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18 Aug 2021

Crathes Garden blog #4: carnivorous plants and new discoveries

Written by Susan Bennett, garden guide at Crathes Castle, Garden & Estate
A rare of tall, slender carnivorous plants grow beside a pool in a garden. The plants are shaped a bit like long, thin trumpets, and are growing in a bed of white moss.
New carnivorous plants in the Evolution Garden
Over the next few months, our expert garden guide is sharing a blog offering a behind-the-scenes look at what the team are working on in the garden at Crathes. Here is Susan’s entry from August with a look at some of the new discoveries she has made.

There’s a definite air of excitement as we view the dipping pool and its new carnivorous plants. In Scotland we have some native carnivorous plants – sundews, butterworts and bladderworts – but these North American plants are monsters in comparison. Some will grow to over a metre in suitable conditions. Both they and the Scottish plants seem to work on the same principle; or rather they have evolved to fill similar niches: boggy places with poor nutrients where they thrive because they supplement their diet by eating small animals – mainly insects. The butterwort and sundew leaves close up and trap small insects; bladderworts are water plants that trap small crustaceans such as water fleas and aquatic insects like midge larvae. The larger American plants have developed pitchers into which insects, and the like, fall and are dissolved in a ‘soup’ of enzymes.

The dipping pool plants are of two separate genera, Sarracenia (pitcher plants) and Darlingtonia (cobra lily). We have five different Sarracenia at Crathes: S. purpurea ssp purpurea, S. purpurea ssp purpurea var. heterophylla, S. oreophila, S. flava ‘Red Burgundy’ and S. flava var. ornata (stocky form). Their flowers are similar yet unusual. The petals, which hang down, had already been shed when the plants arrived in the garden, although new buds are forming. What we see now are three bracts and five sepals above the stamens and ovary. The style is expanded into an umbrella-like shape with the receptive stigmas on the pointy bits of the umbrella. The flowers seem to be adapted for cross-pollination, with flies crawling into the umbrella shape and getting dusted with pollen. The flower is said to have a ‘cat pee’ aroma.

The Darlingtonia californica does not have any flowers as yet; its leaves are also pitcher-shaped, but with a moustache-like attachment.

Because their habitats are threatened by modern agriculture and development, and people like to dig them up, carnivorous plants are not so common as they once were. One species, Sarracenia oreophila, is listed by the International Union for Conservation of Nature (IUCN) as ‘Critically Endangered’. The Crathes specimens were, of course, raised in a reputable nursery.

These plants will only thrive in poor conditions and in natural rainwater. Our Head Gardener James garnered a small amount of sphagnum moss from the estate to add to some gritty compost for the growing medium. However, it seems as if the moss has imported some midge larvae into the pool, since they are now in the pool in their thousands; our other ponds do not have these larvae in such a quantity. We have to hope that the pitchers will do their stuff and eat some midges. I don’t think the damselflies will be attracted to the pitchers, but they might well also eat the midges. Maybe some frogs, bats and house martins will eat more, but I fear the gardeners will suffer.

I have seen a few of the large red damselflies (Pyrrhosoma nymphula), both around the dipping pool and beside the Woodland Garden pool, where the water lily is looking very beautiful. The pond weed here, which I think is the native spiked milfoil (Myriophyllum spicatum), is spreading rapidly. The milfoil is one of the oxygenating plants that helps to keep the pond healthy by making sure that the water does not stagnate. It also provides a good habitat for developing wildlife. The flower spikes are insignificant by any yardstick. In North America this milfoil is invasive and difficult to control. I don’t think there’ll be any problem with the North American carnivorous plants getting out of control here. They are known to naturalise in parts of Ireland but not in Scotland. James will be keeping an eye on the ditch, where the excess water from the dipping pool may end up, but there’s no connection to any water course further afield.

I fancied a wander along the back forestry road this month, hoping to see lizards and perhaps the golden-ringed dragonfly, but no luck. However, there was plenty else to see. Speckled wood and ringlet butterflies accompanied me along the way, but were too flighty to photograph. I did manage to catch the meadow brown and found a small heath caught in a spider’s web. The meadow brown had a bit missing where I think a bird had tried to catch it and was fooled by the ‘eye’ on the wing (instead of pecking at the juicy body), thus letting the butterfly live a little longer.

Another day I saw what I think is an ichneumon wasp struggling in a similar sort of web – I didn’t see the spider though. There are many different types of ichneumons, but generally they parasitise caterpillars by laying their eggs into the caterpillars; when the ichneumon larvae hatch, they feed on the caterpillars. Further on, I spied a tiny iridescent leafhopper, possibly Cicadella viridis – it was so beautiful. Grasshoppers were frequent in the grassy places – providing the sound of summer; the one I caught with my camera is, I think, the mottled grasshopper (Myrmeleotettix maculatus).

I came across a patch of beech fern (Phegopteris connectilis), which I have not previously noticed at Crathes. This fern remains small and is easy to identify because the two bottom pinnae point away from the apex of the frond. It grows in woodlands, but is not particularly associated with beech trees. It has been too dry for many fungi to be evident, although I expect the recent downpour will change that. I did see what I think is the deadly poisonous panther cap (Amanita pantherina) and the stinkhorn (Phallus impudicus), still covered in gloopy spores with a bluebottle acting as suitable spore dispersal agent.

It’s the endless connections and adaptations that make the natural world so fascinating. Being in the process of moving house, I’ve been thinking about tidiness. A friend used to say ‘a place for everything and everything in its place’, but I am not much good at the second part of the saying. Latterly, I have been thinking of the planet in a similar way: so much is beautifully adapted to its niche. Even the highland midge has its place – it’s estimated that a pipistrelle bat can eat as many as 3,000 midges per night. But it’s not quite that simple. ‘Everything in its place’ suggests a stability, even a stagnation, whereas we know that in the natural world everything is fluid; evolution continues. At Crathes, with so many new plants appearing in the garden, it’s difficult to keep up with all the adaptations that contribute to the biodiversity of the planet.

