Monday, August 8, 2011

A bit doddery

On Sunday I walked around the RSPB reserve at Fen Drayton. It's only 15 miles or so north of here and is a complex of lakes next to the River Great Ouse in Cambridgeshire; a wonderful place where one can relish the open fenland landscapes and cloudscapes.
'Twas darned windy but the sun was deliciously warm in the morning and I took the opportunity, on a few occasions, to lie down in the long grass to soak up the rays. And it was also congenial to catch-up with the RSPB's Neil Renwick, who used to work at The Lodge, Sandy, and is still very much missed.

By the banks of the River Great Ouse I noticed some white-flowered creeping thistle (Cirsium arvense) and paused to take a photo.

I then noticed something scrambling around the thistles....
....and was thrilled to find it was greater dodder (Cuscuta europaea), a brilliantly weird plant that I'd not seen before. The UK distribution map here, indicates that it is not only nationally scarce but likes growing along river banks.

There are 4 species of dodder in the UK; greater dodder (Cuscuta europaea), dodder (C. epithymum), flax dodder (C. epilinum) and yellow dodder (C. campestris).

Gerard's (1597) general description of dodder still holds good...

All dodders (Cuscuta species) are obligate parasites; they live by stealing nutrients from their host plant. They don't have roots and don't photosynthesize (or at least not very much, greater dodder not at all). Yes, they're a bit of a pest on crop plants, but very interesting all the same. 
Different species of dodder specialise in parasitizing different hosts. Greater dodder's primary host is nettles (Urtica spp) but it will parasitize other plants nearby, in this case creeping thistles.
Dodder clambers up its host with its sinuous tendrils, binding itself around the host's stems. It attaches to its host via haustoria; specialised appendages on the stem which penetrate the host tissues. You can just about make out the swellings on the red dodder tendrils in the picture below; pillaging nutrients and water from this nettle.
Now, if you are a parasite or a predator you've got to be able to find your prey. Tiny dodder seedlings must detect and latch onto a host as soon as possible. Recent research indicates that dodder can 'smell' or 'sniff' its host species. Dodder apparently does this by sensing the unique chemical signature of its host plant. Research on Cuscuta pentagona which uses tomato plants as a host, indicates that dodder seedlings in a lab preferentially grow towards their hosts (in this case a tomato plant) or a cocktail of 'tomato chemicals', rather than just damp soil (Runyon et al., 2006).

Once it finds a host, dodder grows quickly, tangling its tortuous tendrils around its host in a vivid (in the case of greater dodder) red woven cloak, which smothers, but does not kill the host. On crop plants, this is economically costly, and in the US dodder is high on the most hated weeds list; in fact there are 53 species of dodder listed as noxious weeds in the US (USDA 2010).

Mind you, dodder was never very popular. John Pechey (1694) lacerates it in his Compleat Herbal;
So no mincing one's words there. Colloquially it has been called; devil's guts, devil's hair, hellbind, hellweed, witches shoelaces and strangleweed.

The stems of dodder species vary in colour from red to yellow-orange. The name dodder may be from the old Dutch word doden for egg yolk, or from Dutch/German words dodd meaning 'a bunch' or dot meaning 'a tangled thread' (Johnson, 1866).

The pale creamy pink flowers of greater dodder are borne in a ball on its red tendrils, sometimes strung between host plants, like washing lines.

At Dungeness in June, dodder (in this case the smaller Cuscuta epithymum), was tangled over Nottingham catchfly (Silene nutans).
 
That's the old Dungeness lighthouse in the background.

Cuscuta epithymum has small pink flowers. The name epithymum by the way indicates that this species of dodder also parasitizes thyme; epi (on) thymum (thyme) (Johnson, 1866).

It looked like spaghetti.
Dodder was used as a herbal remedy; it's properties (allegedly) depending on the host plant it grew on, as Gerard (1597) notes that, 'The nature of this herbe changeth and altereth, according to the nature and qualitie of the herbes whereupon it groweth, so that by searching of the nature of the plants you may easilie find out the temperament of the laces growing upon the same.'

Turner (1568), without being specific as to which dodder to use, recommends it for 'stoppinge of the lyver and milte [spleen]. It discharged the baynes [?] of flegmatyk and cholerike humors by the urine. It healeth the iaundes [jaundice] that commeth of the stoppinge of the lyver. It is good for childer that have the ague. But much....of it hurteth the stomake...'

Gerard (1597) makes special mention of the 'dodder growing upon nettles' being 'a most singular and effectual medicine to provoke urine, and to loose the obstructions of the body, and is prooved oftentimes in the west parts to have good successe against many maladies.'

