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The importance of ‘teazle’

River Calder at Copley by Kelly Mundy
River Calder at Copley by Kelly Mundy

If you wander the riverbanks of the valley at this time of year, you won’t go far before stumbling across Dipsacus fullonum - known as teazle, writes horticulturalist and gardener Simon Zonenblick (pictured) in the first of a number of occasional articles for Go.

Teazle (also written “teasel,” and “teazel”) is a herbaceous biennial in the family Caprifoliaceae, and produces its trademark, thistle-like flowerheads in its second, final year.

The purplish flowers are arranged upwards along a bulbous flowerhead.

The florets composing this inflorescence contain four stamens (male organs) and a single white pistil (female organ).

Each flowerhead contains up to two thousand florets, in varying stages of development.

In bud, the flowers are protected by spine-like bracts, tapering like tiny knives and lengthening as they near the flowerhead’s apex.

Further green bracts arrow from the base of the flowerhead and curve upwards, bristled by spines, while the Latin prefix Dipsacus is drawn from the stem leaves’ habit of forming cup-shaped structures trapping water (Dipsacus meaning thirst for water).

This has led to the adoption of Venus’ Cup as one of many common names.

Replacing the former earlier sylvestris (from forest or wood), the suffix fullonum has more prosaic origins - the flowerheads were used to tease out wool by fullers in spinning mills, hence another aforementioned common name, “Fuller’s teazle.”

Teazle, which grows naturally across much of Europe, much of Asia and North Africa, as well as being introduced in the Americas, Australia, New Zealand and South Africa, is a very important plant in terms of biodiversity, feeding ladybirds, bees, wasps, and birds.

Insect-hungry tits are drawn in by the profuse available prey, while goldfinches have become associated with the plant, as we shall see.

But the plants also have a grislier side, first documented by Frances Darwin.

While the water-collecting leaves prevent sap-sucking aphids ascending the stems, researchers have demonstrated, by adding and removing dead insects from leaf bases, that seeds increase with the addition of insects, suggesting partial carnivory.

When the flowers die, their purple prongs are replaced by brittly brown cones, standing like rows of spiky soldiers through late summer and autumn, into winter.

But there is a barbed beauty about the expired flowerheads, and it is when the plants are denuded of summer finery that they perform the function for which they have, ecologically, become most prized.

Goldfinches’ razor-thin beaks are perfect for tweezering tiny (four to six millimetre) seeds from between spikes.

And it is for this reason that the plants are specially grown on nature reserves and in gardens, boosting the numbers of these delightful birds, recovering from decline in the 70s and 80s.

Teazle is distinctive in its purple spikiness, forming swathes of soft colour blending against green and watery environments, and attracting a host of beneficial insects and birds to gardens, nature reserves and open spaces.

Even in its flowerless winter form, this beguiling, beautiful plant plays a significant role in the eco-system, and is an important piece of the jigsaw of ecology.