This month I have been finding out more about gingers. The ginger that we most commonly eat, Zingiber officinale of the Zingiberaceae family, is not found growing wild, but only exists in cultivation and as such is known as a cultigen. Ginger is thought to have been first cultivated in maritime Southeast Asia, maybe 5,000 years ago, and then traded, reaching Europe in Roman times. Some of the gingers that grow in the Evolution Garden are of the same family as the edible ginger: Cautleya spicata ‘Crûg Compact’ and Roscoea cautleyoides ‘Crûg’s Late Lemon’. Both are alpine gingers.

Three small plants grow in a row in a bed. They have waxy long leaves and delicate white flowers on top of their stem.
Roscoea cautleyoides ‘Crûg’s Late Lemon’ in the Evolution Garden

Crûg Farm, near Snowdonia, belongs to Bleddyn and Sue Wynn-Jones, who turned from beef farming to building a specialist nursery business. Each year they spend time travelling and collecting rarities for their nursery. The seed of ‘Crûg Compact’ was collected in 1994 in the Lachung Valley, in Sikkim, near to the Indian border with Tibet. The seed of ‘Crûg’s Late Lemon’ was collected in the Lijiang area of Yunnan, China, in 2000. There is another of Crûg’s gingers growing in the Crathes cold frames – Roscoea tibetica f. atropurpurea – which was collected in 2000 in the Birong Valley on the Sichuan-Yunnan border.

An online research paper gives information on the evolution of these alpine gingers and their distribution, which appears to be a result of continental (tectonic) drift. [1] The ginger family originated about 105 million years ago, in the middle Cretaceous period. Radiation of the species was rapid in the late Cretaceous. Today, 95% of ginger species are found in lowland tropics, but our Crathes genera are found high up in the Himalayas and adjacent regions. Like the cultivated ginger, roscoea seeds are dispersed by ants. A little fatty or starchy attachment to the seed, called an elaiosome, is attractive to the ants as a food. The ants then carry the seed to their nests, helping with dispersal.

The wild gingers of North America belong to a different family and genus, but taste similar to the true Asiatic gingers (although eating them is not advised). They belong to the genus Asarum of the Aristolochiaceae family. Checking my notes, I see that we have Asarum megacalyx in the Evolution Garden – a Japanese big flowered ginger – which has evergreen leaves useful for ground cover and unusual dark purple/brown flowers. I look forward to watching it grow.

A close-up of a plant growing in a pot. It has long waxy leaves, a long stem and a bright purple flower at the top.
Roscoea tibetica f. atropurpurea in the cold frame

The lilies in the Evolution Garden have flowered already. Lilium ‘Pan’ is one of the Asiatic North ‘Greek Gods’ series which, like the ‘North Ladies’ series, was developed by Christopher North and his wife Marie. Please see one of my earlier blogs, from August 2020, for more information on this. ‘Pan’ looks similar to ‘Karen North’ but is paler.

Also new to the garden, and to me, are the unusual pineapple lilies (Eucomis sp.) that are in flower beside the glasshouses. I am much taken with these lilies, which belong to the Asparagaceae family.

The calla lilies (Zantedeschia sp.) that are now on show in the glasshouse belong to the Araceae (lords-and-ladies) family and are related to our native arum lilies. One of the species, Zantedeschia aethiopica, is hardy and grows outside. It has occasionally naturalised in the south of Britain. The flowers are held on a rod-like spadix and surrounded by the petal-like spathe. Since they come from South Africa, most calla lilies are tender.

The Arisaema sp. growing in the South Border, now covered in red berries, is of the same arum family. The skunk cabbage is another arum, as is the Amorphophallus genus – we have the devil’s tongue (Amorphophallus rivieri) from western Yunnan growing in the glasshouse. The famous Amorphophallus titanum can grow to a height of about 3 metres and is known as the corpse flower because of its colour and smell of rotting flesh, which attracts flies and carrion beetles for pollination. There was one blooming in the Royal Botanic Garden Edinburgh glasshouse a couple of years ago, although it was not quite ripe when I saw it and it had not developed its foul smell. The flowering, which is unpredictable, is usually an item of news because of its size and stench. This plant is a curiosity at botanic gardens across the world, where scientists and horticulturalists are finding out about its place in the world. Its native habitat is in the rainforests of western Sumatra on steep mountain sides. Due to excessive logging in the area, it is considered Vulnerable on the IUCN list. It will be a great shame if it becomes another of those plants that loses its natural place and is only known in botanic gardens.

Updates

  • The much-needed rain came in torrents ... and created drainage problems, both outside and inside the walled garden. Davy has been busy with various diggers and tractors trying to sort the blockage by the garden gate. Inside, the gardeners have been repairing the washed-away paths, a regular occupation. Gravel has washed into the dipping pool, signalling a need for a small barrier to divert the flow away from the pool.
  • There has been a dearth of butterflies in the Walled Garden this year. I was pleased to see a comma butterfly (a recent incomer in Aberdeenshire) on the buddleia, but generally the butterfly numbers are extremely worrying.
  • There are plenty of clematis in flower just now, some on the outside of the garden wall.
  • The eucryphias are now beginning to bloom in the Upper Pool Garden – always a show and very popular with the bees.

[1] Jian-Li Zhao et al, ‘Evolutionary diversification of alpine gingers reflects the early uplift of the Himalayan-Tibetan Plateau and rapid extrusion of Indochina’ in Gondwana Research, vol. 32, April 2016, pp. 232–241

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