While birding along the Cape Cod Canal on Saturday, I noticed a fairly large clearing filled with green, densely branched low-growing shrubs. Upon closer inspection, the stems were strongly angled with alternately arranged pinkish-brown buds. Even without leaves or flowers, it did not take long to identify this shrub as Scotch broom (Cytisus scoparius). This non-native shrub flourishes in full sunlight in dry, sandy soils, making it no surprise that it was so abundant in this Cape Cod clearing.

Scotch broom is native to northern Africa and parts of Europe. It was first introduced to the east coast of the U.S. in the 1800s as an ornamental due to the showy, bright yellow, pea-like flowers it produces in the spring. It was also widely planted for erosion control along highways in the 1900s. Since its early introduction, it has become rather invasive. Several characteristics contribute to its success: the green photosynthetic tissue in its stems allows it to grow and capture energy throughout the year, even when it no longer has leaves; as a member of the legume family, it is a nitrogen-fixing plant, allowing it to establish and survive in nutrient-poor soils; and it produces abundant seeds that remain viable in the soil for many years. If all of this wasn’t enough to set it up for success in a new country, Scotch broom is also slightly toxic and unpalatable to livestock, limiting the amount of damage it sustains due to herbivory. 

Final fun fact: The name scotch broom comes from the fact that a dense mass of the slim stems was once cut and made into brooms.