Plant on Plant Parasitic Action.

This is probably the last (or nearly the last) post about my time in Florence. I think I’ve just about squeezed it till the pips squeak!

But I thought I couldn’t let it go without writing about yet another interesting plant that I found in huge quantities growing by the Arno (which seems to be a veritable hotbed of vegetable parasitism.)


This is the European dodder or cuscuta europaea; a rather attractive plant that wreathes it way through others with delicately spiralling tendrils. It looks quite inoffensive at first sight. What possible harm could it do?


Well it’s dodder by name but not by nature. There is nothing weak or failing about this particular marvel of nature. Those dainty tendrils twirl around the stem of their host plants and probe into their vascular systems, stealing their water and nutrients. The dodder is a very clever and successful plant. After germination it has very limited resources and unlike other plants it cannot photosynthesize, so it must very quickly find and attach itself to a suitable host. It’s not surprising therefore that the dodder has an amazingly efficient host – location mechanism.


Dodder uses airborne volatile organic compound cues to find their host plants; it could be said that they literally sniff out their favourite food. In  an experiment, dodder seedlings were observed to exhibit ‘positive growth responses to volatiles released by tomatoes and other favoured species – the tiny plantings send out tendrils in that direction. Apparently  they particularly fancy a nice tomato although they’ll put up with others plants if they have too. In the picture above they are infesting a wild geranium plant.



There were great swathes of dodder all along the Arno. Many plants wore it like a toxic feather boa. I’ve seen it growing in the UK, but it was always much smaller and insignificant.

In Italy it seems the Day of the Triffid is not just a nightmare fantasy.

About pennimania

Artist, entomologist, grumbler.
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