Oysterplant, Mertensia maritima

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Oysterplant, Mertensia maritima

Oysterplant (Mertensia maritima) and Sea Sandwort (Honckenya peploides) growing on Orkney.

A few weeks ago a lady from Northern Ireland contacted me and told me about some of the plants she’d seen for the first time in her local area in 2018, one of which was Oysterplant. It’s a favourite of mine, but a plant I rarely see.

Oysterplant, Mertensia maritima, is a beautiful perennial that grows on sand, gravel and shingle beaches. It grows close to the ground with a spreading habit, with blue-grey leaves and, from June to August, clusters of reddish flowers that turn blue as they age, in a similar way to Forget-me-nots and several other members of its family, the Boraginaceae. (I have previously written about some of these: Green Alkanet, Viper’s Bugloss, Navelwort and Abraham-Isaac-Jacob.) There are some lovely pictures of it on the West Highland Flora and UK Wild Flowers websites.

Mertensia maritima has a large taproot that reaches down through sand or shingle to find water, as well as anchoring the plant in its exposed habitat. In winter the leaves die back to ground level. The plant spreads by seed (nutlets) and these can be transported by wind and sea and have been known to travel at least 450 km (280 miles). Germination is unaffected by up to 18 days of immersion in sea water and the seeds are capable of staying dormant for several years, until the right conditions trigger germination (note 1). Flowers appear to be mostly self-pollinated in Northern Ireland but in some places (such as on Svalbard) they are visited by insects.

Sometimes the plant occurs as a casual for just a few years before being washed away by storms but colonies can persist for hundreds of years when conditions are right. (Plants growing in pure sand are usually short-lived.)

Mertensia maritima is very much a plant of northern areas. In the British Isles it can now be found in Scotland (especially Orkney and Shetland) and Northern Ireland. In Northern Ireland it is on a list of Priority Species;  the plant also features in a 1992 article in the Irish Naturalists’ Journal. There are pre-2000 records from Northern England, North Wales and the Isle of Man, but the plant is contracting its range in the south and expanding its range further north. Further afield, the plant grows in Svalbard, Franz Joseph Land, Iceland, Greenland, North-east Asia and North America, including Canada and, in the United States, New England (note 2). Its southern limit more or less corresponds with the mean January isotherm of 4.5 °C and the mean July isotherm of 19 °C.

With its northern distribution, Mertensia maritima may well be adversely affected by climate change (note 3). The Online Atlas of the British Flora gives storms, recreational pressures, shingle removal and grazing as reasons for losses. Like the Sea Pea (Lathyrus japonicus) that I wrote about in August 2017, visitor pressure may be very significant.

Here are some examples of the threats to Oysterplant:

I’ve only seen Oysterplant twice and in both cases the location of the plants made my memories stronger.

I first saw the plant in 1997 on a a three week cycling trip in Iceland. While we were camping in Reykjavik we walked down to the harbour to look at the Sun Voyager. The sculpture was lovely and so was the Oysterplant growing on the shoreline nearby.

The second sighting was on another cycling trip, this time in 2006, on Orkney. We were camping in Kirkwall and decided to visit South Ronaldsay for the day. Cycling south to the Tomb of the Eagles at the far end of the island we crossed the Churchill Barriers (note 4).  Oysterplant was growing in a sandy area next to one of the Barriers.

The leaves of Mertensia maritima are edible, both raw and cooked, as are the flowers and root, but the plant is so uncommon that I don’t recommend picking it from the wild. The name “Oysterplant” comes from the taste of its leaves.

Several plants are described as “tasting like oysters”, including Salsify, which I have written about, and its close relative Scorzonera, but I’m not too convinced about the similarity.

The Plants for a Future website has a similar opinion of Oysterplant. “No-one has yet noticed a resemblance to oysters though not many of the tasters have ever eaten oysters! The flavour is fairly bland, the leaf is thick and has a very mucilaginous texture – it is probably this texture that reminds people of oysters.” I’ve eaten and enjoyed oysters a few times. It is the texture, combined with a fresh sea water saltiness, that defines the experience for me, rather than any strong taste.

But in “Flora Britannica”, Richard Mabey quotes a man in Scotland who has Oysterplant growing on his local beach. “I was once poisoned by an oyster and I can’t abide them. The taste of the leaf made me retch, so true is it to its name” (note 5).

The Edible Wild Food website says that “leaves can be added to salads, and they go quite well with eggs”. The Edible Garden Nursery website suggests that the leaves can be used “in fish dishes or salads.”

