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Tansy plants

Along the river Ouse the Tansy beetle’s food plant is Tansy (Tanacetum vulgare).

The tansy plant can grow up to 100cm in height and has toothed, pinnate leaves. When the leaves are crushed they release a strong odour.

The tansy plant is a member of the Compositae family whose main feature is the composite flower type. In tansy there is a cluster of yellow buttons (capitula) at the top of the plant. Each button is comprised of a tightly packed disc of florets with no exterior ray florets. Tansy is often mistaken for ragwort, which does have ray florets. 

Tansy and Ragwort comparison

Tansy and Ragwort comparison

Tansy beetles will eat plants other than tansy. Available evidence suggests the beetles that were once found at Wicken Fen in Cambridgeshire and fed on water mint (Mentha spp.). Other reports claim gipsy wort (Lycopus europaeus) and marsh woundwort (Stachys palustris) have also been eaten by the beetle.

Other potential food plants

Other potential food plants

The Tansy plant has been used throughout history. For centuries tansy tea has been prescribed by herbalists to expel worms because it is highly toxic to internal parasites.  Furthermore, its toxicity to insects delays spoilage of meat, whilst planting tansy alongside potato repelled the Colorado potato beetle.

At one time omelettes were flavoured with tansy and tansy cakes were eaten at Easter. In Yorkshire, tansy and caraway seeds were traditionally used in biscuits served at funerals.

Please note: eating tansy is not recommended.