Callistemon citrinus, also known as Crimson Bottlebrush is a shrub in the family Myrtaceae. It is native to south-eastern Australia.

Description

Callistemon citrinus grows to between 1 and 3 metres in height and has leaves which are 3 to 7 cm long and 5 to 8 mm wide. The veins of the leaves are clearly visible on both sides.^[1] The flower spikes are 6 to 10 cm in length and about 4 to 7 cm in diameter. These appear in November and December (late spring to early summer) in the species native range.^[2] The stamens are red, purplish-red or lilac with dark-coloured anthers.^[1] The seed capsules are woody, cup-shaped and about 7mm wide and appear in clusters along the stems.^[2]

Taxonomy

The species was formally described by English botanist William Curtis in the The Botanical Magazine in 1794, based on a flowering plant growing at Lord Cremorne's estate.^[3][4] This particular plant had been grown from a root sent from Botany Bay.^[4] Curtis classified this species within the genus Metrosideros, which had been erected by English botanist Joseph Banks in 1788.^[5] Curtis gave it the name Metrosideros citrina, noting that the leaves "when bruised give forth an agreeable fragrance".^[4] The species was transferred to the genus Callistemon in 1913 by botanist Homer Collar Skeels in the United States Department of Agriculture, Bureau of Plant Industry Bulletin.^[6] The species was known by the illegitimate name Callistemon lanceolatus for many years.^[7]

Distribution and habitat

It is native to the states of Queensland, New South Wales and Victoria in Australia, occurring in the vicinity of rocky streams and near-coastal swamps.^[1] In Victoria, the species occurs in the east of the state in association with tree species including Eucalyptus globoidea and E. consideniana.^[2]

Ecology

Birds have been observed using the species as a source of food. Those seeking nectar from the flowers include Eastern Spinebills, New Holland Honeyeaters, Noisy Miners, Red Wattlebirds and Silvereyes, while Crimson Rosellas eat the seeds.^[8]

Cultivation

Plants growing in a glasshouse

Callistemon citrinus had become established in cultivation in England by 1794 when flowering plants that were more than five years old had been observed at both Kew Gardens and Syon House and younger plants had become available in nurseries.^[4]

C. citrinus can be grown outdoors in warm, dry climates, with a minimum temperature of 7 °C (45 °F). It thrives in well-drained soils rich in organic matter, and direct sunlight. Indoors, it will grow well in normal room temperatures and low humidity. However, it requires more sunlight than most houseplants. Plants will benefit from being moved outdoors to a sunny area in summer.^[9] New plants can be grown by taking stem tip cuttings in spring or early summer. Cuttings can be rooted in a mix of peat moss and coarse sand, kept moist. Plants can also be sown by seed in spring.^[9]

Cultivars

Numerous cultivars have been selected including:^[10]

• 'Demesne Rowena' - A cross between 'Splendens' and 'White Anzac' growing to 1.5 x 1.5 metres. The flowers are red upon opening, fading to deep pink.^[11]
• 'Firebrand', a seedling of uncertain origin first planted at Austraflora Nursery in 1973. Plants are about 60 cm high and 2.5 metres wide and have deep crimson-pink flowers.^[11]
• 'Splendens', a form with a compact and rounded habit, growing to about 2 metres high and wide. It is sold under the trade name "Endeavour".^[11]
• 'White Anzac', a low, spreading white-flowering form selected from a natural population in New South Wales.^[12]
• Little John, aka Dwarf Bottlebrush. grows to 3' tall, 5' wide. Red flowers, blue-green leaves covering the branches. Drought-tolerant.^[13] (also classified as C.viminalis)

Uses

The herbicide Mesotrione was developed as a synthetic analogue of leptospermone, a natural herbicide produced by the roots of Callistemon citrinus.^[14]

References