GREENLIFE MATTERS
Beauty and the beasts
A captivating climber! Abundant and spectacular blooms. Large indigo blue flowers throughout the summer and autumn. An absolute star in a sunny spot. Looks spectacular clambering through other plants in a mixed border. Ideal to hide downpipes. Impossible to resist! These words, found on northern hemisphere websites, describe what is one of New Zealand’s most detested noxious weeds - Ipomea indica (aka ‘morning glory’).
But let’s be fair. One gardener’s weed is another’s treasure. For many UK gardeners frost tender morning glory is a prized ‘annual climber’ or greenhouse plant. It even bears the UK Royal Horticultural Society’s prestigious ‘Award of Garden Merit’. It’s easy to see why its seed might have found its way to New Zealand in the pocket of some plantloving early settler.
Of course lessons have been learned. New Zealand’s Biosecurity Act of 1993 significantly tightened our biosecurity rules (ironically 1993 was also the year morning glory received its Award of Garden Merit) and these days we are far more vigilant about what gets into the country. Morning glory has firmly secured a place on the National Pest Plant Accord (NPPA) list as one of the ‘unwanted organisms’ now prohibited from sale and distribution within New Zealand.
Other such ‘award winning’ lovelies listed on the NZ Pest Plant Accord include pink jasmine (Jasminum polyanthum), wandering willie (Tradescantia fluminensis), fleabane daisy (Erigeron karvinskianus), arum lily (Zantedeschia aethiopica) and Japanese honeysuckle (Lonicera japonica).
All of the above and other famous garden escapees, like Clematis vitialba (old man’s beard) are now well established noxious weeds listed on the NPPA. Many more are listed on regional council websites as invasive species in specific locations.
Despite being banned from sale for decades now, our most noxious weeds remain rampant in nature and in our gardens, dispersed far and wide by birds, animals, people, wind and water. They not only spread by seed, but also via small pieces of stem that take root
and grow, quickly smothering native vegetation. With climate change, weeds of warm-climate origin are on the move from north to south and are going to get all the more invasive if we take our eyes off the ball.
Most of us know wandering willie as the weedy groundcover that thrives in shade and outcompetes anything in its path. But as recently as the 1980s, it was a popular houseplant displayed in macrame hangers! Wandering willie forms thick mats, blocking the growth of native seedlings. Its brittle stems easily break into bits, which get carried along by water to take root in fresh ground. It is also transferred to new areas when garden waste is dumped on roadsides. Extremely difficult to get rid of once established, wandering willie is spoiling bush reserves throughout the North Island and in some parts of the South Island.
Controlling the spread of pest plants calls for dedication and commitment. Experts recommend using a combination of control methods tailored to tackle to each problem. Action plans commonly include hand weeding and digging, dense planting to shade out those weeds that need light, and where necessary the use of herbicide.
Be in to win Yates Zero Tough weedkiller (entry details on page 30).
Biological control, whereby a fungus or insect is introduced to control certain weed species, is a growing science already in use in New Zealand.