With spring here, butterflies are laying eggs on swan plants around the region – but a Tauranga expert of the winged beauties says they're flying under threat from nature and humans.

Mary Parkinson, who runs Te Puna Quarry Park's butterfly garden, says many species battle against nature's weather conditions plus human activities and products.

Mary Parkinson with some of the winged beauties at the Te Puna Quarry Park butterfly garden she runs. Photo: Tracy Hardy.

'It's a bit hard for butterflies because nature controls their life or death – cold wind or rain will put them back,” says Mary.

'But sprays used in gardens can also kill them as well as other insects.”

The Monarch Butterfly Trust member says humans can also be a predator.

'Some people collect butterflies like they collect stamps and put pins through them.

'So the people who love them can also be the butterflies' worst enemies.”

Species such as the monarch butterfly don't mate in autumn – they hang clustered together in trees for four months then mate and lay eggs in spring.

Mary says butterflies' biggest threat is wasps brought into NZ to control the white cabbage butterfly.

'The admiral butterfly's chrysalis looks the same as a cabbage butterfly chrysalis, and wasps can inject an egg into the admiral's soft chrysalis.

'Another wasp species brought in by mistake lays 30 or 40 eggs, so if you're breeding admirals you can lose your whole breeding programme if one gets near.”

The monarch butterfly's problems are ants eat eggs and paper wasps eat caterpillars for protein to build nests.

'They will suck the caterpillar dry,” says Mary, who recommends spraying wasps and nests with fly spray.

'There's also praying mantis and shield bugs that will suck caterpillars dry.”

Plus sprays on milkweed plants can be an issue.

'People buying swan plants need to make sure they haven't been sprayed.”

Mary says people can help butterflies by keeping sprays away from milkweed plants so caterpillars don't get poisoned.

'You can also nip back swan plants to about half-a-metre high and take the top out, so you've got a bushy tree offering caterpillars more protection and shelter from wasps.

'Some people cover branches with an old curtain – I hatch my caterpillars in a plastic container.”

For the quarry, Mary hatches 'thousands” of butterflies, tags them from March 1 then releases them.

Helping adult butterflies means growing the right nectar plants for them.

'Old-fashioned cottage garden plants have more nectar,” says Mary.

She's at the quarry park's butterfly garden on Tuesday and Thursday mornings if people want to learn more.