Dodder, Cuscuta epithymum

Jeremy Bartlett's LET IT GROW blog Posted on by

“The wonder of the world
The beauty and the power
The shapes of things,
Their colours, light and shades
These I saw,
Look ye also while life lasts.” (note 1).

Common Dodder, Cuscuta epithymum

Common Dodder, Cuscuta epithymum. Bryant’s Heath, Norfolk, mid July 2021. (The purple in the background is Bell Heather, Erica cinerea.)

My Favourite Vampire

For some people it’s Dracula, but my favourite vampire is Common Dodder, Cuscuta epithymum. It is always a pleasure to see it, with its stems twining like pink spaghetti or silly string over gorse and Heather.

Cuscuta epithymum is a member of the Convolvulaceae (Bindweed family) and twines its stems over vegetation like its leafy green relatives Field Bindweed (Convolvulus arvensis) and Hedge Bindweed (Calystegia sepium). But Dodder is a parasitic plant with much smaller flowers and small, scale-like leaves. It lacks chlorophyll and depends on its host plant for its supply of nutrients (note 2).

In Norfolk, Common Dodder grows on sandy, acid heaths, including Kelling Heath, Buxton Heath, Holt Lowes and Bryant’s Heath and parts of Beeston Common. Here, it sprawls low over the ground, but at Incleborough Hill, near West Runton, Dodder it grows to a massive size as it clambers over Common Gorse bushes.

In Norfolk Common Dodder’s hosts are gorse (Common Gorse, Ulex europaeus and Western Gorse Ulex galii) and Ling (Calluna vulgaris) and these are the commonest host plants, according to Stace (note 3). But Cuscuta epithymum will parasitise a wide range of plants, including Common Hawthorn and especially clovers (Trifolium sp.) and other members of the Pea family (Fabaceae) such as Dyer’s Greenweed (Genista tinctoria). It is sometimes called Clover Dodder or Alfalfa Dodder because of its host plants. In the British Isles Cuscuta epithymum sometimes parasitises Wild Thyme (Thymus polytrichus) and in southern Europe it grows on Conehead Thyme (Thymus capitatus), where it apparently takes on the pungent smell of is host. Its specific name, epithymum, comes from growing on thyme.

In the British Isles Common Dodder is most abundant in the south of England but occurs as far north as Fife in Scotland and in parts of Wales and Ireland. As well as heathland, it grows on chalk downland and fixed dune grasslands and sometimes as a casual on field crops and in arable field-borders at the northern and western limits of its range. Dodder has declined since the 1930s as its habitats have been lost, through ploughing of downland and increase in scrub and the destruction of lowland heaths through forestry and house building.

Dodder flowers

Common Dodder flowers

Common Dodder flowers from July to September in the British Isles, but much earlier in southern Europe. (The First Nature website has photographs of the plant flowering in early April in Crete.) The flowers can be pollinated by insects or self-pollinated. Dodder flowers sometimes smell of rotting fish (perhaps to attract Blowflies as pollinators). In contrast, the Plants For a Future website refers to the “remarkably sweet perfume” of the flowers, which is “especially pronounced towards evening“. I sniff the flowers whenever I remember to, but I’ve never noticed much scent (but see update July 2023).

Common Dodder is a native of Europe, West Asia and northern Africa but has also been introduced into North America, South America, Japan, Australia and New Zealand. It is also found in parts of eastern and southern Africa, either as a native or introduction. Across its range there are at least two subspecies and, within these, several varieties. These are distinguished by differences in their flower structure as well as the number of flowers and how they are grouped.

Common Dodder can grow as an annual or perennial plant.

It has small seeds (about 1 millimetre in diameter) and these can lie dormant for years. But seeds cannot live ever and if an area of heathland remains unmanaged for a long period of time Dodder may be unable to survive.