Very cool plants indeed.

Further Information on...
RSPB Fen Drayton. 

Neil Renwick's RSPB blog is here
Neil also runs a wildlife blog for the Cambridgshire News.
Dodder
Gerard J (1597) Herball or Generall Historie of Plantes. Online here.
Johnson GW (1866) The Wildflowers of Great Britain. On Google books here.

Pechey J (1694) The Compleat Herbal of Physical Plants. (I can't find an online version)
Runyon JB, Mescher MC and De Moraes CM (2006) Volatile chemical cues guide host location and host selection by parasitic plants. Science, Volume 313, pages 1964–7 (here)

Turner W (1568) A New Herball. Booke One (p113-4) (I can't find an online version)
United States Department of Agriculture (2010) Federal Noxious Weed List



Phil Gates has grown dodder in his lab and has written a blog about dodder (here). Fabulous close-up photos.

11 comments:

  1. You did well to fpot that ftrange plant!

    Great piece of writing, reseach and photos.

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  2. Fasinating Mel - I've never seen this plant in the wild, although I have grown it http://digitalbotanicgarden.blogspot.com/2011/08/dodder-cuscuta-sp-convolvulaceae.html
    Have you thought of collecting seed and growing some in your garden?

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  3. Hi Phil. Hmmmm. Not thought of growing it, but a most intriguing and tempting idea. Just popping into your digital garden now.......

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  4. Fascinating.

    I would think "baynes" would be "banes", poisons or toxins. The OED gives it as an alternative spelling.

    According to El Dioscorides Renovado by Dr P. Font Quer (I would have to go to the library to check the original) Dioscorides deals with the thyme parasite in Book IV, Chapter 179. Drunk with honey it purges phlegm and black bile by the bottom (por abajo, literally "by below" but I can't think of a better translation at the minute). Put in a small vinegar bottle up to four drams with honey, salt and a small amount of vinegar, particularly for those suffering from the melancholic humour and flatulences.

    Modern use in Spain (mid-20th Century) he reports as laxative and stimulating bile secretion. Recommended for constipation complicated with meteorism, a build up of gases.

    Mrs Grieves deals with Dodder here:

    http://www.botanical.com/botanical/mgmh/d/dodder16.html

    In Traditional Chinese Medicine the seeds are used but I lost my Pharmacopoeia years ago so can't give details.

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  5. Hi Pat.
    Thanks. Yes, 'banes' makes sense.
    I didn't look through my modern herbals but had noted from a few minutes of online research that one Chinese herbal use of dodder was as a sexual tonic.
    I like the way Mrs Grieve describes the effect of a bitter infusion of dodder as a 'brisk purge' - a rather dramatic 'cure' for constipation I think. Clearly the Chinese use of the seeds must procure a different physiological effect as a 'brisk purge' is hardly going to increase one's libido.
    I'm certainly not aware of any modern use of dodder in Western herbal medicine.
    Mel

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  6. I saw it on gorse at Holt Country Park, Norfolk, in August 2005. (Creeping Lady's-tresses also grows there - apparently introduced with the planted pine trees.)

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  7. Yo, Martin. The dodder is just grand. I have creeping ladies down on my hit-list this week :-)

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  8. Pleased you liked the photo of dodder.

    You may be a bit late to find Creeping Ladies-tresses in flower this year. At Holt CP it seems to end in early August. Haven't been for a few years (got some non-digital photos somewhere), but I assume it's still there. Last time (2005?) it looked a bit under threat from brambles. I suppose i should have checked this year, but (like you) I was more interested in shells on the beach.

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  9. Oops. I didn't notice (brain clearly elsewhere) you said creeping LT (Goodyera repens). My hit list is for autumn LT (Spiranthes spiralis). I've seen CLT in Scotland in the Caledonian pinewoods. I had no idea that it grew in Holt CP!! Blimey, a quick visit up there is most tempting! Autumn LT is in flower now in Kent. Not sure when I'll get to see it down there, but I intend to flit over to Worcs to see it there.
    I'd be disappointed if Holt CP weren't managing the site to control the brambles...

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  10. We have had a walk along the coast from Westward Ho towards Clovelly today on the North Devon Coastal path. We saw masses of 'dodder' all amongst the gorse bushes as we walked along. It was very dense and is quite strange to see. Looks like thick spiders webs, only it's very clearly vegetation of some kind. Mike

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  11. Hi Mike. I am envious! It's been a while since I did that walk. Hope weather was OK. Dodder is fabulously weird and can almost swamp plants it grows over. I may get back to Fen Drayton this week so will go revisit the dodder. Thanks for your comment. Mel

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