Invasive Species Guide
This page will serve as a brief introduction to identifying several of the more common invasive species that may be found in the Green Bay area. For further information please refer to the UWGB Herbarium Website, or a botany book. Species are sorted by scientific name. If you would like to learn more about the subject, I highly recommend Gary Fewless' Field Botany class.
Lonicera X bella
Common Name: Showy Bush Honeysuckle
Once you've seen Lonicera X Bella several times in the field, you will have no problem recognizing it. The buds are opposite, and very distinctive. In my opinion the shrub always has a very dried out appearance that makes it stand out. In the picture you can see that I have shaved a bit of bark off a twig to expose the pith. All non-native Lonicera's have hollow piths (as shown in the picture), which makes them extremely easy to identify if you have a knife.
Rhamnus cathartica
Common Name: European buckthorn
Rhamnus cathartica is another invasive that is easy to identify with a little experience. The buds are a dark black that you will often be able to spot from some distance. The branches of this tree are also tipped with a thorn that is easily recognizable. Be aware that both opposite and alternate leaves can exist on the same tree, so the leaf/bud spacing is not a good characteristic to study. Rhamnus species will often keep their leaves well into winter, and will stay green long after other trees have turned.
I found this Fraxinus (left) growing next to a Rhamnus cathartica (right) in Baird' Creek. Note that some species of Fraxinus may have dark buds, but the buds are a very different shape. If you are unsure, check for the presence of thorns, which are not found on Fraxinus species.
© 2008 Andrew Christ.