I think my most common summer phrase is “berry season is the best season”. I’ve been thoroughly enjoying wild-picked blueberries, huckleberries, red and black raspberries, and wineberries, as well as  the blackberries that are just now starting to ripen (I picked my first ripe one this morning). Now that my eyes have a “berry” search image, there’s one shrub I’m noticing everywhere: glossy buckthorn (Frangula alnus), which grows as a deciduous shrub or a small tree up to 20 feet tall. 

Glossy buckthorn produces a small berry-like fruit, but although these continually catch my eye while I’m out berry picking, these fruits are not edible. Not to humans anyway. Birds, on the other hand, readily consume them, ultimately helping to spread the seeds of this invasive shrub into fields, forests and wetlands, where it crowds out native plants. Originally from Europe, Central Asia, and North Africa, glossy buckthorn is now found throughout much of the northeastern US and southeastern Canada. In fact, this plant is so problematic that the importation, distribution, trade, and sale of glossy buckthorn has been banned in Massachusetts since 2009.

In addition to its high seed production and viability, and its ability to be dispersed over great distances by birds and other berry feeding animals, glossy buckthorn has a number of other traits that allow it to be so successful, and by extension, so invasive. First, glossy buckthorn has an advantageous breeding system: both male and female reproductive parts are produced on the same plant. This means it takes only a single shrub to produce an entire colony. Second, they can also sprout vegetatively from a cut or broken stem, ultimately producing more flowers, fruit, and seeds than the original unbroken stems. Finally, glossy buckthorn can thrive in shady or sunny sites, wetlands or uplands, and has no predators (e.g., caterpillars or other herbivorous animals). The combination of these traits results in a very successful invasive plant. 

Glossy buckthorn has shiny alternate leaves, but no thorns, despite its name. It can be single- or multi-stemmed. The bark is gray to brown with white lenticels. It produces small, greenish-yellow, four-petaled flowers in May and June, which produce pea-sized fruits in the late summer. The fruits begin light colored, then transition to red and then to black as they ripen.