Carnivores one and all

As a young boy in The Netherlands Cor Schipper’s class was shown a carnivorous sundew (Drosera) plant by his teacher – a spark that has ignited a lifelong passion for the retired entomologist.

Cor, now 81, and wife Hetty left their homeland in 1963, living in Australia and Samoa before coming to New Zealand and, after a stint in Wellington, settling in Rotorua in 1971.

A founder member of the New Zealand Herpetological Society, Cor kept snakes, toads and lizards in Australia – “but we started a family there so that was a different kettle of fish” – and in Samoa rescued baby fruit bats after their mothers had been killed for food. “We reared them on chocolate milk, which it turns out they like,” he says. “We taught them to fly by moving the chocolate milk further away each time. When they could fly, we let them go.”

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Cor Schipper with a Nepenthes vine. Photo: Sandra Simpson

Cor has always been interested in the natural world so it’s not surprising that his hobbies and work – mass breeding insects for research and working on biological controls – sometimes overlapped. His collection of bromeliads, which began in Holland, was thanks to a gift of tropical frogs – it turned out they would lay eggs only in a bromeliad.

Although he had sundews in Holland, his life-long passion for carnivorous plants was fully realised when he came to New Zealand, and listening to Cor describe the mechanisms used to trap prey – primarily scent, colour and nectar – it’s easy to see why he finds them so fascinating.

But why have these plants evolved in such a striking fashion? Although they can be found in a wide variety of climates and elevations in many different countries, they all have one thing in common. They grow in nutrient poor soils or water-logged conditions and so need to extract minerals and nutrients for growth from another source.

Another commonality is long-stemmed flowers, well above the plant, to protect pollinators from falling victim to their deadly “charms”.

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Sarracenia pitchers. Photo: Sandra Simpson

Sarracenia (pitcher plants), found in boggy areas of the eastern United States, “dope” their nectar with coniine, a chemical found in hemlock. “If you put nectar in a petri dish with ants, the ants go all wobbly,” Cor says. “The hairs of the Sarracenia tube face downwards to guide the ants down, then there’s a slippery patch on the tube wall so they fall into the liquid at the bottom. The liquid has a surface like soapy water, so instead of floating the ants fall straight through, and the chemicals in the liquid take care of the body.”

The flowers of the Sarracenia, like many carnivorous plants, grow high above the plant so pollinators don’t fall victim.

A Venus flytrap (Dionaea muscipula) won’t react if the hairs inside the hinged trap are touched once. Touch them twice, however, and it snaps shut in a fraction of a second. “The plant wants nitrogen, phosphate and potassium so it removes the enzymes it needs from its prey but leaves the exo-skeleton. When the process is finished the trap opens ready for the body to wash out in rain.”

Don’t be tempted to set the traps off – do it more than twice on the same trap and it will likely die.

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Nepenthes pitchers. Photo: Sandra Simpson

Nepenthes lowii (a pitcher plant vine) from Borneo exudes a sweet, fatty substance to attract small mammals – as the animals feed they excrete into the pitcher and so feed the plant.

“The variety of carnivorous plants is astonishing,” Cor says. “In the Nepenthes family alone there are well over 100 species with pitchers that range in size from 3cm long that specialise in catching falling compost from trees, often carrying insects, to Nepenthes rajah, the largest carnivorous plant in the world which has pitchers the size of a rugby ball.

“While most Nepenthes attract ants, there is one that attracts termites and some that can digest small rats and shrews if they fall in – that happens generally during a dry period when  animals come to drink from the pitchers but are a bit weak and fall in.”

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The floating trap system of Utricularia intermedia, a bladderwort. The tiny hairs in the water are sophisticated suction traps (bladders) designed to provide a nutritious animal meal for these rootless floaters. The size of the bladder is microscopic, ranging anywhere from 0.1 mm to 5 mm, depending on the species. Photo: Sandra Simpson

One of the most fascinating carnivorous plants, in Cor’s view, is also one of the smallest. The rootless Genlisea family (corkscrew plants) set their traps underground. “It’s semi-aquatic and grows in moss or mud and although it has leaves above, it also has modified leaves extending below the plant. Each ‘leaf’ has forked, hollow spirals that exude a chemical to attract prey. The prey climbs up the spiral with the hairs growing upward to guide it.

“In Brazil in the last 5 years they’ve found Philcoxia minensis, a carnivorous plant that flowers above the soil but has all its sticky leaves underground where it catches nematodes.”

Over the years Cor has done some of his own breeding, particularly of Sarracenias. “I’ve been working on one for about 25 years, but when you work on your own it’s not always done as scientifically as it should be in terms of record keeping. I lose patience sometimes.”

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Sundews coat themselves in drops of nectar. Once an insect is stuck, the leaf  rolls up around it to digest it. This is Drosera cisitflora, native to southern Africa. Photo: Sandra Simpson

Living on a hill above Rotorua, his home cops some decent frosts but the Sarracenias and Venus flytraps stay outside year-round. “They can both freeze but will come back in the spring, no problem,” he says. “And most of the sundews have a winter dormancy, although Drosera auriculata, a New Zealand native, has a summer dormancy

“There’s a huge temperature-tolerance variation among all the families so it’s worth researching – for instance, most Nepenthes are tropical and need to be kept inside but there’s one from a mountain in New Guinea that can stand a bit of frost.”

His rare Darlingtonia californica, still a tiny plant, requires special attention. Closely related to Sarracenias, it grows only in northern California and Oregon on the sides of streams fed by meltwater. “It’s very difficult to grow because it likes warm leaves and cool roots, maybe a difference of 15°C. I have to feed it ice cubes every day.”

Unfortunately, carnivorous plants aren’t the answer to a garden’s whitefly, ant or mosquito problem. “Research has shown they collect about 5 per cent of what’s around,” Cor says. “So they’re not a great biological control – instead, enjoy them as another example of nature’s wonder.”

Growing Tips:

  • Pot in a mix of peat moss and coarse sand, or peat moss and pumice (perlite) or plant in plain sphagnum moss; plants generally prefer a low pH mix.
  • They don’t like hard tap water so use rainwater whenever possible. Many grow in swampy areas so like to be kept moist and prefer to stand in water (hanging pots should have a fitted saucer).
  • Check whether your plant needs summer-level watering over winter (most don’t, but some do).
  • Before putting a plant outside, check whether it is frost tolerant – many are, but many aren’t.
  • Plants outside don’t need to be fed. But for indoor plants catch flies and cockroaches to feed the plant. Don’t use flyspray to kill insects you intend to feed to the plant.
  • Cor keeps small, delicate plants, such as sundews, inside “otherwise blackbirds peck them out of the pots and I lose the plant”.

This article was first published in NZ Gardener and appears here with permission.

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