Broomrape

Belgian white carrot in a broomrape embrace

Belgian white carrot in a broomrape embrace

We have a moderate infestation of broomrape (Orobanche minor) on our property. It shows up here and there in perennial beds and in the vegetable garden.

Broomrape is a parasitic plant. It contains no chlorophyll, and when it is not flowering, the entire plant is below ground. Its fibrous, root-like tentacles encircle the host plant’s roots, sucking off nutrients and water from the host.

Though it “officially” prefers clover, in the vegetable garden, it seems particularly fond of carrots. I regularly find carrots being strangled in a broomrape embrace.

The gardener in me is dismayed every time I find one.

The scientist in me is fascinated.

Many parasites are very host-specific, that is, they only live on one or a limited number of host species. Orobanche minor appears to have a wide host range, but there is evidence that individuals parasitising different species are actually genetically isolated from one another, because the parasite’s reproductive cycle is tied to the host plant.

Eventually, that isolation could cause Orobanche minor to speciate…or maybe it has, and we haven’t noticed yet.

Perhaps some day my carrot-loving parasites will be different enough from my clover-loving parasites that they will have a new name. Maybe Orobanche carota!

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