Oysterplant is often difficult to cultivate and is very susceptible to slug damage. Plants don’t like root disturbance and are most likely to succeed in well-drained sandy or gravelly soils in a sunny position. I haven’t tried growing it and I suspect it would be too hot for it here in Norfolk. However, if you like a challenge, why not give it a try? If you live in the UK, plants are available (to pre-order) from The Edible Garden Nursery. The Dave’s Garden website lists people in America and Europe who may be able to supply the plant. Oysterplant can also be grown from seed.

Other English names for Oysterplant include Seaside Bluebells, Sea Lungwort and Gray Oysterleaf.

Mertensia is named after the German botanist Franz Carl Mertens (1764 – 1831). The genus also includes American species such as Mertensia ciliata  (Fringed Bluebells) and and Mertensia virginica (Virginia Bluebells).

Notes

Note 1: The germination rate of seeds is increased improved by exposure to temperatures of 2°C or below. The British Wild Plants site is understandably gloomy about the plant’s return to Wales: “… the … seeds … must have a prolonged period in the cold sea water below 5C and then some time on cold pebbly beach in order to scrape the hard outer coat of the nutlets and allow germination to begin. The winter seas around Wales are far too warm now and it will probably never return.”

Note 2: The Flora of Svalbard describes three subspecies of Mertensia maritima. These are ssp. maritima, ssp. tenella and ssp. asiatica. Mertensia martima in the British Isles and New England is ssp. maritima, while ssp. tenella occurs in Svalbard. (I have been to Svalbard but annoyingly, I can’t remember seeing Oysterplant – I think I would have remembered if I had.)  Ssp. asiatica is found by the Pacific Ocean.

Note 3: Mertensia maritima is specfically mentioned in the MCCIP report “Impacts of climate change on coastal habitats” – L. Jones, A. Garbutt, J. Hansom and S. Angus (2013), MCCIP Science Review 2013: pp167-179. Climate change may lead to more storm surges, increases in temperatures and changes to rainfall (see page 172 of the report).

Note 4: The Churchill Barriers were built in the Second World War to protect Scapa Flow from enemy submarines and ships. They are now used as causeways to provide a road link from South Ronaldsay to Orkney’s Mainland, via Lamb Holm, Glimps Holm and Burray.

Note 5:  Richard Mabey (1996): “Flora Britannica“, Sinclair-Stevenson, London. Page 310.

Red Valerian, Centranthus ruber

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Red Valerian with Small Tortoiseshell

Small Tortoiseshell butterfly on Red Valerian

New Year started well, with sightings of three Otters on our local stretch of river and four Waxwings by our local church, just visible from the kitchen window. But it’s rather cold today and definitely time for another blog post.

At this time of year, there are two choices: write about something seasonal (like Winter Heliotrope, Mistletoe or Ivy) or escape to memories of summers past. I’ve chosen the latter and today I’m writing about Red Valerian (Centranthus ruber).

Red Valerian comes from the Mediterranean area: the Azores, southern Europe and North Africa. It is a native in parts of Albania, Algeria, The Azores, Balearic islands, Corsica, France, Greece, Italy, Morocco, Portugal, Sicily, Spain, Tunisia, European Turkey and the former Yugoslavia. It has been introduced into many other countries, including New Zealand, parts of the United States (including California and by the Puget Sound in Washington) and in the United Kingdom and Ireland. In South Africa it is classed as an invasive plant, and may not be owned, imported into South Africa, grown, moved, sold, given as a gift or dumped in a waterway.

In the British Isles Red Valerian is a neophyte and was being grown as a garden plant by 1597. It was first recorded in the wild in Cambridgeshire in 1763 and is now thoroughly naturalised in lowland areas. It is frequently found in well drained, disturbed areas such as sea cliffs, limestone rock outcrops and pavements, rocky waste ground, in quarries, on railway banks, on old walls and on buildings. In most of England and Ireland Red Valerian grows inland as well as on the coast, but in Scotland it is more of a coastal plant. There are records as far north as Shetland. The plant is given a hardiness rating of H5 by the Royal Horticultural Society (RHS) – hardy in most places throughout the UK even in severe winters (-15C to -10C). I have fond memories of Red Valerian growing on south-facing cliffs on the Isle of Wight, in shingle at Dungeness (Kent) and Shingle Street (Suffolk) and, as a child, on the North Wales coast.

There are about twelve species of Centranthus and they form part of the Caprifoliaceae (Honeysuckle family). Centranthus ruber can grow as a hardy perennial or a short woody plant (subshrub). We grow it in our front garden, where it dies back in the winter and so behaves more like a hardy perennial. The grey-green leaves grow in opposite pairs and the spurred flowers, which have five petals, grow in clusters on stems up to about a metre (nearly three feet) tall.

