Old man’s beard clean-up in the Catlins

Writer Diana Noonan recently found the weed Clematis vitalba, known as old man’s beard, in a local forest reserve. She immediately got on the phone to DOC and was impressed by the Owaka team’s quick response.

Old man’s beard is a rampant climber that can put on 10 metres of growth in a single year and blanket an area of 180 square metres. The resultant smothering mass of greenery blocks out light, eventually killing the very plants that support it. If this isn’t bad enough, the monster seeds profusely with its potential progeny remaining viable in the soil for several years.

Clematis vitalba, known as old man’s beard

Given the weed’s ability to wipe out swathes of native growth, you can well imagine my reaction a few weeks ago when I spotted it growing in one of my favourite areas of forest reserve.

The Catlins Coastal Rainforest Park in South Otago is virtually free of this menace but now, right in front of me, a huge curtain of the stuff, growing as high as a two-storey building, was creeping its way over a 20 metre area of kamahi, rata and a dozen other natives growing close to sand dunes.

If old man’s beard wasn’t so easy to spot, I might have missed it altogether, but in late summer its flowers give it away. Unlike its welcome native cousin puawananga, which blooms in early spring, old man’s beard is covered in small, relatively insignificant looking, cream-coloured flowers. Once these develop into seed heads, they can be easily be mistaken for those of puawananga.

Old man’s beard flowers.

Old man’s beard leaves.

Having poked around the vine long enough to confirm my sighting, I sped home and telephoned DOC staff in the small township of Owaka. They were as horrified as I was, and determined to do the clean-up job properly, Biodiversity Ranger Emma Bardsley contacted Invercargill staff for expert advice.

Putting paid to old man’s beard requires thorough treatment of the affected area plus annual check-ups when herbicide is used to treat any remaining growth. When cutting the vine, both severed ends must be treated with herbicide. This is because even a trailing section still hanging mid-air will grow again if it makes contact with a suitable spot. This might be a damp cleft in a trunk or a patch of forest debris caught in the crook of a branch.

Herbicides were in use when I called by to watch DOC staff at work on the clematis a few days later. Emma and colleague Ray Shanks were busy with the secateurs while a volunteer assistant from the Science Teacher Leadership Programme of the Royal Society, armed with fluoro-tape, was marking out the area of invasion so staff making annual checks in the future would know just where to look. Ray pointed out some of the vines he was severing and I was astonished to see they were 5 centimetres in diameter. Emma eyed the sky hoping the good weather would hold for the clean-up as working in rain isn’t ideal given a heavy deluge (not unusual in the Catlins) can soon wash the herbicide off the cuts.

Applying the herbicide

DOC ranger Emma Bardsley and volunteer Emma Longmore

As well as dealing with the physical work of destroying the weed, Owaka DOC field staff will also be involved in making the local community aware of the invasion. Now that old man’s beard has been identified as attempting to set up home in the Catlins, Emma will be adding it to the list (DOC will also map the location of the infestation and keep it on their register so staff will be reminded to check the site again at regular intervals). There’s also the opportunity of tapping into the local community association’s database to alert everyone living and holidaying in the area of what to look out for should it strike again.

Old man’s beard in flower

By the time I leave the DOC staff to their work, I’m confident they’ll have capably completed the job by the end of the day, so it comes as a bit of a surprise when I receive an email later in the week from Emma. Work, she tells me, has temporarily ground to a halt, and for good reason. It turns out that all the time she and her colleagues were working at the site, they were virtually standing on top of a wasp nest. As soon as it has been dealt with, work will begin again on the ousting the climber. Emma is adamant she and her colleagues will finish off the job before the vines’ flowers set seed, but for now, at least, it seems that exotic species, both flora and fauna, are giving DOC staff in Owaka a run for their money!  

Diana Noonan’s article first appeared in Kiwi Gardener magazine, Issue 439.

War on Weeds

Hundreds of invasive weeds are smothering our native forests, wetlands and coastal areas, harming our wildlife and transforming our natural landscapes. DOC and Weedbusters have teamed up to fight the War on Weeds. Old man’s bead is one of the ‘dirty dozen’ problem weeds being targeted as part of the campaign.