Plant Focus - Carnivorous plants

These ornamentals have wide appeal despite complex cultivation regimes, says Miranda Kimberley.

Dionaea muscipula - image: Floramedia
Dionaea muscipula - image: Floramedia

Carnivorous plants appeal to a wide range of people, from novices to scientists. They are fantastic ornamentals, ranging from outdoor varieties to slightly more tender indoor plants, although none make great houseplants because they cannot cope with year-round central heating. Most need a dormant period when they are in cool conditions for at least a few months.

The Venus fly-trap is the first variety people think of when it comes to carnivorous plants, possibly thanks to its starring role in cult film Little Shop of Horrors.

Breeders are currently developing larger traps - Dionaea muscipula 'B52' has gorgeous reddish-purple traps up to 6cm long.

A favourite group in garden centres is the North American pitcher plant, from the genus Sarracenia. They produce showy flowers and have tall thin pitchers, formed by modified leaves that are bright green, whitish, red or purple with varied degrees of veining and mottling. Most species and varieties are hardy outside in the UK.

Other notable carnivorous plants include monkey cups, Nepenthes, which are divided into highland varieties that are more tolerant of lower temperatures and lowland plants that need hot and humid conditions. Some make excellent hanging basket plants and can do well in a conservatory or bathroom.

Also worth mentioning are the smaller carnivorous cousins the Butterworts (Pinguicula species) or the Sundews (Drosera species). Pinguiculas have fleshy leaves that are covered in a sticky secretion and are an ideal biological control for whitefly. Drosera have glands tipped with a sticky mucilage to trap their prey - in the sunlight this substance looks like dew, giving them their common name.

The cultivation requirements of all the carnivorous plants are varied and complex. They come from all over the world, from the tundra to the tropics. Growers need to figure out from where the plant originates and treat it accordingly.

Most need good light to give plants better colouration, but while most like direct sunlight, Nepenthes prefer indirect. They need an acid medium, so peat or spaghnum moss is widely used. They cannot cope with lime at all so water type is important. Ideally use rainwater, but the hardness of the local water may need to be tested. General bottled water may have traces of lime but deionised water is acceptable.

Watering is tricky to get right. Most of the carnivorous plants are bog plants so they are happy in wet compost and even standing in water throughout the growing season with the compost allowed to dry out between waterings during autumn and winter. Others, such as Nepenthes and some Butterworts, Bladderworts and Sundews, prefer conditions a little drier.

What the specialists say

- Alistair Pearce, partner, South West Carnivorous Plants, Devon

"Carnivorous plants appeal to people who wouldn't normally be interested in plants. That's because they are seen to fall somewhere between animals and plants.

"Venus fly-trap is the biggest seller. There are now varieties available, such as our 'Southwest Giant', that have traps up to 5cm long. We're finding our younger customers are also keen on the Sundews and the North American pitcher plants. They love the fantastic flowers and use them in bog gardens and tubs.

"Winter dormancy and watering are probably the trickiest parts of growing carnivorous plants. In October/November, plants should be allowed to go dormant. They should be kept just moist at this point.

"During the active growing season they can be stood in about 1cm of water, but allow the compost to dry out between waterings. It should be rainwater, and failing that deionised or battery top-up water. General bottled water is best not used because it can have high levels of limestone."

- Frank al-Medenni, growing and marketing manager, Euroflora, Hertfordshire

"Carnivorous plants really stand out in garden centres. The most popular are the Venus fly-traps and the Sarracenia.

"We grow around 50,000 hybrids of all colours, shapes and levels of hardiness. Many of the ones we produce can take down to -20 degsC.

We grow a lot of the northern hemisphere species to suit our climate. We produce the highland types of Nepenthes, which can take low temperatures.

"While Sarracenia and Venus fly-traps like direct sunlight, the Nepenthes prefer indirect. Keep the plants moist at all times - if they dry out they will die. Don't fertilise them because it can kill the plants (although Nepenthese can be fed with low-strength orchid feed in the summer). One insect may provide enough sustenance for a whole year. They require an acid medium based on peat or spaghnum moss and need rain or soft water."

