Honoring Stacy Iwanicki | Native Plants of Volo Bog: Winterberry Holly

We continue our tribute to Stacy Iwanicki, the DNR naturalist who has devoted over 35 years to Volo Bog, with our third post in this series. This time, we're featuring Stacy's article on Winterberry Holly from the Bog Log. Perfect timing: winterberry holly is at its peak right now at Volo Bog! The brilliant red berries are pressed against the stems in the tall shrub zone, creating stunning splashes of color against the fall landscape. Stacy's article offers wonderful insights into the plant's ecology and the fascinating (sometimes tipsy!) behavior of the birds that feast on its berries. Please read Stacy's complete article and discover why this native wetland plant is such an important part of Volo Bog's ecosystem.

Winterberry Holly Ilex verticillata

While the days shorten and the nights cool, autumn's palette descends upon Volo Bog. As the school year gets underway, tickseed sunflowers shine like little suns along the boardwalk and poison sumac takes on varying shades of maroon, red, orange and yellow. With the approach of Halloween, the tamaracks begin to turn to gold. In the midst of all these changes is the reddening of the winterberry holly berries. Pressed against the stems, they will remain on the shrubs long after the leaves have fallen. Probably due to their relatively low fat content, the berries are not a preferred food source for birds. Persisting into winter, the berries add color to the first snowy days of December, and it usually won't be until January that the birds will pick off the last of them.

Although they are not a favorite food, many bird species will feed off the interberry holly berries. Flocks of cedar waxwings will partake in the feast first, filling the autumn air with their high-pitched zeeeeees as they dine. Other birds that occasionally consume the berries include bluebirds, thrushes, thrashers, catbirds, mourning doves, flickers and white-throated sparrows. Robins, who prefer a higher alcohol content in the berries, wait until later in the season and literally get drunk as they indulge themselves. This becomes evident as they fly along the boardwalk. Like their human counterparts, their daring increases as they become inebriated on their treat. It is not uncommon to observe drunken robins in kamikaze flight playing chicken with pedestrians who happen along. No collisions have occurred thus far, but be prepared to duck! When I first observed this phenomenon, I thought my imagination was exaggerating my experience, but last year I heard of similar behavior among robins in Florida. I'm not quite sure what they were eating down there...

Winterberry holly is a shrub of wetlands. Tolerating standing water, they begin to dominate amongst the ghostly spires of tamaracks that drowned years ago. Toward the outer periphery of the shrub zone, winterberry dies off, giving way to the great variety of marshland plants as natural succession marches on. It can be recognized by its rather crisp 2" leaves that have variably fine serrations along the edges. The shrub is dioecious, ie.- male and female flowers are borne on separate plants. Flowering in June, the males are distinguished by the pollen on the pistils. The pollen actually gives the whole shrub a yellowish tinge that can be seen from a distance. The female flowers may be recognized by the sticky nectar at the base of the stigma, and the fertilized female flowers will form the berries. Both flowers attract honey bees and other pollinators who give the tall shrub zone its own early summer hummm. The sound is so low in frequency that it is more felt than heard. By July, little green berries can be seen forming up against the stem. They will grow a bit throughout the summer then begin to show signs of turning orange in the fall. By October, they will lend their bright red hues to the tall shrub zone of Volo Bog.

A plant of many aliases, Ilex verticillata is variably known as common winterberry, northern holly, Michigan holly, redberry, inkberry, blackhaw, Christmasberry, fever bush, black-, striped-, white-, and false alder. Here is a good example of why scientific (Latin) names are so important. Although there are other species that share some of winterberry's common names, such as black alder (Alnus rugosa) or have similar names such as Christmas holly (I. opaca), only one scientific name can be used for each species and no two species can share the same scientific name. Believe it or not, this eliminates confusion!

As one of winterberry's common names implies, it is a more northern species (as compared to others of the Ilex genus) although it can be found as far south as Georgia and Missouri. Its range extends northward to Minnesota and Newfoundland.

In spite of winterberry's many aliases, which often implies many uses, winterberry only has a few. The Iroquois used bark extracts as an astringent, poultice and antiseptic. A tea can be made from the leaves, but the berries are said to be poisonous to humans. As winterberry is an obligatory wetland plant (OBPL), it makes a nice landscaping shrub in areas where soil moisture is high. However, please don't collect any plants from Volo Bog S.N.A. or other state lands (as it's illegal), but look for Ilex verticillata from various Midwestern nurseries that specialize in native plants. Or better yet, just come visit this fall and watch the show!

All the photos are from October and November, 2025, by Julia Denne.🌿