Melaleuca citrina

Melaleuca citrina, commonly known as common red, crimson or lemon bottlebrush,[2] is a plant in the myrtle family, Myrtaceae and is endemic to New South Wales and Victoria in Australia. (Some Australian state herbaria continue to use the name Callistemon citrinus.[3] Callistemon lanceolatus is an older name.)[4] It is a hardy and adaptable species, common in its natural habitat. It is widely cultivated, not only in Australia, often as a species of Callistemon. It was one of the first Australian plants to be grown outside the country, having been taken to England in 1770 by Joseph Banks. Its showy red flower spikes, present over most of the year in an ideal situation, account for its popularity.

Crimson bottlebrush
Melaleuca citrina flowers, fruit and foliage
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Myrtales
Family:	Myrtaceae
Genus:	Melaleuca
Species:	M. citrina
Binomial name
Melaleuca citrina (Curtis) Dum.Cours.
Synonyms[1]
Metrosideros citrina Curtis Callistemon lanceolatus (Sm.) Sweet Callistemon citrinus (Curtis) Skeels

Description

Melaleuca citrina is a shrub growing to 5 m (20 ft) tall but more usually in the range 1–3 m (3–10 ft) high and wide. It has hard, fibrous or papery bark and its young growth is usually covered with soft, silky hairs. Its leaves are arranged alternately and are 26–99 mm (1–4 in) long, 4–25 mm (0.2–1 in) wide, hard, flat, narrow egg-shaped with the narrower end near the base and with a pointed but not sharp end. There are between 7 and 26 branching veins clearly visible on both sides of the leaves and a large number of distinct oil glands visible on both surfaces of the leaves.[1][5]

The flowers are red and arranged in spikes on the ends of branches that continue to grow after flowering and sometimes also in the upper leaf axils. The spikes are up to 45–70 mm (2–3 in) in diameter and 60–100 mm (2–4 in) long with up to 80 individual flowers. The petals are 3.9–5.8 mm (0.15–0.23 in) long and fall off as the flower ages. There are 30 to 45 stamens in each flower, with their "stalks" (the filaments) red and "tips" (the anthers) purple. Flowering occurs in most months of the year but mainly in November and December. Flowering is followed by fruit that are woody, cup-shaped capsules, 4.4–7 mm (0.2–0.3 in) long and about 7 mm (0.3 in) wide in cylindrical clusters along the stem. The fruiting capsules remain unopened until the plant, or the part bearing them dies.[1][5]

Taxonomy and naming

Melaleuca citrina was first formally described in 1802 by the French botanist Georges Louis Marie Dumont de Courset in Le Botaniste Cultivateur.[6] The species had previously been known as Metrosideros citrina, in turn named by William Curtis in the Botanical Magazine in 1794, based on a flowering plant growing at Lord Cremorne's estate. That plant had grown from a root collected in 1770 at Botany Bay by Joseph Banks during the first voyage of James Cook to Australia. Curtis noted that the leaves "when bruised give forth an agreeable fragrance."[7][8] The specific epithet (citrina) alludes to the similarity of the aromatic property of leaves of this species and those of citrus plants.[1]

Callistemon citrinus is regarded as a synonym of Melaleuca citrina by the Royal Botanic Gardens, Kew.[9]

Distribution and habitat

Melaleuca citrina occurs in near coastal areas of New South Wales, including the Blue Mountains and extends as far west as the Central Western Slopes.[5] It also occurs in the east coast areas of Victoria[1] and grows in swamps and along creeks and rivers.[5]

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.[10]

Uses

Agriculture

The herbicide Mesotrione was developed as a synthetic analogue of leptospermone, a natural herbicide produced by the roots of Callistemon citrinus.[11]

Horticulture

M. citrina, as 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.[7] It is widely cultivated, often as Callistemon citrinus and sometimes as Callistemon lanceolatus. It is easily propagated from seed or cuttings and grows in most soils, preferring a sunny location. It is frost hardy and responds well to watering and the application of fertiliser but is tolerant of drought and frost.[12][13][14]

A number of cultivars have been developed (as cultivars of Callistemon citrinus) including:[15]

• '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.[16]
• '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.[17]
• 'Splendens', a form with a compact and rounded habit, growing to about 2 metres high and wide. In Australia it is sold under the trade name "Endeavour".[18] In the UK it has received the Royal Horticultural Society's Award of Garden Merit.[19]
• 'White Anzac', a low, spreading white-flowering form selected from a natural population in New South Wales.[20]

References

1. Brophy, Joseph J.; Craven, Lyndley A.; Doran, John C. (2013). Melaleucas : their botany, essential oils and uses. Canberra: Australian Centre for International Agricultural Research. p. 119. ISBN 9781922137517.
2. "Callistemon citrinus". APNI. Retrieved 30 August 2015.
3. Udovicic, Frank; Spencer, Roger (2012). "New combinations in Callistemon (Myrtaceae)" (PDF). Muelleria. 30 (1): 23–25. Retrieved 11 June 2015.
4. "Callistemon citrinus". Australian Native Plants Society Australia. Retrieved 20 July 2015.
5. "Callistemon citrinus". Royal Botanic Garden Sydney: PlantNet. Retrieved 12 June 2015.
6. "Melaleuca citrina". APNI. Retrieved 12 June 2015.
7. Curtis, William (1794). The Botanical Magazine (Volume 8) (1 ed.). London. p. 260. Retrieved 12 June 2015.
8. "Metrosideros citrina". APNI. Retrieved 12 June 2015.
9. "Callistemon citrinus". World Checklist of Selected Plant Families (WCSP). Royal Botanic Gardens, Kew.
10. Lepschi, B.J. (1993). "Food of some birds in eastern New South Wales"Additions to Barker & Vestjens" (PDF). Emu. 93 (3): 195–199. doi:10.1071/MU9930195.
11. Cornes, Derek. "Fourth World Congress on Allelopathy". The Regional Institute Ltd. Retrieved 18 July 2015.
12. "Callistemon citrinus". Plants for a Future. Retrieved 12 June 2015.
13. "Callistemon citrinus". Australian Native Plants Society (Australia). Retrieved 12 June 2015.
14. "Callistemon citrinus". Australian National Botanic Garden. Retrieved 12 June 2015.
15. "List of Registered Cultivars derived from Australian native flora". Australian Cultivar Registration Authority Inc. Retrieved 18 July 2015.
16. "Callistemon 'Demesne Rowena'". Australian Cultivar Registration Authority. Retrieved 18 July 2015.
17. "Callistemon 'Firebrand'". Australian Cultivar Registration Authority. Retrieved 18 July 2015.
18. "Callistemon 'Splendens'". Australian Cultivar Registration Authority. Retrieved 18 July 2015.
19. "Callistemon citrinus 'Splendens'". www.rhs.org. Royal Horticultural Society. Retrieved 12 April 2020.
20. "Callistemon 'White Anzac'". Australian Cultivar Registration Authority. Retrieved 18 July 2015.