In practice

- Jon Rowbotham, outside planteria supervisor, Dunston Hall Garden Centre, Derbyshire

"Altogether we have 15 hardy varieties from the Sarracenia species. These include 'Cowboy', 'Pinky', 'Dracula', 'Rednecks' and 'Jedi'. Different varieties attract different pests in the garden. For example, Sarracenia (approx equal to) 'Tara' and S. purpurea attract slugs, while Sarracenia (approx equal to) 'Stevensii' and S. leucophylla attract more of the pests that fly. All of the varieties we sell are bee-friendly.

"The more unusual and colourful varieties sell very well. But there isn't really an out-and-out best seller. We hand out a care leaflet with each plant and explain the habitat they are used to. The varieties we stock are hardy down to -20 degsC.Carnivorous plants prefer a sunny position in a sheltered and damp situation.

"We display the plants in gravel trays with water and we have also used logs and moss to give the look of a boggy ground and their natural habitat. We have sign boards up explaining to customers their purpose of being in the garden."

Species and varieties

Venus fly-traps

- Dionaea muscipula is the single species from which all Venus fly-traps are bred. Nectar inside the traps lures prey including bluebottles and wasps and once the trigger hairs have been touched twice, the trap will close. The species has green traps with red inside and they are 1-4cm long. Interesting varieties include 'B52' and 'South West Giant'.

Sundews

- Drosera capensis is the easiest of the Sundews to grow. It forms a clump of thin green leaves covered with red gland stalks that roll up over the victim. It will do well on a sunny windowsill, conservatory or cold greenhouse. Can be grown outside in summer.

- D. aliciae is a rosette-forming Sundew. It has green leaves with red margins that are covered in glistening mucilaginous glands. Ideal for a sunny windowsill.

Monkey cups

- Nepenthes x ventrata is a hybrid that was the result of a cross between highland species N. alata and N. ventricosa. It is a good beginner's Nepenthes. It does not need high humidity to produce traps, which are a soft red colour and 20cm long. Ideal for a north-facing conservatory.

- N. ventricosa is one of the most hardy and easy to grow of highland species so ideal for beginners. It is low-growing with round, squat pitchers. Grow in a conservatory or warm greenhouse. Mist daily and provide light shading in summer.

- N. 'Rebecca Soper' is a vigorous hybrid that was the result of a cross between highland species N.ramispina and N. ventricosa. It produces attractive dark purple-maroon pitchers with pale-green insides. Excellent for hanging baskets.

Pitcher plants

- Sarracenia flava Award of Garden Merit (AGM) (H1) is easy to grow outside. It produces traps up to 1m high and large yellow flowers in the spring. They like full bright sun, water all summer and require three to five months dormancy each year.

- S. 'Jedi' produces small deeppurple pitchers leaning outwards, with hoods that curve over the top. Hardy enough for growing outdoors or in an unheated greenhouse.

- S. leucophylla AGM (H1) produces a pitcher that is green below but the top third is almost pure white with veins of dark red or green. One of the tallest Sarracenia. Hardy.

- S. 'Pinky' has pinky-purple colouring with distinctive veining. It can survive temperatures down to -20 degsC. Will catch wasps, earwigs and flies. Height and spread: Up to 50cm.

- S. purpurea is another species suited for growing outdoors. They are short, squat plants. S. purpurea ssp. purpurea, or the huntsman's cap, is extremely hardy and recommended for bog gardens. Slugs and snails can be found drowned in the traps.

Butterworts

- Pinguicula grandiflora is a small plant that resembles an African violet with deep-purple flowers in early spring. Grows best outdoors out of direct sunlight. Spends the winter as a small resting bud.

Thank you to Floramedia, which supplied the images for this article from its photo library

www.floramedia-picture-library.com


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