If the conditions are suitable Dodder seeds will germinate as the weather warms up in spring (from April onwards). When the seed germinates, a swollen, root-like organ emerges from the seed case and seeks out a suitable host (note 4). At this stage the plant is using nutrients stored in its seed and it must find a host plant quickly or it will die.

Once a host is found, Dodder attaches to it with a sucker and forms a haustorium (a structure that penetrates the host’s tissue and draws in nutrients; see my post on Mistletoe). The root-like organ withers and from this point onwards nutrients are taken from the host plant through the haustorium and the Dodder starts to grow very rapidly, twining anti-clockwise around its host (as does bindweed, note 5). It is vital that the plant stays attached to its host and the Dodder produces a kind of glue to ensure this happens.

Common Dodder can also grow as a perennial by forming an overwintering gall within a stem of its woody host. In autumn the twisting stems die back but the Dodder survives and produces new growth in the spring. This strategy removes the risk of not being able to find a host (note 6).

Gerald Durrell refers to Common Dodder in his book “The Amateur Naturalist” (note 7). It’s a moment of high drama: “In the heath communities of the south you can find the innocent-looking common dodder. This has no leaves but a hard red stem and clusters of delicately-shaped pink flowers. But don’t be misled by its appearance, for it is a sort of plant Dracula. It climbs up its victim anticlockwise and the roots from its wiry stem pierce the flesh of its host and suck out the nutrients. In some cases the dodder, like Dracula, leaves its victim dead, drained dry.”

Dodder can undoubtably affect the vigour of its host plant but killing the host is not in a parasite’s best interests and growth is usually dependant on the vigour of the host plant.

The Plants for a Future website gives a number of medicinal uses for Dodder, including problems with the liver and gall bladder, urinary complaints and gout. It warns that the plant should not be used by anyone suffering from haemorrhoids. During medieval times, Dodder was used as a cure for depression, but its consumption apparently causes thirst and dryness of the mouth.

My most recent sighting of Common Dodder was at Bryant’s Heath, near Felmingham in North Norfolk. Most of the Dodder was the usual pink colour, but some of the plants were yellow.

Common Dodder with yellow stems and flowers.

Common Dodder with yellow stems and flowers. (You can see some pink strands as well.)

The pink in wild type Common Dodder stems is due to the presence of anthocyanins (cyanidin glycosides) (note 8). The yellow plants must have a block in the anthocyanin biosynthetic pathway. Stace (note 3) mentions these occasional variants: “stems reddish except yellowish in rare albinos”.

A quite separate plant is Yellow Dodder, Cuscuta campestris. This is a North American plant that is sometimes accidentally introduced to fields (where Carrot is one of its hosts) or in bird food mixes. I saw it growing at Natural Surroundings in North Norfolk a few years ago and it persisted in a friend’s garden on the outskirts of Norwich for several years.

The third species of Cuscuta in the British Isles is Greater Dodder, Cuscuta europaea, which usually grows on Stinging Nettles (Urtica dioica), often near water. It is rare and I have yet to see it.

Mike Crewe’s Flora of East Anglia website has some good pictures of all three species on one page for easy comparison.

Notes

Note 1 – I love this quote. It originally comes from a Cumbrian gravestone. It was used by the naturalist, illustrator and author BB (Denys Watkins-Pitchford) in his preface to “Down the Bright Stream”, the second of his books about the last four gnomes in Britain (the first is “The Little Grey Men“). The gnomes are led by Dodder, the oldest and grumpiest gnome, and this provides my feeble excuse for including it here.

Note 2 – Other completely parasitic plants I’ve written about include Ivy Broomrape, Purple Broomrape and Purple Toothwort.

Note 3 – Clive Stace, “New Flora of the British Isles“, pages 603 – 604. (Fourth Edition, 2019.)

Note 4 – Common Dodder “sniffs out its hosts, by recognising their chemical signature”. https://www.nationaltrust.org.uk/west-runton-and-beeston-regis-heath/features/the-amazing-world-of-dodder-cuscuta-epithymum.

