Bottlebrush trees (Callistemon) are part of the Myrtaceae or myrtle family, related to familiar species like guava (Psidium) and clove (Syzygium aromaticum). There are about 20 species of bottlebrush shrubs and small trees, all of which are native to Australia. The plants are evergreen, with simple, aromatic alternate leaves. The most readily identifiable feature is the showy flower spikes. The flower petals are yellow or red and tiny, but the elongated, red flower stamens give the plant its nickname and distinctive appearance.
Bottlebrushes are important as landscape subjects in warm climates. They can withstand sandy soil and at least one species, Callistemon citrinus is somewhat salt tolerant, making the plants useful for coastal locations. Weeping bottlebrush or Callistemon viminalis takes readily to clipping and can be used effectively as a hedging or screening plant. This species can also be substituted for weeping willow at the edges of ponds or water features. Bottlebrush trees do not cause much litter and are well-suited to use around high traffic areas. Bottlebrushes also attract hummingbirds.
Among the more popular Callistemon species are Callistemon citrinus or crimson bottlebrush, which has citrus-scented foliage; Callistemon rigidus, the erect bottlebrush; Callistemon salignus; and Callistemon viminalis, the weeping bottlebrush. Cultivated varieties and hybrids of some species are also available. According to Dr. Michael Dirr, many of the Callistemon species are virtually identical to each other as young plants, making definitive identification difficult.
At the end of the 19th century, the hardwood of Callistemon citrinus was harvested for building purposes. Callistemon citrinus was used for shipbuilding and wagon or cart wheels as well as mallets. Timber from Callistemon salignus was close-grained and survived well when buried, making it useful for posts and other applications that required portions of the wood to be installed in the soil.
Bottlebrushes were first discovered on pioneering Australian expeditions in the late 18th century. Renowned British botanist Joseph Banks collected specimens of Callistemon citrinus--the first bottlebrush discovered--in 1770, on the East Coast of Australia. Other species were discovered over the course of the next 50 years and sent back to Europe. Period illustrations show that Callistemon speciosus was grown in the Empress Josephine's fabled garden at Malmaison. Because foreign plants were of great interest to the British public, slabs of Callistemon salignus were exhibited at the London International Exhibition of 1862.
Bottlebrushes can be cultivated in warm winter areas like Florida and the Pacific Coast of California. The primary requirements are warm temperatures, adequate moisture and plenty of sun. Callistemon can be grown from seed, and the seed does not need any pre-treatment. If the young plants are purchased in containers, they should be transplanted and watered regularly until they are established. During the growing season, bottlebrushes should be fertilized regularly. In cold winter climates, potted specimens can be brought indoors and overwintered in cool greenhouses or cool household spaces.