Teasels

Fuller's Teasel, Dipsacus fullonum, a common sight in open weedy places. As non-native invaders go, this is a pretty spectacular plant and a species familiar to and identifiable by even the most casual of botanists.

Teasels, most of which are indigenous to Europe, were once used in the manufacture of textiles. The incredibly stiff, sharp bracts of the flower heads were used to tease cloth or raise the nap on wool products, and to ensure a ready supply, teasels were planted around cloth plants.

They jumped the garden fence long ago, and have been a part of our landscape for most of the past century. And for most of their life on the lam here in the States and Ohio, it was the lavender-flowered Fuller's Teasel that was the common species.

The short-cylindric flower spikes are actually rather showy, but I never seem to see much in the way of insects nectaring at them. There are over a dozen species of teasels, but only three have shown up here. And one of those, the Indian Teasel, Dipsacus sativus, was only collected from two southern Ohio counties long ago. I've never seen that one.

The generic name Dipsacus roughly means "thirst", and probably refers to the cuplike bases of some species. Fuller's Teasel leaves do not form much of a cup, but do show the opposite leaves and overall coarse look that is typical of teasels.

There's a new sheriff in town, and it's this prickly behemoth, the Cut-leaved Teasel, Dispsacus laciniatus. I remember gasping in wonder when I first saw this thing, growing along the verge of U.S. 23 in Pike County in the early 1990's. Jamming on the brakes, I jumped out and made a voucher specimen.

In the 15+ years since, this white-flowered teasel has marched along our highway system - a common avenue of plant dispersal for non-natives - and has colonized a big chunk of the state. Fernald, in the 8th Edition of Gray's Manual of Botany (1950), states that it is "local" in eastern North America. Tom Cooperrider, in his 1995 Dicotyledoneae of Ohio, records it from 19 rather scattered Ohio counties. Today, I dare say there are specimens of Cut-leaved Teasel to be found in all 88 counties, and in many locales it is locally abundant.

Cut-leaved Teasel is even more robust than Fuller's Teasel and a well-formed specimen can tower over a man's head. It is also beset with more prickles and I should not want to be sentenced to 20 lashes by teasel stems. I also find these massive biennials to be far more invasive than the Fuller's Teasel. Their basal rosettes of leaves can form a carpet so dense that they exclude nearly everything else, and when the flowering stems shoot forth, watch out - it is a giant prickly teasel forest.

All of its nastiness aside, there is a fascinating aspect to Cut-leaved Teasel morphology that hasn't been well-studied insofar as I am aware. The robust leaves, which are connate or joined at the base, form tremendous foliar cups that hold water for extended periods. It has been speculated that these water traps form a barrier to aphids that attempt to climb the plant, and thus prevent them from effectively tapping into the plant's tissues.

Hmmm... Could be.

But, when this sort of water-retaining structure is present on a plant, one has to wonder about the possible evolution of carnivory. There is no question that insects become trapped in teasel leaf-pools and perish. Does the plant then successfully break down and assimilate the insect's proteins and other valuables? It's probably worth a study.