Arceuthobium pusillum easily qualifies as our smallest shrub. Most plants are less than 3 cm tall. It is a parasite on the branches of trees, mostly Picea mariana (black spruce) in our area, where it may cause the conspicuous growth deformity known as "witch's broom". This species is dioecious, meaning that each flower is either male or female and each individual plant bears either male or female flowers, but not both. The leaves are reduced to tiny scale-like structures. Although this species is parasitic, it does produce a little chlorophyll and it does photosynthesize, although not enough to sustain itself without a host.