‘Terrible season’ for Christchurch’s hungry monarch caterpillars
People desperate to feed hungry caterpillars in their gardens face a national shortage of swan plants.
The sought-after plants are the main diet of monarch caterpillars, which build chryalises and, once they are butterflies, lay an average of 700 eggs each on the underside of the leaves. Each caterpillar needs to munch enough to grow almost 3000 times its size over two weeks. The dearth of food is causing mass starvation and death.
Mitre 10 Mega Papanui garden centre worker Lucy West said the store was selling out of plants as fast as they came in.
‘‘Everyone’s on the hunt for them. It’s good people are getting on to it, but it’s hard when we can’t provide.
‘‘We’re waiting for the next shipment in a couple of weeks, but the growers just can’t keep up.’’
West said due to the colder winter the season started slightly later than usual and ‘‘everything’s a bit behind schedule’’.
The demand for this time of year was unprecedented, she said.
Riccarton Bunnings Garden Centre nursery employee Sinead Biggs said the plants had been sold out for more than a week.
‘‘There aren’t even any we can order, so yeah, they’ve been very, very popular this year.’’
Some customers were returning to Cashmere Oderings Garden Centre every day to buy a new plant as their caterpillars chomped through the leaves overnight.
They had a few plants left in store, but they were ‘‘incredibly’’ popular, an employee said. A 10-centimetre plant cost about $5.
Monarch Butterfly New Zealand Trust spokeswoman Jacqui Knight said because of the longer, wetter winter, plants had died as slugs and snails attacked.
It was a ‘‘great season for monarch butterflies’’ because the wasp population – a caterpillar predator – was down, but a terrible season for their young, she said.
‘‘From what I’ve heard, the growers aren’t growing any more either, so when it’s gone, it’s gone.
‘‘We have all sorts of trouble every year, but it’s certainly much worse this year.’’
Marcia Butterfield has half a dozen swan plants on her Christchurch property, including two grown from windblown seeds.
Caterpillars often overwhelmed the plants and, at times, some were culled for the ‘‘greater good’’, Butterfield said.
‘‘We sometimes have to squash the babies to give the bigger ones a chance, otherwise they’ll all starve to death. It’s pretty grim.’’
Knight said people needed to be educated on how to grow their own swan plants as there was no alternative feed option.
‘‘A farmer won’t go out to buy more cows if he doesn’t have farmland and feed. He makes a good crop of hay early and he can use that over the season to look after them.’’
The Palmers Garden Centre website recommends growing plants in full sunlight, in a welldrained, sheltered spot.
‘‘Once the butterflies have laid their eggs, you might find you have too many caterpillars for the size of the plant. It is amazing just how many leaves they can munch,’’ it says.
The monarch butterfly starts as an egg, which hatches as a caterpillar (larvae), which eats swan plants, then forms a chrysalis and, finally, emerges as a butterfly.