Stingless nettles

Normally, the leaves of stinging nettles are covered in stinging hairs (trichomes) that when broken (e.g. by contact human skin) release chemicals that cause stinging/ itching. This works because the trichomes are covered in a very thin layer of silica (effectively glass) which snaps upon contact to release the irritant chemicals inside. In the lab, nettles grown without silicon lose the ability to sting