Othello
In his speech about gardening, Iago talks of planting nettles. Those are the stinging nettle, a common plant that grows everywhere. It is a plant of much virtue. It can amend many diseases and is very good for purifying the blood. But its stalk has many frail sharp spines, each with a little pouch of burning venom at its base, awaiting any unwary hand that merely brushes it.