Source: Radio New Zealand
Monstera plants – and other invasive houseplants – are popping up in the wild, says University of Auckland ecology professor Margaret Stanley.
Stanley estimates about 20 introduced species begin breeding in the wild each year. It’s often not that plants are “escaping” homes, but people dumping them when they think they’re dead, are moving flats, or they’ve become too big, she says.
Dumping garden waste in reserves remains common, she says, and even a fruiting monstera planted outdoors can spread via wind or birds.
.
Indoor plants bred to tolerate shade and little watering are tough competitors outdoors, says Dr Imogen Bassett, Auckland Council’s head of natural environment specialist services.
Of particular concern are plants that have light seeds which can be carried by birds, roadside dumping of cuttings which can grow roots, and planting of hard‑stemmed species near native bush, Bassett says.
For example, some asparagus species – a common houseplant which is already a widespread invasive weed – have attractive berries birds like to eat and can be spread that way, she says.
What’s the risk?
Impacts vary, Stanley says. Woolly nightshade produces toxins in soil; vines like moth plant and old man’s beard can smother forests; Russell lupin can alter braided riverbeds.
“New Zealand’s most Instagrammed weed”, Russell lupin modifies the soil, according to University of Auckland professor of ecology Margaret Stanley.
Unsplash / Michael Kahn
Invasive weeds compete with native species for space, nutrients and light, Stanley says, and “plant blindness” means people often don’t notice them until it’s too late.
“Often because [introduced species have] arrived here without all the things that eat them, their specialist herbivores, they tend to be able to grow more quickly and are a bit more adaptable.”
How big is the problem?
Tradescantia – another plant that’s often at homes – is tolerant of dense shade, severe damage and grazing, wet, most soil types and high to low temperature, according to Weedbusters’ website.
Unsplash / Tadeusz Zachwieja
New Zealand has about 2500 native species and about 25,000 introduced species, with nearly 400 classed as invasive weeds.
Another 2500 introduced species are already growing wild, Stanley says.
Predicting which currently sold plants will become weeds is difficult, she says.
“Figs weren’t a weed until about 2005 when their pollinator also turned up in New Zealand and now they can set seed and spread.”
I don’t want my plant anymore – what do I do?
If you’re leaving plants outdoors to catch sunlight – take into consideration whether they’re fruiting and whether birds or the wind can pick those up. (file image)
Unsplash / Manki Kim
Stanley suggests paying for commercial garden waste collections.
Some weeds must go to landfill because they can’t be composted, she says. Council pest‑and‑weed search tools and the Weedbusters website can help offer more guidance on each species.
Some species are nationally banned by the Ministry of Primary Industries, but most bans come through regional pest management strategies which are reviewed every 10 years, Stanley says.
Tips when buying
Ask nurseries for sterile varieties.
Check council “plant me instead” recommendations for native alternatives.
View council guides on how to control each species.
– Published by EveningReport.nz and AsiaPacificReport.nz, see: MIL OSI in partnership with Radio New Zealand
