Mistletoes and galls

[no, not Gauls… those are the Asterix’s friends, who use mistletoe in their magic, strength-giving, potion.  This is about GALLS – an entirely different thing, but still with mistletoe connections…]

Cecidology, or the study of plant galls, abnormal plant growths caused by specific animals or other plants, might seem to be a rather specialist subject.  But it has a significant, and growing, folllowing amongst both professional biologists and amateur naturalists.  It even has its own society, in the UK – the British Plant Gall Society (BPGS).

The picture shows a Robin’s Pin Cushion Gall, a particularly weird abnormality of wild roses caused by the larvae of specialist gall wasps.  Other, better-known, galls include oak-apples, and acorn ‘knopper’ galls, caused by specialist gall-wasps.

I was, I guess, a founder member of the BPGS back in the 1980s, set up after the late Fred Stubbs, a Yorkshire-based cecidologist put an ad in the national wilife press asking for contact with other gall enthusiasts.  My own natural history interests have always been biased towards the wildlife underdogs (none of that populist bird-watching lark for me!) and so I was an easy recruit.  Indeed I had already got a significant grounding in galls, having acquired Arnold Darlington’ pioneering (1968) Pocket Encyclopedia of Book of Plant Galls as a teenager, and I had followed this up with a study of economic uses of tannin-rich galls (particularly in making the permanent ink used by the Bank of England for bank notes – gálls were a key ingredient in ink manufacture) as a post-graduate studying industrial archaeology in 1983/4.

The big problem for gall-enthusiasts was, in the 1980s, the lack of any readily available literature – how could you find out more about galls, and what caused them?  The BPGS were the immediate solution, producing Keys and a range of other specialist guides (see them all here).  But we were still missing a definitive overview text.

So, I was very pleased, last week, to get a parcel from Margaret Redfern, a stalwart of the BPGS, containing her long-awaited book Plant Galls the latest in Collins’ highly-esteemed New Naturalists series.  I’ve not had a chance to go through all 560 pages in detail yet – but a quick skim suggests it is all, and more, that a gall-lover needs, and so I already recommend it!

But why am I including this in a mistletoe diary posting?  Well, you might not have realised it but mistletoes are gall-causers – the distortion and swelling of the host tree at the point of infection by a mistletoe is technically a gall.

So, next time you look at a mistletoe do consider its status as a gall causer, and look more closely at the host/parasite structure. (I’ll look out some good mistletoe gall pics and post them later…)

And, if you want to know more about galls in general, do buy Margaret’s book (it tells you about the industrial uses of galls too!)

And join the Gall Society – it’s only £10.00

2 thoughts on “Mistletoes and galls

  1. in arizona mistletoe has been know to cause large galls on mesquite trees. we found one approx. one foot in length and 1/2 foot in width. have you ever seen such a thing? I am a writer form IMAGES. AZ and am trying to get info

    1. Hi Jano, Thanks for your comment. Yes mistletoe haustoria can sometimes be very large – and so can form gall structures of a foot or so. Bear in mind that many mistletoe species are very long-lived, and as long as the host tree branch can still cope with the infestation the resulting formation can become very complex – a haustorial structure that is, say, 25 years old or more will inevitably be quite large.

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