Conservation Comment: Who's responsible for weeds?

USES of photography in conservation comprised my Conservation Comment on February 15. I started today's article in late April as certain weeds became conspicuous - flowering Madeira vine, seeding old man's beard and pampas grass.

Sometimes we don't realise how many weeds there are around us until they flower or seed. Photographs can show the presence, extent and spread of weeds. Horizons Regional Council (HRC) has outlined its strategies for weed control in its 2015-2035 Pest Management Plan and Strategy (PMPS). Control of each weed needs a different approach, but a universal principle is that a weed's control should begin with the first plant seen, not after it has become widespread.

Let's look at photos of one example, Madeira vine (Anredera cordifolia). This aggressive and smothering climber has concerned me for years. In 2002 I made a submission on it to the Wanganui District Council's (WDC) annual plan. At the hearing, I presented each committee member with a piece of Madeira vine to show how its stem tubers drop off and start new plants when touched. It does not set seed in New Zealand. It spreads mostly from dumped garden waste and, consequently, is mostly on the downhill side of roads.

My request in 2002 to WDC was for free green-waste collection areas to limit the spread of Madeira vine and other weeds. Charging people to dump green waste encourages illegal dumping, with subsequent weed spread.

Weeds could be shredded, hot composted and sold to residents. What happened to my free green waste proposal? Nothing. There are now more sites infested with Madeira vine than 14 years ago. You can see it on the slopes of Cooks Gardens, beside the Opera House. In 2001 the plant in my photo was on one private section and over the fence into adjoining WDC land. By 2016 this patch had spread along boundary fences to at least four properties. Over 15 years, contractors have done intermittent control of Madeira vine on the WDC land, but regular monitoring and follow-up control are critical.

WDC is responsible for weeds only on land under its control. That brings me back to HRC. At biosecurity.govt.nz read "Contact your regional council to determine the status of [weeds] and responsibility for control and/or advice on control". I have a well-researched HRC report on Madeira vine in our region, published in 2010. Have you seen it? Even Googling doesn't reveal it. HRC's 2007 regional pest management strategy listed Madeira vine as "Priority 4: management objective decided by November 2011". What was the decision? The draft 2015-35 PMPS doesn't mention Madeira vine!

Different parts of the 165-page draft have no fewer than eight lists of weeds; finding whether a given weed is on any list, or none, is difficult, and it omitted 100 or so other weeds named in the 2007 plan. But "in recognition of its regional leadership role under the Biosecurity Act", HRC makes landholders responsible for many weeds.

At least, we need a single table listing all the weeds in the PMPS. Each weed needs a note as to what weed category it is in or why it has been omitted.

-Colin Ogle is a volunteer "weeder" and retired ecologist.