Common Buckthorn is a highly invasive species with simple, alternate leaves and black or red berry- like drupes. It has a woody spine at the end of each twig, hence the name. It spreads so well because it is a super efficient grower that doesn’t need much sunlight and is very fertile. The seeds are very hardy and grow and spread in a variety of conditions. And animals do not like to eat the fruit, which may even make them sick.
Not only is buckthorn highly invasive- you see it all over the place - but it is also a host for the soybean aphid AND an oat fungus. Honestly, it doesn’t have much to recommend it! The berries do, however, contain a yellow dye and make a beautiful sap-green ink.