As winter approaches and deciduous trees lose their leaves, the Arboretum clearly sports a new look. In mid-November, browns are the dominant color and pointed skeletal structures are revealed. Some leaves, however, still remain, fighting the chill in the air. In some cases, this is due to a phenomenon known as marcescence. Many trees abandon their leaves as soon as the fall colors come around, to conserve resources during the winter, when water is sparse. Others hold on to their dry, brown leaves throughout the winter. The latter is what characterizes marcescence. There are hypothesized benefits to holding onto leaves, one being that dropping leaves in the late winter can allow for increased spring nutrient absorption from the decomposed leaves. Another idea is that keeping old leaves can help protect spring buds from browsing deer. In the Arboretum, marcescence can be seen in oak species (Quercus), though often, as trees age, the characteristic is abandoned (for more: https://shorturl.at/MZ0UZ).

While wandering through the Arboretum, one may additionally notice bushes flaunting bright green leaves. It is safe to assume that species that have managed to hold onto their green are not native to this region. Two of the most problematic nonnative species are buckthorn (Rhamnus cathartica) and bush honeysuckle (Lonicera tatarica, Lonicera morrowii). Buckthorn is of Eurasian origin — so is honeysuckle — and was introduced to the Upper Midwest as a hedge plant in the 1800’s. Honeysuckle was introduced, ironically, as erosion control, when in reality it can increase erosion by shading out ground cover. Both species outcompete native flora and degrade habitat. Their leaves remain green due to environmental differences in their native habitats. They can photosynthesize for longer, giving them an advantage over native species. The fall can provide a unique opportunity to manage invasive species. Some removal strategies for buckthorn and honeysuckle practiced in the Arboretum include hand tools, chainsaws, herbicides and frequent controlled burns (more info here https://shorturl.at/1bImh).