Cinnamomum cassia elongated leaves that are long and have a decidedly reddish colour when young. Chinese cassia is a close relative to Ceylon cinnamon ("C. verum"), Saigon cinnamon ("C. loureiroi"), also known as "Vietnamese cinnamon", Indonesian cinnamon ("C. burmannii"), also called "korintje", and Malabar cinnamon ("C. citriodorum") from Sri Lanka. In all five species, the dried bark is used as a spice. Chinese cassia's flavour is less delicate than that of Ceylon cinnamon. Its bark is thicker, more difficult to crush, and has a rougher texture than that of Ceylon cinnamon. Most of the spice sold as cinnamon in the United States,
Cassia crossbill a small area and on a singular food source is due to the lack of squirrels, the usual primary seed dispersal of the lodgepole pine. As a result, serotinous cones are especially abundant in this region, which allows cones with seeds to accumulate in high quantities that will last for decades. This has led to a coevolutionary arms race between the crossbill and lodgepole pine, as the Cassia crossbill is the primary selective agent. In result, the lodgepole pine are creating cones with thick-scaled cones, whilst the crossbills have evolved deeper bills to counter this. The seeds of younger serotinous