It is not surprising that Red Valerian is very popular garden plant. It thrives in sun but will tolerate some shade too. The flowers come in at least three different colours, including pink (the commonest form), white (form ‘Albus’, which is off-white with a pinkish tinge, and ‘Snowcloud’, which has the purest white flowers) and red (form ‘Coccineus‘, which is deep red, and ‘Atrococcineus‘, which is a darker carmine-red) (note 1). I grow the pink form and ‘Albus’. The former grows rampantly but ‘Albus’ seems less vigorous. The plants flower here in Norfolk from May throughout the summer until September or October. In milder areas such as Cornwall they can be in flower at Christmas. The First Nature website has some lovely pictures of the flowers, including close-ups and different colour forms. If you want to propagate a particular colour form, you will need to take cuttings. The flowers can have a distinctive scent, usually described as ‘somewhat rank‘. The Scottish Rock Garden Club Forum has an interesting discussion about the scent and different colour forms.

Red Valerian produces masses of tufted seeds that are dispersed by the smallest of air movements. In our garden, Red Valerian is gradually spreading to the back garden. We don’t really mind, but the plant definitely has the capacity to become a “weed” for some gardeners and the RHS website has advice for growing Red Valerian, as does Gardening Know How, while the Gardeners’ World website has advice if it becomes a problem. The plant has deep roots, which allow it to grow in dry places but can sometimes cause damage to walls. If you cut the dying flowers back you will reduce the amount of self-seeding and prolong the flowering period.

So far I’ve used the name ‘Red Valerian’ for Centranthus ruber, but like many plants there are lots of alternatives and other English names include Jupiter’s Beard, Drunkards and Sweet Betsy (note 2), Keys of Heaven (note 1), Spur Valerian, Kiss-me-quick, Fox’s Brush and Devil’s Beard. The latter presumably comes from the seed heads. The name Centranthus  comes from the Greek words kentron (a spur) and anthos (a flower); ruber means red.

I haven’t tried eating our Red Valerian but the young leaves are edible raw or cooked and can be used in soups. The roots can also be cooked.  Margaret Grieve (note 3) thought that the leaves were “exceedingly good, either in salads or cooked as a vegetable”, but the authors of the Plants For A Future website aren’t so sure: “This differs from our own experience, whilst the leaves can be added to salads they are rather bitter and rather less than desirable”. Richard Mabey says that the very young leaves are sometimes boiled with butter as greens or eaten raw in salads in France and Italy (note 4). According to The Urban Veg Patch website, Mark Diacono “reckons that the leaves have a taste reminiscent of broad beans” (note 5). It is possibly a taste that needs to be acquired.

Medicinally, the Paghat’s Garden website says that “the flowers, young shoots, roots and soft young leaves [of Red Valerian] are a folk remedy for cold, flu, or cough, even though almost certainly ineffective”. The Plants For A Future website agrees that Red Valerian “has no known medical properties“. Apparently Red Valerian seeds were sometimes used in embalming.

Red Valerian is a good plant for insects, including butterflies and bees. As well as the Small Tortoiseshell featured at the top of this blog post, I have photographed Clouded Yellow, Glanville Fritillary and Painted Lady butterflies on the flowers – at Shingle Street, on the Isle of Wight and in our garden respectively. I’ve also seen the flowers uses as a source of nectar for Anthophora quadrimaculata (the Four-banded Flower Bee) in our garden and, in 2018, by St. Giles’ Church in the centre of Norwich (although Catmint is more popular). The Humming-bird Hawkmoth loves the flowers and other moths such as the Angle Shades will feed on the leaves.

This spring, sharp-eyed James Emerson visited our garden and spotted leaf-roll galls on our Red Valerian plants. The galls are formed by the psyllid (jumping plant louse), Trioza centranthi. This insect was a historically rare and scattered species but it seems to be spreading and there have now been several records in Norfolk. Later in the season the galls become more obvious, especially on pink and red-flowered plants, where they stand out from the rest of the leaf (note 6). I’m pretty certain that 2018 is their first year in our garden.

Trioza centranthi leaf-roll gall on a Red Valerian leaf (early May 2018).

Notes

Note 1: The name ‘Keys of Heaven’ and descriptions of colour forms come from the “RHS Encyclopedia of Perennials” (2011; Editor-in-chief Graham Rice, Dorling Kindersley, London).

