German Ivy

''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''. It is known as Cape ivy in some parts of the world (US) and German ivy in others (Britain, Ireland). Other names include parlor ivy and Italian ivy. 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.''Delairea odorata''
PlantFileonline

Description

''Delairea odorata'' is a fast-growing vine that climbs up trees and will reach heights of . 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 than thick, and glabrous. The glossy and semi-succulent leaves, which are long and 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.''Delairea odorata''
Environmental Weeds of Australia

The plant's stems and leaves die off between late summer and early autumn, but are superseded by new shoots that employ the old stems as climbing support.

Inflorescence

Its sweet-scented discoid 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 ( long). Flower-heads ( across and 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.

The seeds (or achenes) are approximately long and are reddish-brown in colour as they age. They feature a pappus of silky white hairs that is long. 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 .

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 . 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. It is found in wetter temperate regions, but it may still be found in cooler subtropical environments, although it is frost tender. It prefers partial shade, but can withstand heavy shade. In more damp areas, it can prosper in full sun. Despite its invasive nature, the plant is grown as an ornamental houseplant for its foliage.

Ecological impact

''Delairea odorata'' has become an invasive species in coastal California starting in 1892, CABI ISCbr>20143118470
Hawaii, coastal 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.

The vine reaches maturity in 2 years and it can produce over 30,000 seeds annually. In Hawaii an introduced species of moth (''Galtara extensa'') for the biological control of ''Senecio madagascariensis'' both originally from Madagascar proved to feed also on ''D.odorata''.

''D.odorata'' is the host of ', a species nova introduced by Groenewald ''et al.'', 2013.

It is presently known only from the same South African native range of the host. Due to the pathogen's effects especially its leaf spot disease they advocate ''C.delaireae'' as a potential biocontrol of the vine in its invasive ranges.

Another organism from its native range, the moth '' Digitivalva delaireae'', also can be used as a biocontrol.

Mehelis ''et al.'', 2015 test its food preferences and find it is very selective for ''D.odorata''. Because it avoids any vulnerable native plants in California and Oregon it is a good choice specifically to control the infestations there.

There is a report in California by a man who claimed that after walking through a clump of Cape ivy in his ranch, whilst in full blooms, he became lightheaded, fainted and had a seizure. Before this, he had coughing fits while trying to eradicate the plant, which was not in flower at the time.

Cultivation

Germany ivy is grown as a vine or groundcover, where it can vigorously climb up posts, hedges, trees and shrubs, fences, banks, and walls.Delairea odorata
Forest Starr, Kim Starr, and Lloyd Loope. United States Geological Survey--Biological Resources Division. Haleakala Field Station, Maui, Hawai'i. January, 2003.Retrieved 31 October 2022. The plant is cultivated in landscaping for its ivy-like leaves and scented flowers in bright light or light shade away from abundant sunlight. Propagation is done by cuttings as its stems root readily both in water and soil, without the need for a rooting hormone. In addition to being drought-tolerant, it cannot withstand soggy soils. When overwatered, its leaves turn brown and have curled edges. Conversely, underwatering will cause its leaves to fall. Pruning is encouraged for a bushy and compact growth. Pests include mealy bugs and aphids, and diseases include leaf spot and root rot.

History

The plant was introduced to the United States in the 19th century as a Victorian era-style houseplant. In the 1850s, in Geelong, the plant was described in the Geelong Advertiser, "the great stumps, over which the little boys played leap-frogs in the Sydney Morning Herald mention a Cape Ivy observed on the dunes at Newcastle, New South Wales and Gulaga. In 1909, it was introduced as an ornamental to Kailua-Kona, Hawaii. Neal (1965) describes the plant as, "both a weed and an ornamental."

Related species

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 ''D. odorata'' historically, and these species have been confused regularly despite the visual differences. A feature that distinguishes it from ''S. angulatus'' are the small ear-shaped appendages at the base of the stalks of the leaves, its intertwining habit, and its flowers which do not have obvious 'petals', whereas ''S. angulatus'' and '' S. tamoides'' have daisy-like flowers. Moreover, ''S. angulatus'' is more of a scrambler, whereas ''S. tamoides'' and Delairea grow more like true vines.climbing groundsel
Brisbane City Council Weed Identification Tool Atlas of Living Australia has also misapplied ''S. tamoides'' for its ''D. odorata'' observations in Australia.

Gallery

File:Starr-090519-8088-Delairea odorata-flowers and leaves-Kula-Maui (24325129764).jpg, alt=In a shrubland
File:Delairea.jpg, alt=Trailing on branches
File:Senecio mikanioides (delairea odorata).jpg, alt=Flowers detail
File:Starr 070621-7438 Delairea odorata.jpg, Hawaii, alt=Draping habit in Hawaii
File:Starr 001218-0079 Delairea odorata.jpg, alt=Climbing over trees
File:Starr 070308-5481 Delairea odorata.jpg, Hawaii, alt=Covering bushland in Hawaii
File:Starr 070308-5485 Delairea odorata.jpg, Monarch butterfly, alt=Flowers pollinated by monarch butterfly

References

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{{Taxonbar, from1=Q2702202, from2=Q16029211

Senecioneae
Monotypic Asteraceae genera
Flora of South Africa
Vines
Groundcovers
Creepers of South Africa
Garden plants of Southern Africa
Invasive plant species in the United States