Lavender (Lavandula angustifolia, also known as true lavender) is an evergreen, strongly fragrant sub-shrub in the mint family, originally native to the dry, sunny coastal regions around the Mediterranean — from Dalmatia and Greece to Tuscany. Its narrow, grey-green leaves are softly felted, and from June to August it blooms in characteristic spike-shaped flower heads in shades of violet, blue, or pink. Lavender grows to about 30–60 centimeters tall and attracts bees and butterflies. Benedictine monks introduced the plant north of the Alps; being winter-hardy, it has since naturalized in places such as Jena, Rudolstadt, and Bad Blankenburg in Germany. To this day, the vast, violet-blazing lavender fields of Provence, especially on the Valensole plateau, shape the plant's image in the Western imagination.

The name lavender likely derives from the Latin lavare, "to wash" — the Romans scented their bathwater with it, and prized it so highly that a pound of its blossoms could cost as much as a farm labourer's monthly wage. It later became a staple of monastery gardens across medieval Europe, grown as much for medicine as for fragrance. It was carried in small sachets to ward off plague-bearing insects, strewn on floors to freshen homes, and used by herbalists for centuries as a remedy for headaches, nerves, and sleeplessness. Gerhard Madaus wrote in his 1938 "Textbook of Biological Remedies" that lavender is "a mild nervine, particularly favoured for migraine," prescribed for neurasthenia, nervous palpitations, and insomnia. The herbalist Matthiolus praised it in verse as a "precious herb against all cold afflictions of the brain." In folk traditions across Europe, lavender was also considered a plant of protection, tucked into linens and cradles to guard against bad dreams.

Dried lavender flowers release a sweet, floral, calming scent with balsamic undertones when burned. Its smoke is lighter and airier than resinous incenses, traditionally used for stress, restlessness, and headaches, and still burned today to soothe the mind and support restful sleep. It ranks among the mildest and most approachable of all incense plants. In medieval folk belief, lavender was also counted among the herbs of the legendary "four thieves vinegar," said to protect those who carried it from contagion.