There are some good – and a bit creepy – videos of various species of dodder on You Tube, such as https://www.youtube.com/watch?v=5gPuXtmrP0E.

Note 5 – As mentioned in the Flanders and Swann song “Misalliance”, on their album “At The Drop of a Hat”, although the song is really a commentary on politics and class rather than Botany.

“The fragrant honeysuckle spirals clockwise to the sun,
And many other creepers do the same.
But some climb anti-clockwise, the bindweed does, for one,
Or Convolvulus, to give her proper name.” – Flanders & Swann.

You can listen to the song on You Tube at https://www.youtube.com/watch?v=WhJ1MDfvix4.

Note 6 – The information in the previous four paragraphs mainly comes from the Kew Gardens website, http://powo.science.kew.org/taxon/267419-1. The direct contact between species of Cuscuta and their hosts is one of the reasons why Cuscuta species are the most rapidly growing parasitic plants.

Note 7 – Gerald Durrell with Lee Durrell, “The Amateur Naturalist”, Dorling Kindersley (1982), page 72.

Note 8 – See page 121 in the 1941 paper by Beale, Price & Sturgess, “A survey of Anthocyanins VII. The natural selection of flower colour”,  https://royalsocietypublishing.org/doi/pdf/10.1098/rspb.1941.0008.

Update July 2023

On 20th July 2023 I visited Buxton Heath and had another sniff of Dodder. This time the flowers had a distinct not very pleasant scent that combined sweetness and decay.

There were no Blowflies but the flowers were attracting Bee-wolves (Philanthus triangulum). These large, impressive wasps are now common in southern England, having spread rapidly since the 1990s. We now have them visiting our garden (they love Echinops flowers) and they nest on road verges in Norwich. Females catch worker Honeybees to stock their nest holes and feed their larvae.

Bee-wolf on Dodder flowers

Bee-wolf (Philanthus triangulum) on Dodder flowers. Buxton Heath, 20th July 2023.

Common Cow-wheat, Melampyrum pratense

Jeremy Bartlett's LET IT GROW blog Posted on by

On Tuesday Vanna & I visited West Blean & Thornden Woods in Kent, a lovely ancient woodland nature reserve managed by Kent Wildlife Trust. We were on the hunt for the Heath Fritillary butterfly, Melitaea athalia, a rare butterfly in Britain. We saw our first Heath Fritillaries in France, on a holiday in the Vendée in May 1990, but wanted to see them again, and in Britain, hence our trip to Kent.

The main food-plant of the Heath Fritillary’s caterpillars is Common Cow-wheat, Melampyrum pratense (note 1).

Common Cow-wheat, Melampyrum pratense

A patch of Common Cow-wheat, Melampyrum pratense in West Blean & Thornden Woods, Kent, June 2021.

Common Cow-wheat, Melampyrum pratense, is a close relative of the showier and much rarer Field Cow-wheat, Melampyrum arvense, that I wrote about in May 2019 after a visit to the Isle of Wight.  It is a member of the family Orobanchaceae and is an annual hemi-parasite: it possesses chlorophyll and makes its own sugars but it also takes some of its nutrients from its host plants (note 2).

Common Cow-wheat is widely distributed in the British Isles (see map), though here in Norfolk it is not particularly common. “A Flora of Norfolk” (1999) says it is found in five sites in the county, a decline from a pre-1978 total of nine sites. Fortunately my nearest colonies (not mapped in the 1999 Flora) are in Norwich, just a short walk from home, in Bluebell Wood, at the west end of Eaton Park.

Common Cow-wheat flowers from May to September, peaking in June or July. It can often carpet the ground where it grows. It was abundant in the woods near Watendlath in the Lake District which we visited in June 2019 and there were large patches of it in West Blean & Thornden Woods, though only patches in open sunny parts of the woods are suitable for Heath Fritillaries.

