Red valerian (Centranthus ruber) growing behind a wall. This European herb, also called French honeysuckle, is a garden flower that is often seen by roadsides and in urban wasteland. It can tolerate very alkaline conditions and will grow in old walls despite the lime in the mortar. Red valerian flowers between May and September. It is pollinated by bees and butterflies and it produces a strong, unpleasent scent, similar to perspiration.