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Old man's beard (Clematis vitalba) is an invasive plant in New Zealand that affects indigenous biodiversity. It is declared an unwanted organism under the Biosecurity Act 1993 which means it cannot be sold, distributed or propagated.

Spread

Old man's beard was introduced into New Zealand as an ornamental plant some time before 1922 and the Department of Conservation and other government organisations now spend millions of dollars on its control.^[1] The seeds are wind-borne on a fluffy boll and can remain on the vine over the winter months. The seeds are most likely to germinate on disturbed ground where the light level is more than 5% of full sunlight. It is more common outside undisturbed forests on forest and stream margins and forest gaps.^[2]

Impact

Old man's beard is a climber that will smother established trees and forms a dense canopy that stops sunlight reaching the soil surface. This affects the health of the existing vegetation and prevents the germination of all other species.^[3]

Control

Various methods are used to control the plant including mechanical removal, herbicides and biological control. Large vines can be cut at ground level and a herbicide gel applied to prevent sprouting. Trailing vines must be removed since they can re-sprout, and small plants can be uprooted.^[4] Biological control agents have been trialled.^[1]

A public service campaign highlighting the threat of old man's beard was carried out by the Department of Conservation in the 1980s using the British naturalist David Bellamy as the spokesperson.^[5]

References

^ ^a ^b Gourlay, A.H.; Wittenberg, R.L.; Hill, A.G.; S.V.Fowler (2000). "The Biological Control Programme against Clematis vitalba in New Zealand". Proceedings of the X International Symposium on Biological Control of Weeds. Montana State University: 709–718.
^ Bungard, R.A.; Daly, G.T.; McNiel, D.L.; Jones, A.V.; Morton, J.D. (1997). "Clematis vitalba in a New Zealand native forest remnant: does seed germination explain distribution?". New Zealand Journal of Botany. 35 (4). The Royal Society of New Zealand: 525–534. Bibcode:1997NZJB...35..525B. doi:10.1080/0028825x.1987.10410176.
^ Ogle, C. C.; G. D. Cock; G. Arnold; N. Mickleson (2000). "Impact of an exotic vine Clematis vitalba (F. Ranunculaceae) and of control measures on plant biodiversity in indigenous forest., Taihape., New Zealand". Austral Ecology. 25 (5): 539–551. doi:10.1111/j.1442-9993.2000.tb00059.x. ISSN 1442-9985.
^ "Old Man's Beard" (PDF). fact sheet. Auckland Regional Council. October 1999. Retrieved 23 July 2010.
^ "NZ On Screen - Old Man's Beard Must Go". 1989. Retrieved 2012-01-20.