Note 2: Richard Mabey (1996): “Flora Britannica“, Sinclair-Stevenson, London. Page 350. ‘Drunkards’ probably comes from the plant’s habit of nodding tipsily in the wind.

Note 3: Margaret Grieve (1931), “A Modern Herbal“. Reprinted in 1996 by Barnes and Noble / Random House. Quoted on the Plants For A Future website.

Note 4: Richard Mabey (1975), “Food For Free”, Fontana, Glasgow. Page 106.

Note 5: Mark Diacono (2015) “The New Kitchen Garden“, Hodder and Stoughton.

Note 6: When I wrote this on 3rd January 2019 I hadn’t seen the galls on white-flowered Centranthus ruber plants, but had been told that when they occur they are apparently green like the rest of the leaf, rather than pink. (This would make sense as the white-flowered plants presumably have a block in the biochemical pathway for the synthesis of anthocyanins, which give the pink and red flowers their colours.) On 4th January I found a gall on a white-flowered plant and it had no obvious red pigment.

The “British Plant Galls” Facebook group has just started a citizen science ‘Trioza centranthi gall colour project’ to investigate the correlation between flower and gall colour. If you join the group, you can take part in it.

Hemlock Water Dropwort, Oenanthe crocata

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Hemlock Water Dropwort, Oenanthe crocata

Hemlock Water Dropwort, Oenanthe crocata. In flower, Isle of Wight, mid May 2016.

Fancy a curry? I do, and I like foraging for food, but I won’t be using Hemlock Water Dropwort, Oenanthe crocata. Here is a cautionary tale.

About twenty years ago a group of eight young adults on holiday in Western Scotland found what they thought were Water Parsnips growing in a small stream. They picked them and added them to a curry (note 1).

By the next morning, one person, who had eaten more than the rest, was having seizures and other members of the group felt unwell and nauseous. In spite of this, four people ate the leftover curry for lunch and one of this group also had a seizure. Fortunately the police were able to take one of the group back to the stream to collect a sample of the plant, which was identified by a local botanist and following treatment in the local hospital all of the group recovered (note 2).

Hemlock Water Dropwort, Oenanthe crocata, is a fast growing perennial plant of wetlands, streams, ditches and the margins of rivers. It is a member of the Apiaceae (Parsley family) and its flowers are arranged in the family’s characteristic umbels. I have previously written about several members of this family, most recently Wild Carrot (Daucus carota).

There are eight species of Water Dropwort (Oenanthe) in the British Isles, all of which are poisonous. Oenanthe crocata is found mainly in the south and west, including Scotland and Ireland, mainly in lowland areas (note 3). Its stems elongate in spring and it flowers from May to July, depending on location. In 2016 it was flowering on the Isle of Wight in mid May, while in the Oban area in May 2018 the plant was in leaf or in bud. There are some excellent close-up photographs of the plant at different stages of growth on the internet, including the Wildflower Finder and First Nature websites.

It is well worth being able to identify Oenanthe crocata as it is probably “the most toxic plant in Britain to both humans and animals“. Its leaves look lush and tempting and remind me of Flat-leaved Parsley, Petroselinum crispum var. neapolitanum, which I grow on my allotment. Both plants have smooth, hairless stems and leaves and Hemlock Water Dropwort’s leaves have a similar smell to parsley but Flat-leaved Parsley never grows in wet ditches. The lush growth and smell are also a bit like Wild Celery, Apium graveolens, which also grows on wet ground but mostly in the south.

“Oenanthe” is derived from the Greek words oinos “wine” and anthos “flower”, from the wine-like scent of the flowers (note 4). “Dropwort” comes from the (slight) resemblance of some smaller species of Oenanthe to Dropwort, Filipendula vulgaris, which grows in dry grassland and whose root tubers hang like drops from its roots.

All parts of Hemlock Water Dropwort are toxic to mammals. Cattle can eat small quantities of the leaves with no ill effect, but not the plant’s white, fleshy tubers, which are the most toxic part of the plant. They are normally hidden below ground but may be exposed by poaching by cattle, or by flooding or enthusiastic curry-eating foragers. The level of toxins is highest in late winter and early spring, when the plant’s foliage has died down. The tubers are sometimes known as “Dead Mans Fingers” as they typically occur in groups of five or more. They exude a yellowish liquid when cut, which stains the skin.

The main poisonous substance in Hemlock Water Dropwort is a polyunsaturated higher alcohol called Oenanthotoxin. Its direct effects are on the central nervous system, which results in a large number of unpleasant effects, listed here. They range from slurred speech, dizziness and nausea to spasms, acute renal failure and cardiac arrest. The Wildflower Finder website gives more details of the plant’s biochemistry. Research has also been carried out on the plant’s essential oil’s antifungal, antioxidant and anti-inflammatory properties (note 5).