Melampyrum pratense has two sub-species in the British Isles: pratense and commutatum. The commoner subspecies, pratense, grows in woods, scrub, heaths and moors on well-drained, nutrient-poor acidic soils. Less commonly, subspecies commutatum grows on chalk and limestone, in scrub, hedgerows and deciduous woodland. The Wildflower Finder website has lots of excellent photographs and more details of both subspecies (note 3).

Once it has flowered, Common Cow-wheat sets seed and these are attached to a fleshy structure known as an elaiosome. This is rich in lipids  and proteins and highly attractive to ants, which aid seed dispersal. Seed set and dispersal is vital as Common Cow-wheat is an annual and must reproduce by seed each year. Fortunately self-pollination will allow the plants to set seed when suitable pollinating insects are scarce. Seeds germinate in late autumn or early winter and put on a spurt of growth in spring.

Like Field Cow-wheat, Common Cow-wheat contains aucubin, an iridoid glycoside and high concentrations are found in the seeds. This is slightly toxic and probably makes the plants less attractive to herbivores.

Common Cow-wheat, Melampyrum pratense

Common Cow-wheat, Melampyrum pratense. Near Watendlath, Cumbria, June 2019.

Not all stories have a happy ending but ours did.

We found our Heath Fritillaries, which were just as delightful as the ones we saw in France over thirty years ago. On both occasions we travelled with our friends Steve & Janice, who I’d like to thank for letting us see this butterfly (and its foodplant) once again.

Common Cow-wheat, Melampyrum pratense, and Heath Fritillary

Common Cow-wheat, Melampyrum pratense, with a Heath Fritillary. West Blean & Thornden Woods, Kent, June 2021

Heath Fritillaries

Heath Fritillaries, West Blean & Thornden Woods, Kent. June 2021.

Notes

Note 1 – Heath Fritillary caterpillars will also feed on Ribwort Plantain (Plantago lanceolata), Germander Speedwell (Veronica chamaedrys), and occasionally other speedwells (Veronica spp.). Foxglove (Digitalis purpurea) can be a secondary foodplant, especially on Exmoor. The butterfly also occurs in woods in Devon and Cornwall, on Exmoor and (as a result of re-introductions) in Essex.

Note 2 – Common Cow-wheat seems to parasitise woody plants but there seems to be some doubt as to which ones.

The NatureGate website mentions Pine and Cowberry as hosts in Finland.

A 1963 paper, “Variation in Melanpyrum pratense” by A. J. E. Smith (Watsonia Vol 5(6), pp 336 – 367) suggests Ling (Calluna vulgaris), heaths (Erica) and Bog Myrtle (Myrica gale) as major hosts in Britain, as well as other plants such as Beech (Fagus sylvatica), Rowan (Sorbus aucuparia) and Sessile Oak (Quercus petraea).

But in his paper “Transplanting and sowing seed of common cow-wheat Melampyrum pratense to increase its distribution at Blean Woods RSPB Reserve, Kent, England” (Conservation Evidence (2005) vol 2, pp 41-42) Michael Walter concludes that “the principal host and the host-plant(s) remains at Blean a mystery”.

Note 3 – Another difference is that the uppermost leaves (below the bracts) are 7 to 15 times longer than wide in ssp. pratense and only 3-8 times longer than wide in ssp. commutatum.

Subspecies pratense has rich yellow flowers and grows on acidic soils whereas commutatum has pale yellow flowers and grows on alkaline calcareous soils, mainly in the south.

See the Wildflower Finder website and Clive Stace’s Flora for more information.

White Dead-nettle, Lamium album

Jeremy Bartlett's LET IT GROW blog Posted on by
White Deadnettle, Lamium album

White Dead-nettle, Lamium album

One of the highlights of this cold, late spring has been the profusion of Dead-nettle flowers, first Red (Lamium purpureum) and now White (Lamium album). These may just be common wild flowers – weeds to the less enlightened – but they raise my spirits nonetheless.

