Bulgaria produces between 40 and 50 per cent of the world's rose oil, and almost all of it comes from this valley. The plant is Rosa damascena — the Damask rose — introduced from the Ottoman empire in the 17th century. The combination of mild winters, cool spring mornings, and well-drained soil at 350–400 metres turned out to be very nearly ideal.
The harvest runs from the second week of May until mid-June, depending on the weather. Pickers start before sunrise and must finish before the day warms up — the volatile oils evaporate quickly once the temperature climbs. If you drive the valley roads at first light during the season you will pass workers in the fields, often whole families, picking by hand into wicker baskets. Several distilleries near Kazanlak run short visitor tours; ask at the Rose Museum for current options.