The buckthorn is a common shrub or small tree in North America, growing up to 20 feet tall. It is considered an invasive species in many areas, and is the primary host plant for the soybean aphid. Buckthorn spreads rapidly from seed and dominates the understory of forests, crowding out a variety of native plants. Although they provide a minor nectar flow for your bees in May-June, never buy, sell, or plant an invasive species. Encourage the growth of native wildflowers, trees, and shrubs to ensure a varied diet for our pollinators.