I wrote about the Red Dead-nettle back in 2012. The White Dead-nettle, Lamium album, is its perennial cousin: in the same genus (Lamium) and family (Lamiaceae (Note 1)). The Red Dead-nettle is an annual; White Dead-nettle is a hardy perennial which stays green over winter and spreads by seed and by its rhizomatous stolons (rooting stems that run horizontally underground).

The White Dead-nettle is very common in the British Isles, apart from the far north and west of Scotland and western Ireland. It grows in secondary woodland, on hedge-banks and roadsides and disturbed ground, including on the rougher edges of my allotment. Plantlife give it a status of “Green – Least concern”.

White Dead-nettles often grow near human habitation, in the same fertile soils as the Stinging Nettle (Urtica dioica). Although they often grow amongst Stinging Nettles and their leaves have a similar shape to Stinging Nettle leaves, White Dead-nettles have lighter green, softer leaves, square stems, a distinctive smell and, crucially, whorls of white flowers with hairy upper hoods and toothed lower lips (note 2). Flowers are produced from March until as late as December, peaking in April and May. The flowers’ anthers are a beautiful black and gold but you have to peer into the flower to see them. They lie side by side like two human figures, Adam and Eve, hence the plant’s alternative name of Adam-and-Eve-in-the-bower. Other English names include Helmet-flower (from the flower shape), Blind Nettle, Dumb Nettle and Deaf Nettle (because of the lack of stings) and White Archangel (note 3).

Lamium album grows right across Eurasia as far east as Japan. The European subspecies is subspecies album and subspecies barbatum is found in the far east of mainland Asia and in Japan. In the British Isles it is considered to be an archaeophyte (introduced by humans prior to 1500).  The BSBI classes it as a denizen: “having the appearance of being native (i.e. fully naturalised) but with some suspicion of having been originally introduced“. It has been introduced to the United States, where it is widely naturalised.

The White Dead-nettle is a good wildlife plant. It is sometimes known as the Bee Nettle as its flowers attract heavier, larger bees, especially Bombus pascuroum, the Common Carder Bee. Hairy-footed Flower Bees (Anthophora plumipes) also visit to collect both pollen (females only) and nectar.

Bombus pascuorum

Male Bombus pascuorum on White Dead-nettle. Photo credit: Vanna Bartlett.

Anthophora plumipes female

A female Hairy-footed Flower Bee, Anthophora plumipes, visiting White Dead-nettle. Photo credit: Vanna Bartlett.

If you live in southern Britain have a look out for the attractive Pied Shieldbug, Tritomegas bicolor, which feeds at the base and on the aerial parts of the plant. We often find it in large numbers of it on our allotment in spring, on Black Horehound (Ballota nigra) and on Red Dead-nettles as well as White.

Pied Shieldbug

Pied Shieldbug, Tritomegas bicolor, on White Dead-nettle. Photo credit: Vanna Bartlett.

The Green Tortoise Beetle, Cassida viridis, also feeds on White Dead-nettle and its relatives, as do the caterpillars of several species of moths, including the Burnished Brass and Speckled Yellow. (The “Field Guide to the Caterpillars of Great Britain and Ireland” lists fifteen species of moth whose foodplant is White Deadnettle.)

The leaves and flowers White Dead-nettles are edible and pleasant – don’t be put off by the hairiness of the leaves. I sometimes add a few young leaves to a mixed salad, or nibble at a leaf when I visit the allotment, but there are a lot more possibilities.

Young leaves and stem tips can be boiled and eaten as a vegetable, and the leaves can be cooked like spinach or chopped and added to omelettes. Flowers can be candied or used to make wine. The Eatweeds website has recipes for a White Dead-nettle Frittata and a White Dead-nettle, Feta and Watermelon Salad. The Plants for a Future website recommends adding the leaves to salads and says that “a pleasant herb tea is made from the flowers“. The leaves contain good quantities of vitamins A and C, calcium and phosphorus.

