Menace of Old man's beard

Waimarino Bulletin, Volume 4, Issue 1, 3 June 1986, Page 7

Menace of Old man's beard

In the second of two articles Martin Nicholls, landscape architect with the Department of Lands and Survey, discusses the threat of Old Man's Beard or Clematis vitalba on native forest.

Old Man's Beard is one of the most serious threats to New Zealand's forests. I have seen this plant for sale in Wanganui garden centres recently. This is frightening in a region where it is a special threat to the bush. I personally cannot see how Old Man's Beard can be regarded as an acceptable garden plant since it grows so rampantly and at the expense of all other plants. The fact that it has been sold in nurseries until recently shows either ignorance or a lack of concern. It is a threat to all forms of indigenous forest - a real botanical curse. Apart from its wind blown seeds, this plant is spread vegetatively in the same way as honeysuckle. It is surprising how easily it spreads and how a moment's carelessness, such as in earthworks operations near indigenous forests, can cause ecological catastrophe. I must stress that other exotic and all native clematis are not a threat to the bush. The commonly grown Clematis montana is an admirable garden plant and its cultivation should continue. When not in flower, however, it can be confused with Clematis Vitalba. Old Man's Beard is easily identified: • coarsely serrated or smooth dull-green leaflets in threes or fives; • stems, square sectioned, ribs prominent while native species have smooth, rounded stems; • flowers, which lack petals, are cream with small sepals,

prominent stamens and stigmatic filaments. Clematis vitalba flowers from summer to autumn, while all native species flower in spring; • it climbs to the tops of the tallest forest trees and cascades down. It can grow very vigorously and densely to the point where it smothers its host vegetation. It then persists as a dense ground cover through which no other vegetation can grow. - In this dramatic way it can convert open rain forest into a pure community of Old Man's Beard. Once it reaches this stage, such as areas near Mangaweka and Taihape, control is virtually impossible or prohibitively expensive. The noxious plants officer for the Waimarino County Council is preparing a register of known infestations of the weed in the district with a view to its being declared a class B noxious plant. If any reader knows of any such infestations it would be helpful if they would report them to the officer. The seed of Old Man's Beard is wind-blown over considerable distances and also is very long-lived, sometimes exceeding 20 years. Seed may also be carried by stock, and horses, on vehicle tyres or soiled parts of vehicles and earth-moving equipment. Earthworks contractors should thoroughly steamclean any plant and equip-

ment before it is moved to an area free of Old Man's Beard. This should not be a problem if it is a normal part of machinery maintenance at the start of new contracts. As well as from seed Old Man's Beard can also grow from cutting fragments or from broken stems. This is especially so along stream sides where fragments can break off and be partially buried by silt. Old Man's Beard's presence along the Mangawhero river, especially near Raetihi, is probably caused this way. Fragments brought in with vehicles and machinery and left after clearing can regrow easily to form large, dense infestations. Those working with Old Man's Beard must pay particular attention to cleanliness. It is important to remember when controlling Old Man's Beard to always ensure that up-stream infestations are cleared first. Similar methods of con-

trol can be used for Old Man's Beard and for the plants described last week: • don't cultivate the plants or purchase them from nurseries; • remove all such plants from home gardens and thoroughly destroy remains; • farmers should look at alternative species for hedge rows and destroy cultivated or wild plants on their properties before infestations become a problem; • form a 'watch-dog' network to seek out and destroy known infestations; • contact the local noxious plants officer for advice on control of exotic plants which are a threat to indigenous forests; • contractors, farmers, forestry workers should make sure all plant, equipment and vehicles are thoroughly clean before moving to areas which are free of the weeds. Throughout New Zealand residential development, foresty and farming are creeping closer to indigenous forest. New Zealand's native bush is in all our hands. Control over what we grow in our gardens is one part of its protection.