Rainbow eucalyptus
Eucalyptus deglupta bark on young trees in Hawaii
Conservation status
Vulnerable  (IUCN 3.1)[1]
Scientific classification
Kingdom:	Plantae
Clade:	Tracheophytes
Clade:	Angiosperms
Clade:	Eudicots
Clade:	Rosids
Order:	Myrtales
Family:	Myrtaceae
Genus:	Eucalyptus
Species:	E. deglupta
Binomial name
Eucalyptus deglupta Blume[2]
Synonyms[2]
Eucalyptus binacag (Elmer) Elmer Eucalyptus multiflora Rich. ex A.Gray nom. illeg. Eucalyptus naudiniana F.Muell. Eucalyptus sarassa Blume Eucalyptus schlechteri Diels Eucalyptus versicolor Blume Eugenia binacag Elmer

Eucalyptus deglupta is a species of tall tree, commonly known as the rainbow eucalyptus,^[3] Mindanao gum, or rainbow gum^[4] that is native to the Philippines, Indonesia, and Papua New Guinea. It is the only Eucalyptus species that usually lives in rainforest, with a natural range that extends into the Northern Hemisphere. It is characterized by multi-colored bark.

Description

Flowers

Fruit

Eucalyptus deglupta is a fast-growing tree that typically reaches a height of 60–75 m (197–246 ft) with the trunk up to 240 cm (94 in) in diameter and with buttresses up to 4 m (13 ft) high. It has smooth, orange-tinted bark that sheds in strips, revealing streaks of pale green, red, orange, grey, and purplish brown. The branchlets are roughly square in cross section, often with narrow wings on the corners. The leaves are arranged in opposite pairs, mostly 75–150 mm (3–6 in) long and 50–75 mm (2–3 in) wide on a short petiole. The flower buds are arranged in a branching inflorescence in leaf axils, or on the end of branchlets, each branch with groups of seven buds, the individual buds on a pedicel about 5 mm (3⁄16 in) long. Mature buds are pale green or cream-colored, roughly spherical in shape and 2–5 mm (1⁄16–3⁄16 in) in diameter with a hemispherical operculum with a small point on the top. Flowering time depends on location, and the stamens that give the flowers their colour are white and pale yellow. The fruit is a woody, brown, hemispherical capsule about 3–5 mm (1⁄8–3⁄16 in) long and wide, with three or four valves extending beyond the rim of the fruit. Each cell of the fruit contains between three and twelve minute brown seeds, each with a small wing.^[5][6]

Taxonomy and naming

Eucalyptus deglupta was first formally described in 1850 by Carl Ludwig Blume who published the description in his book Museum Botanicum Lugduno-Batavum sive stirpium Exoticarum, Novarum vel Minus Cognitarum ex Vivis aut Siccis Brevis Expositio et Descriptio from material collected in mountain forests in the Celebes.^[2][7] The specific epithet (deglupta) is a Latin word meaning "peeled off, husked or shelled".^[8]

In 1914, Adolph Daniel Edward Elmer described Eugenia binacag in Leaflets of Philippine Botany, the specific epithet binacag a local name for the tree,^[9] but in 1915 changed the name to Eucalyptus binacag.^[10] However, the species had already been named E. deglupta by Blume in 1850 and E. binacag is now regarded as a synonym.^[2]

In 1854, Asa Gray described Eucalyptus multiflora in United States Exploring Expedition - Botany, Phanerogamia from an unpublished description by Louis Claude Richard,^[11][12] but is a nomen illegitimum because the name was already in use for a different species (Eucalyptus multiflora Poir.) now known as Eucalyptus robusta.^[13] Eucalyptus multiflora is also a synonym of E. deglupta.^[2]

Eucalyptus sarassa and E. versicolor, first described in 1850 by Blume in his book Museum botanicum Lugduno-Batavum,^[14] and E. schlechteri first described by Ludwig Diels in Adolf Engler's book Botanische Jahrbücher für Systematik, Pflanzengeschichte und Pflanzengeographie^[15] are also considered to be synonyms of E. deglupta by Plants of the World Online.^[2]

Distribution and habitat

The rainbow eucalyptus grows in lowland and lower montane rainforest from sea level to altitudes of up to 1,800 m (5,900 ft). It is native to Indonesia, Papua New Guinea, and the Philippines, but has been widely planted in many other countries.^[2]

The populations of this species are severely fragmented in the wild and the overall population is decreasing. Over the last 210 years it is estimated that there has been a 30% decline of the overall population. The International Union for the Conservation of Nature listed E. deglupta as a vulnerable species in 2019.^[1]

Uses

Use in horticulture

Bark of E. deglupta in a grove of trees on Maui, Hawaii

E. deglupta are commonly planted as ornamental trees in frost-free climates such as Hawaii, Southern California, Texas and Florida.^[18] It is planted in at least three locations in coastal Los Angeles County, including Santa Monica and San Marino at the Huntington Botanical Garden. These trees were still growing, but relatively young at approximately 30–40 years in 1988, at the UCLA Botanic Garden and as a LA City street tree.^[19]

If grown from seed, the temperature should be around 68–72 °F (20–22 °C).^[20] Plants can be grown from cuttings of trees younger than 5 years old. Once a tree reaches 5 years of age, root inhibition prevents the generation of roots from cuttings.^[21] It thrives in rich medium-to-wet soil in full sun and is intolerant of frost.^[22] In botanical gardens such as Fairchild Tropical Botanic Garden in Florida, the tree does show the intense color range as seen in the tree's normal range.^[23][24]

References

Wikimedia Commons has media related to Eucalyptus deglupta.