The herbalist Nicholas Culpeper (1616 – 1654) thought that the White Dead-nettle “makes the head merry, drives away melancholy, quickens the spirits, is good against quartan agues, stancheth bleeding at the mouth and nose.” (You can read his full description on The Complete Herbal website.)

The Eatweeds website and Plants For A Future list a number of medicinal uses for White Dead-nettles. These include treatment of menstrual problems such as heavy painful periods, kidney and bladder complaints, and use as a soothing lotion for the eyes or to treat piles and varicose veins. (The usual wise words apply: “Always seek advice from a professional before using a plant medicinally.“) The Eldrum Tree website also suggests some more mystical uses for the plant.

White Dead-nettles are normally so abundant that picking the leaves and flowers from the wild will have no ill effect. They make a pretty and long lasting cut flower (especially if you remove some leaves to reveal the flowers) and an attractive garden plant, though they may come to visit your garden without an invitation and decide to stay.

So far, I have just one plant in a large pot in the back garden as an attractant for bees, but I allow some large patches to grow at the edges of the allotment. Unwanted plants are easy to dig out with a hand fork or, when very established, a garden fork. The plant does well as ground cover in sunshine or light shade, and thrives in full sun on more fertile soils, including light ones like on my allotment.

If you want to grow Lamium album but can’t source it from a fellow gardener, it is possible to buy plug plants from a variety of places, including Naturescape and Landline Wildflowers.

In recent years several scientific papers have explored the biochemical properties of White Dead-nettles. These include “Revealing the reviving secret of the white dead nettle (Lamium album L.)” (note 4) and “A review on biological effects of Lamium album (white dead nettle) and its components” (note 5). Extracts from Lamium album have been shown to have antiviral, antimicrobial, antioxidant, anticancer, cytoprotective, wound healing and antidiabetic effects.

The BGFlora.eu website lists several of the phytochemicals in Lamium album.

The plant was also a favourite source of chlorophyll and other plant pigments for Mikhail Tsvet, (1872 – 1919), the inventor of chromatography.

If you don’t have your own laboratory, simpler pastimes are available.

Flora Britannica records that country children sucked the nectar from the base of the flowers, and that “boys used to pick the flowers off dead nettles and chase the girls pretending they were real stinging nettles” (note 5). Who needs a Playstation?

Notes

Note 1 – I have also written about other members of the Lamiaceae (Mint family), including Water Mint, Ground Ivy, Rosemary, Wild Clary, Balm-leaved Archangel and various Sages (Salvia), including Salvia ‘Hot Lips’. It is one of my favourite families of plants, with 236 genera and around 7000 species worldwide.

Note 2 – A picture paints a thousand words, so as usual I recommend a look at the superb Wild Flower Finder website for photos.

Note 3 – “Archangel” is an alternative name for dead-nettles, possibly given because the plants don’t sting. Another alternative suggestion is that the plants come into flower around the day dedicated to Archangel Michael (8th May in the Roman Catholic church).

Note 4 – Yordanova, Z.P., Zhiponova, M.K., Iakimova, E.T. et al. “Revealing the reviving secret of the white dead nettle (Lamium album L.)”. Phytochem Rev 13, 375–389 (2014). https://doi.org/10.1007/s11101-014-9356-2. (Only an abstract is available to the general public.)

Note 5 – Pourmirzaee, T., Abedinzade, M. and Ghorbani, A. “A review on biological effects of Lamium album (white dead nettle) and its components.” Journal of Herbmed Pharmacology 8(3), 185-193 (2019). https://www.researchgate.net/publication/334486062_A_review_on_biological_effects_of_Lamium_album_white_dead_nettle_and_its_components. (A PDF is available to download. I wish all scientific papers were as easy to access.)

Note 5 – Richard Mabey (1996): “Flora Britannica“, Sinclair-Stevenson, London. page 314.