As well as a knowledge of Botany, a knowledge of History comes in handy when you’re sourcing ingredients for a curry. There have been at least fourteen cases of Hemlock Water Dropwort poisoning in the UK in the 20th Century. The Poison Garden website lists a number of cases of poisoning, ranging from a mild (but nonetheless unpleasant) case of poisoning by eating the leaves to stories from the 1970s and 1980s and as far back as the Napoleonic Wars. The latter incident involved eleven French prisoners in Pembrokeshire, two of whom died. John Robertson, the author of the Poison Garden website gives more details in his excellent book “Is that Cat Dead?” (note 6).

One of the symptoms of Oenanthotoxin poisoning is a spasm of the facial muscles known as a sardonic grin (risus sardonicus), although a sardonic grin may also be caused by tetanus, strychnine poisoning or Wilson’s disease. In Sardinia in the pre-Roman Nuragic culture, a “sardonic herb” creating this spasm was used for the ritual killing of elderly people. Italian scientists have suggested that the herb may have been the close relative Oenanthe fistulosa. (O. fistulosa is known as Tubular Water Dropwort in Britain.) (note 7).

Oenanthotoxin is thought to be absorbed through the skin, so try not to splash yourself with the plant’s sap. Artists should heed the warning from  the German eighteenth century botanical illustrator Georg Ehret, who found that Hemlock Water Dropwort made him giddy when he was drawing it in an enclosed room. Fortunately his solution – to open the windows to allow fresh air to circulate – was completely successful (note 8).

Although Hemlock Water Dropwort is poisonous to mammals, its flowers are attractive to insects, including Marsh Fritillary butterflies, as photographed by Ray Cannon in Galicia in north-west Spain. My friend Stuart, based in Cornwall where Hemlock Water Dropwort is abundant, tells me that beetles (including flower, longhorn and soldier beetles) and flies (including hoverflies) are especially fond of the flowers.

Hemlock Water Dropwort leaves

Hemlock Water Dropwort leaves, looking rather like Flat-leaved Parsley. Near Oban, mid May 2018.

Notes

Note 1: It does make you wonder why they thought this was a good idea. There are two British plants commonly known as “Water Parsnip”, both of which grow by and in fresh water. Berula erecta, Lesser Water Parsnip, is the most widespread and reaches the south of Scotland and Sium latifolium, Great Water Parsnip, is a scarcer Fenland plant. Both are poisonous, although Sium latifolium leaves have been cooked in Italy and its seeds have been used in small quantities as a spice in Scandinavia. The roots are sometimes compared to “white carrots” but apart from the fact that they grow undergound, they don’t look similar to me.

Note 2: Downs C, Phillips J, Ranger A, et al (2002). “A hemlock water dropwort curry: a case of multiple poisoning”. Emergency Medicine Journal  Vol. 19: pp 472-473. The article is available online and makes an interesting read.

Note 3: Oenanthe crocata also grows elsewhere in Europe. It has also recently been recorded in the Buenos Aires area of Argentina as an introduced plant.

Note 4: Not to be confused with the bird with the same generic name, the (Northern) Wheatear, Oenanthe oenanthe. The bird is called Oenanthe because the birds return to Greece in the spring just as grape vines are in blossom.

Note 5: Valente, Júlia & Zuzarte, Mónica & Gonçalves, Maria & Lopes, Mc & Cavaleiro, Carlos & Salgueiro, Ligia & Cruz, Mt. (2013). “Antifungal, antioxidant and anti-inflammatory activities of Oenanthe crocata L. essential oil.” Food and Chemical Toxicology  Vol. 62.

Note 6: John Robertson (2010), “‘Is That Cat Dead?’ and other questions about poison plants”. Book Guild Publishing, Sussex, England. The book is now quite hard to find.

Note 7: Giovanni Appendino, Federica Pollastro, Luisella Verotta, Mauro Ballero, Adriana Romano, Paulina Wyrembek, Katarzyna Szczuraszek, Jerzy W. Mozrzymas, Orazio Taglialatela-Scafati (2009). “Polyacetylenes from Sardinian Oenanthe fistulosa: A Molecular Clue to risus sardonicus“, J. Nat Prod. Vol. 72(5): pp 962–965.

Note 8: Richard Mabey (1996): “Flora Britannica“, Sinclair-Stevenson, London. Page 289.