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An invasive weed that likes wet conditions, and is a major concern in waterways is currently popping up everywhere on the Hibiscus Coast.
Called alligator weed because it lurks in wet places, it spreads easily. It is very hard to kill and therefore expensive to control.
Ben Rogers, who looks after maintenance and gardening at Red Beach hospice, has seen the weed take off, invading the lawn and garden areas largely because the soil is wetter than normal.
“We’ve had it in the garden for the last couple of years, but it has become a huge problem after the wet weather,” he says.
Many of the normal weed removal techniques, particularly organic ones, have been unsuccessful.
When it is in the lawn, mowing cuts it into pieces which can then regrow. Mulching helps suppress the weed, but as soon as light comes through, it pops up again.
A pile that Ben pulled out by hand and put in black plastic bags in a garage to rot was still alive a month later.
He says a beetle that eats alligator weed in other countries has proved unable to handle NZ conditions and so cannot be introduced here.
Ben likes to garden without toxic sprays, but he’s reluctantly had to resort to glyphosate to try and kill alligator weed.
Worryingly, Ben has seen it growing in D’Oyly Reserve waterway recently.
“That’s scary, as it takes over and blocks silt from moving through,” he says.
He says it is also all over the Coast, on public berms and in gardens.
He recommends pulling it out, dumping it in a pile and spraying the pile over time until all of it is dead.
Alligator weed, originally from Brazil, has been in NZ since the early 1900s.
“It’s really taking hold on the Coast. The more people that are aware of it and can remove it the better,” Ben says.
What can you do? Auckland Council’s biosecurity principal advisor, Dr Imogen Bassett, did her PhD on alligator weed. Here’s her advice: • Alligator weed can grow from just a small fragment of stem or root. Therefore, to prevent further spread it’s really important to make sure there aren’t fragments of alligator weed contaminating soil or other materials that are moved between sites. • It can be tricky to control once it’s on your property. If it’s just recently popped up, consider getting onto it quickly before it gets too much of a foothold. For small infestations, you may be able to dig it out. Larger infestations will likely require herbicide use. • Alligator weed is a pest plant under Auckland’s Regional Pest Management Plan, meaning that it’s not legal to distribute it to new locations. However, you may dispose of pest plant material to landfill or secure green waste facilities. • For more detailed advice visit Auckland Council’s Pest Search website – www.tiakitamakimakaurau.nz/protect-and-restore-our-environment/pests-in-auckland/pest-search/altphi/
