Something’s Got a Hold of my Root: Broomrape (Orobanche)

This is a sort of opener for a series on telling similar plants apart, but I also wanted to say something about these remarkable flowers.

Orobanche gracilis - slender broomrape. Its host,the legume Dorycnium, is in the background

Orobanche gracilis – slender broomrape. Its host,the legume Dorycnium, is in the background

This was the first of these striking inflorescences I saw – pointed out to me by CL, who must be developing a botanist’s eye in order to be able to live with me. It’s Orobanche gracilis, slender broomrape, and like all plants in this genus it’s a parasite, living entirely on the water and nutrients of its host plant , which for this species can be any legume (Fabaceae family – anything resembling peas and beans).  The plants are distant relatives of snapdragons and toadflaxes, which you can see in the shape of the flower and the form of the inflorescence.

O. gracilis close up, showing the red markings

O. gracilis close up, showing the red markings

With  its distinctive red markings inside the flower, it’s beautiful in a rather weird way , partly due to the absence of green – the plant has no  chlorophyll at all – and partly because I can’t bring myself to like a plant that preys completely on something else. Its human equivalent must be the thief, the pimp, the drug dealer – I’ll come back to that.

A dry stem of broomrape - O. picridis or O. minor?

A dry stem of broomrape – O. picridis or O. minor?

Within a week or two, I’d found another broomrape, this time in the sand dunes, but all that remained was a dried flower stalk. I’ve since found another, very similar but equally dry, in the next village to mine. So, some detective work needed. I’ve narrowed  the main possibilities for these to two:  Orobanche minor, or O. picridis, since both were tall and slim, with small flowers, and near what looked like a Picris – a species of oxtongue with a small dandelion-like flower. They could be one of each – and O. minor is said to be found near the sea and also parasitises composites like Picris, as well as legumes.

This leads me to the difficulty of identifying broomrapes in general – they’re mostly in shades of yellow through to pink, most have a single spike of whitish flowers, and to make matters worse, most are variable in appearance depending on soil, location and host. But there is one main clue to note: they are usually pretty close to their host plant. This helped me identify the next broomrape I found, on the sauveplaine. There were a couple of small colonies, both next to, even growing through the leaves of their host plant, Eryngium campestre or field eryngo.

Orobanche amethystea just emerging

Orobanche amethystea just emerging

This is Orobanche amethystea, which parasitises a variety of plants, mostly umbellifers like Eryngium (members of the family now named Apiaceae).

O. amethystea growing through leaves of Eryngium

O. amethystea growing through leaves of Eryngium

Orobanche amethystea close up

Orobanche amethystea close up

What about the strange names for these blooms, with their echoes of violence? Broomrape comes from the Latin name for one species parasitic on broom – O. rapum-genistae – rapum (the Latin word for turnip) in this case signifying the root-swelling where the parasite has taken hold. Orobanche comes from orobus (vetch) and ancho (strangle).

I wondered how the life-cycle of Orobanche could work, given that it has to  find a host,  and that cross-pollination must be as rare as the plants. They often self-pollinate, and the flowering heads can each then produce  100,000 tiny seeds. These are the seeds from one of the dried plants – each seed is only a tenth of a millimetre across.

Orobanche and seeds

Orobanche and seeds

The seeds can lie dormant in the soil for years, until stimulated by chemicals from the roots of a living host plant (for more on the  social life of plants, see my post here).  The seed then germinates, sending a small rootlet towards its host root and boring in to the vascular tissue.  This creates a bulge or tuber on the root, from which the flower will eventually arise – after which the broomrape dies. While they are rare in Britain, and often protected, they are a significant problem for agriculture in other areas, principally dry regions such as North Africa and the Near East. Orobanche crenata parasitises broad beans, and it’s estimated that Egyptian farmers lose up to 40% of their crops to this predation. The tiny seeds are easily spread by animals and farm machinery, and the problems there, and in Morocco and Algeria, are increasing.  Farmers will have to pick the flowers before they set seed, and clean tractor tyres to contain the spread.

How to find the jazz in all that? Well, I’ve just been reading  So What, the superb biography of Miles Davis by John Szwed (who wrote the equally brilliant bio of Sun Ra, Space is the Place). Davis comes over as little more than a parasite in his relationships with non-musicians, especially with women.  And a thief and a pimp at times. He was so insecure, so dependent, so demanding, and without them he was cocaine-addled and dormant.  But there’s the life, and there’s the work, and my admiration for and love of the man’s music is undimmed by his portrayal.  Here’s something from just one of the revolutions Miles wrought in music, often, as here, with the help of his friend Gil Evans: the Birth of the Cool, and Moon Dreams.

Coming up next: They’re as alike as two peas – hang on, they are two peas

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3 Comments

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3 responses to “Something’s Got a Hold of my Root: Broomrape (Orobanche)

  1. I recognised the broomrape in your photo but ours look a bit different here. I headed off to find out if ours were invasive species but from what I can see they are natives…”The native broomrape (O. cernua var. australiana) and another introduced broomrape (O. minor) are present in Tasmania but not considered to be a weed problem and do not come under the broomrape declaration.” We have enough parasitic and hemiparasitic species in Australia without introducing more ;). Love the jazz, a great way to mellow out after walking the dog on a cold winters day in Tasmania :).

    • Glad they’re not a weed problem in Tasmania at least – they’re not here, either. Increasingly, as I’m researching and writing this blog it seems to me that gathering great swathes of one species of plant together in fields – or vineyards – is unnatural, and only invites pests to come in and multiply too. It’s not the fault of the broomrape, or poppies, or any other ‘weed’. If we avoid ‘weed invasion’,I guess it’s only a sign of how many chemicals are used. But I suppose the alternative is hunter-gathering, which I’m not prepared to do. One of those questions of balance….

      • How I wish we had poppy problems! Ours run to gorse, blackberries and spear thistles…it would seem the international weeds that do the best here are heavily armed :(. Oh for broomrape! I had to be VERY careful how I worded my querie when I was hunting for “Broomrape in Tasmania” 😉 The natives are well known for being somewhat distinct (I am not a native Tasmanian, I come from Western Australia 😉 )

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