Delairea

Delairea is a plant genus within the family Asteraceae that is native to South Africa. Classified within the tribe Senecioneae, it contains only one species, Delairea odorata, which was previously included in the genus Senecio as Senecio mikanioides.[4] It is known as Cape ivy in some parts of the world (US) and German ivy[5] in others (Britain, Ireland). Its multi-lobed leaves somewhat resemble those of the unrelated English ivy. Originally used as an ornamental plant on trellises and as groundcover, it is now rarely cultivated because of its invasiveness, in addition to being a weed.[6]

Delairea
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Subfamily: Asteroideae
Tribe: Senecioneae
Genus: Delairea
Lem.[1]
Species:
D. odorata
Binomial name
Delairea odorata
Synonyms[3]
  • Delairea scandens Lem.
  • Senecio mikanioides Otto ex Walp.
  • Senecio scandens Juss. ex DC.

Description
Leaf closeup
Yellow blooms

Delairea odorata is a vine that climbs up trees and will reach heights of 2–4 m (7–13 ft).[6] Though it can also form mats. The plant emits a distinguishing odor when crushed and it also occurs during flowering, hence its species name "odorata" (which means 'fragrant').

Its stems are usually purplish when young and fragile, where they turn green and somewhat succulent. They finally become creamy-brown and slightly woody as they age. They are rounded, normally less then 10 mm thick, and glabrous. The glossy and semi-succulent leaves, which are 3-10 cm long and 3-8 cm wide, are borne on stalks and are alternately arranged along the stems, where they feature 3-10 small lobes or toothed margins. The upper leaf surfaces are light green, but usually somewhat purple-hinted, while the undersurface are somewhat silvery.[7]

The plant's stems and leaves die off between late summer and early autumn, but are superseded by new shoots that employ the old stems as climbing support.[8]

Inflorescence

Its sweet-scented[9] flowers are yellow, which lack the petal-like ray florets found in typical daisies. They have tiny tubular florets surrounded by a row (i.e. involucre) of 8-10 small green bracts (3-5 mm long). Flower-heads (2-7 mm across and 2-5 mm long) are supported in compact clusters at the end of the branches (terminal corymbs), with every cluster comprising about 15-50 flower-heads. Flowering occurs mostly during winter to early spring.[7]

The seeds (or achenes) are approximately 2 mm long and are reddish-brown in colour as they age. They feature a pappus of silky white hairs that is 5-6 mm long.[7] Most of its seed in North America and possibly elsewhere are unviable, which may be the deficiency of effective pollinators. However, the plant can rather promptly reproduce from stem fragments, stolons, or rhizomes as small as 2.5 cm.[10]

Habitat and distribution

The plant is actually uncommon in its native country of South Africa, where it was originally found in the Drakensberg Mountains, on forest edges, at elevations above 1500 m. Its occurrence at the more coastal areas (some of which are arid) in South Africa is probably more recent. In California, it is generally found in the fog belt on the coast, with a few specimens found inland, particularly in riparian sites that feature permanent moisture.[10] It is found in wetter temperate regions, but it may still be found in cooler subtropical environments. It prefers partial shade, but can withstand heavy shade, and in more damp areas, it can prosper in full sun, though it is frost tender. Despite its invasive nature, the plant is grown as an ornamental houseplant for its foliage.[10]

Ecological impact

Delairea odorata has become an invasive species in parts of California, Hawaii, Oregon, New Zealand and southern Australia (particularly in Victoria). The plant will cover shrubs and trees, inhibiting growth and will also cover ground intensively over a wide area, thereby preventing seeds from germinating or growing. It is also toxic to animals who eat it and to fish where it trails into waterways.[11] In the 1850s, in Geelong, the plant was described in the Geelong Advertiser, "the great stumps, over which the little boys played leap-frog, are either gone or covered with the Cape ivy". Furthermore, 1856 and 1864 columns in the Sydney Morning Herald mentions Cape Ivy on the dunes at Newcastle, New South Wales and Gulaga.[12]

The vine reaches maturity in 2 years and it can produce over 30,000 seeds annually.[6] In Hawaii an introduced species of moth (Galtara extensa) for the biological control of Senecio madagascariensis proved to feed also on Delairea odorata.[13]

The name Cape ivy is also used ambiguously for Senecio angulatus, a different but related creeper. S. angulatus has been incorrectly listed as a synonym to Delairea odorata historically, and these species have been confused regularly despite the visual differences. Senecio tamoides is another similar looking plant in the same tribe, which is often mistaken for the two aforementioned species.

A feature that distinguishes it from Senecio angulatus are the small ear-shaped appendages at the base of the stalks of the leaves and its flowers which do not have obvious 'petals', whereas S. angulatus and S. tamoides have daisy-like flowers.

  • In a shrubland
  • Trailing on branches
  • Flowers detail
  • Draping habit in Hawaii
  • Climbing over trees
  • Covering bushland in Hawaii
  • Flowers pollinated by monarch butterfly
  • Cultivated as a pot plant in India

References
  1. Natural Resources Conservation Service (NRCS). "PLANTS Profile, Delairea Lem". The PLANTS Database. United States Department of Agriculture. Retrieved 2008-03-31.
  2. Integrated Taxonomic Information System Organization (ITIS) (1999). "Delairea Lem". Integrated Taxonomic Information System on-line database. Retrieved 2008-03-31.
  3. The Plant List, Delairea odorata Lem.
  4. Eda, Sayaka (1999). "The Biogeography of Cape Ivy (Delairea odorata)". Archived from the original on 2007-05-13. Retrieved 2007-05-20.
  5. BSBI List 2007 (xls). Botanical Society of Britain and Ireland. Archived from the original (xls) on 2015-06-26. Retrieved 2014-10-17.
  6. Delairea odorata PlantFileonline
  7. Delairea odorata Environmental Weeds of Australia
  8. DiTomaso, J. M., Kyser, G. B., Oneto, S. R., Wilson, R. G., Orloff, S. B., Anderson, L. W., ... & Mann, J. J. (2013). Weed Report: Delairea odorata Cape-ivy In: Weed control in natural areas in the western United States. Weed Research and Information Center, University of California, 544.
  9. Cape Ivy Collated by HerbiGuide
  10. Delairea odorata (Cape ivy) Centre for Agriculture and Bioscience International
  11. Delairea odorata (Senecio mikaniodes) (Cape Ivy, German Ivy) (27.Jun.2015)
  12. Cape Ivy (Delairea odorata) WEEDS OF MELBOURNE. July 4, 2019.
  13. North Hawaii News: Miracle moth from Madagascar Archived 2014-10-11 at the Wayback Machine (7.Oct.2014)

Bibliography
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