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A Tour of Chester Zoo's Nepenthes Collection
13 June 2018
Chester Zoo is home to one of the largest collections of carnivorous plants in the UK. Their National Plant Collection of Nepenthes holds over 2500 individual plants from 130 species and countless hybrids, many of which are facing imminent extinction in the wild.
Last week I visited Chester Zoo for a behind-the-scenes tour of their three glasshouses, which are not open to the public, with Lead Horticulturist Paul Leach. He’s been growing Nepenthes at the zoo for over 20 years and has been responsible for the National Collection since Chester first acquired it from Derek Clavell-Bate in 2011.
The decision to buy the collection - which already contained a number of highly endangered species - can be traced right back to the zoo’s mission statement: ‘preventing extinction’. The collection not only highlights the threats posed by habitat destruction and poaching, but has also enabled the zoo to make invaluable contributions to vital conservation projects. Paul explained: “We have already sent cuttings of N. kampotiana back to Thailand to help with a re-population project, and there are other projects in the pipeline for other species.”
Today the collection is spread across three glasshouses, each representing a different environment: lowland, intermediate, and highland. My tour began in the highland glasshouse, the largest of the three.
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The highland glasshouse is controlled by an automated system which manages the heaters, roof vents, and lights. The environment is kept at around 24°C during the day and 14°C at night, in contrast to the lowland house which is kept at a constant 30°C. Watering with rainwater is done by hand every day, but supported in the highland and intermediate glasshouses with an overhead misting system.
One of the things which struck me while exploring the glasshouse was the sheer size of many of the plants. Paul explained that he refrains from pruning scrambling vines and instead allows the plants to grow naturally, staking larger specimens with canes to support them. As well as making great use of the glasshouse’s height, it also means that the contrasting morphology of many species’ lower and upper pitchers was displayed to full effect. Cuttings are typically only taken as a way to build up numbers of rarer species as a safeguard.
Most of Chester’s Nepenthes are grown in a peat-free mixture, but Paul is always open to trying new mixtures. “I normally use a mix of sphagnum moss or new Zealand sterilised moss with perhaps moss peat or bark, perlite, or silver sand maybe added at times. I always need vast quantities for the collection!”
When it comes to fertilization, Paul is a fan of experimentation. He’s tried numerous different approaches including the famous coffee method, much to the confusion of the zoo’s catering team. Today, however, he typically relies on Osmocote: he drops one or two pellets into a single pitcher on each plant per month. The plants certainly seem to appreciate being fed like this, with most of the larger plants holding dozens of colourful pitchers at once.
Next, we entered the intermediate and lowland glasshouses.
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Given the number of plants which were at varying stages of flowering, I asked Paul whether he and his team ever propagate from seed. Given the size of the collection and the length of time it takes to raise mature plants from seed, typically only very specific plants are prioritized for pollination and seed collection. “We do hold seed and/or pollen at times, and we are always open to exchanges as long as everything is legally obtained,” he elaborated.
While the Nepenthes glasshouses are not currently accessible to the public, the team have experimented with integrating certain specimens into public areas. This includes a particularly fantastic display overhanging the cliff face in the Monsoon Forest area. Public displays such as these usually involve hybrids, partly to avoid risking individual species, but also because hybrids are more likely to tolerate the occasionally suboptimal conditions found in the animal houses.
“The response to these plants has been amazement and surprise; people do not often see these plants anywhere else,” Paul observed. I also spoke to Phil Esseen, Curator of Botany and Horticulture, who explained that striking and unusual plants like Nepenthes are being tested as a way to combat ‘plant blindness’ - the tendency for visitors to overlook plants completely. While perhaps inevitable to a degree given the setting (many visitors to the zoo arrive with the specific intention of learning about animals) staff are keen to raise awareness of threats to biodiversity and the importance of conservation for all lifeforms, including plants.
During my day at the zoo, I was also treated to a tour of the new outdoor Sarracenia display and orchid house and with Phil Esseen, and of the impressive cacti collection with Lead Horticulturist Jo Adderley. A select handful of my photos are presented below.
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Before leaving the zoo I asked Paul if he’d share a few tips for Nepenthes growers. He emphasised that there was no one-size-fits-all solution; the huge number of variables means you shouldn’t be afraid to experiment when looking for an approach which suits you. “The only tip I would offer to all growers is to regularly check your plants, daily if possible - spot problems early and they are easier to deal with.” My Nepenthes grow guide is available here.
I’d like to say a huge thanks to Paul, Phil, Richard and Jo for making me feel so welcome and for showing me round the zoo’s incredible collections. If you’d like to learn more about Chester Zoo’s important conservation work, you can visit their website. If you’re a member of the Carnivorous Plant Society, be sure to keep an eye out for Chester Zoo’s next Open Day.