Monday, June 13, 2011

Vegetable Vampires 1: Common Cow-wheat

Backstone Bank wood near Wolsingham in Weardale has an interesting ground flora - one factor that qualifies it for SSSI status - and it includes this attractive little plant that blooms amongst the bilberry around the western edge of the wood. This is common cow-wheat Melampyrum pratense and although it looks harmless enough it's a partial parasite (hemiparasite) on the roots of bilberry. Its green leaves carry out photosynthesis and produce sugars but its roots invade those of the bilberry, siphoning off water and mineral nutrients.
Specialist hemiparasites like this thrive in soils with low fertility where there is intense competition for essential but scarce minerals, like nitrogen and phosphorus, because they are the botanical equivalent of vampires, tapping into the internal plumbing system of their host to supplement their own nutrition.


This is common cow-wheat but for pictures of its much rarer cousin small cow-wheat Melampyrum sylvaticum take a look at Mark's Beating the Bounds blog.

Some plants (holoparasites) have taken parasitism one step further, losing their chlorophyll and becoming totally dependent on their host for all their nutritional requirements - you can find a common example here and an extremely rare and beautiful example here.

10 comments:

  1. That humans are parasites can't be denied: as a species they draw out all their nutrients from the planet and generally give nothing in return. The question is: did parasitic plants learn their way of life from humans, or did humans learn from plants?

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  2. Fascinating stuff. I knew Common Cow-wheat was considered a parasite, but never knew just how it benefited from other plants. Thanks for the explanation.

    I've seen it growing among the Blaeberry at Glenmore, in the Cairngorms.

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  3. PS I should have said "Modern humans" :)

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  4. Fascinating! The flower is so pretty. The sandalwood tree which is quite common here, is said to be a semi parasite too.

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  5. Hi fernenland, parasites have been around since the life first evolved....

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  6. It seems like a good year for it here swanscot - there were hundreds of plants flowering in this population...

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  7. I didn't know that about sandalwood lotusleaf - thanks!

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  8. Another species unknown to me even though I lived the start of my life in Bilberry country.

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  9. Hi Phil,
    Nice to see this cow-wheat and to learn that it needs a specific host plant. In your photo, the common cow-wheat doesn't look so different from the plant I photographed - I had thought from readiong 'The Wild Flower Key' that there were more obvious distinctive differences - now I'm wondering if I've misidentified what I saw - I'm pretty sure that there was bilberry around where I saw it.

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  10. You said:
    "It seems like a good year for it here swanscot - there were hundreds of plants flowering in this population... "

    Here too. We're a little bit later up here, but now, this week, I saw loads of this in the woods on the edge of the camp site.

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