidence: Witch “hats” on native Witch hazel (Hamamelis virginiana) leaves.

An aphid forms a sooty black gall shaped like a witch's hat on a native Witch hazel leaf.

An aphid forms a sooty black gall shaped like a witch’s hat on a native Witch hazel leaf. Photos by Jo Allen

The conical black “hats” are the chemical reaction of the Witch hazel leaf to an aphid, Hormaphis hamamelidis, that disturbs the leaf surface with its ovipositor, leaving behind a tiny egg. The leaf surface reacts to the injury by building a pointy, black gall of sooty mold with a wide brim over the spot, where the ovum overwinters before emerging in its new form by chewing through the bottom of the leaf. Clever insect, no? Smart leaf, right? Symbiosis! It could be magic, but that’s nature for you—perpetually amazing, clever, and resilient.

Native Witch hazel is flowering now under its bright yellow leaves with witch hat galls in a woods near you. The leaves will be at eye-level, tinged with black, and found on woodland edges, often in areas near water.

Yellow Witch hazel leaves, flowers below, black "witch hat" galls of the aphid Hormaphis hamamelidis on top.

Several witch “hats” are atop the bright yellow leaves of Witch hazel (Hamamelis virginiana) in lowland woods. The native plant hides its narrow flower petals under its leaves.

Witch hazel from any but native-plant purveyors that you might plant in your yard for winter flowers may not be nearly as entertaining as the true native, which puts on its whole show right now: bright leaves, witchy galls, and long-lasting twisted, four-petaled flowers all at once. Don’t miss it!

Where to find it: Native woodlands in lower areas, not hilltops. This one pictured and several more like it were spotted a week ago in Glen Carlyn Park, parking lot at 401 S. Harrison St., Arlington. Walk down the hill in either direction. They’re near the bottom, Four Mile Run, and the W&OD Trail. On the way down or up, admire the many oaks, tall tulip trees, and hickories. The hickories will still have their fat golden leaflets. And for the straight scoop on the long history of Witch hazel, trust Capital Naturalist Alonso Abugattas.

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TreeStewards of Arlington and Alexandria, Virginia, are trained volunteers who work to protect, preserve, and enhance urban tree canopy through public education and volunteer activities such as planting, pruning, and caring for trees.
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