Alder-leaved Buckthorn
Michigan has a native Buckthorn, Alder-leaved Buckthorn (Rhamnus alnifolia). It normally grows in fens and is seldom found in dry habitats. It is similar to the invasive Common Buckthorn (R. cathartica) but the two species are easy to tell apart.
Alder-leaved Buckthorn showing stipules and leaf characters
Alder-leaved Buckthorn is normally shorter than 1m [3 feet] tall. Its toothed leaves are strictly alternate with 5 to 9 veins per side and are more pointed at the tips than Common Buckthorn. The leaves have stipules at the base of the petioles; however, they are sometimes missing late in the growing season. The flowers lack petals. The petal-like structures are sepals. Sepals are the covering of flower buds; petals are found inside the bud. There are 5 sepals and 5 stamens on each flower. The flowers, and hence the fruits, are in small groups, less than 3 in a cluster.
Alder-leaved Buckthorn flowers, immature fruit, and ripe fruit
Common Buckthorn can reach the size of a small tree. Its toothed leaves can vary from alternate, to sub-opposite, to opposite, on the same branch. Its flowers are 4-parted with both sepals and petals. Flower and fruit clusters are large, seldom as few as 3in a cluster. The branch tips are normally spine tipped and spines can often be found on the along the main trunk.
Glossy Buckthorn (Frangula alnus) is a wetland invasive species but has non-toothed leaves. Its veins are 6 to 9 per side. It has 5 sepals and 5 petals on each flower. The leaf buds are tan pubescent (covered with dense short hairs).
If you are removing invasive buckthorn you should know this native species. One site in Oakland County was almost destroyed by over-zealous invasive species hunters who did not realize that the invasive Common Buckthorn did not grow into the fen at the bottom of the hill.
Copyright 2016 by Donald Drife
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Here in Bay City, I have buckthorns trees growing in my yard. In the city. I have also seen them growing along the rail trail in the stretch between Youngs Ditch and M15. This area is a very wet swampy area with a corn field on the other side of the trees (about 10 meters across). These plants all are small trees, with trunks that are 4 or 5 inches in diameter. Are these the invasive species?
Wendy,
I can’t be sure from your description, but if your plants are buckthorn they sound more like the invasive species than the native. There are links to both of the invasive species in the blog post on the native species. You just have to click on the blue text and you will go to the other posts on those species. The post on Common buckthorn is at http://www.michigannatureguy.com/blog/2013/07/23/common-buckthorn-michigan/ and the one on Glossy Buckthorn can be found at http://www.michigannatureguy.com/blog/2015/04/19/glossy-buckthorn-in-michigan/
Check out these other two posts and you should be able to determine what your plants are.