Every garden should have this long flowering beauty which flaunts its sprays of fragrant purple flowers, on wiry angular branching stems, from June until the frost. Acts as a magnet for butterflies. SOWING ADVICE: For best results, sow immediately onto a good soil-based compost. Cover the seeds with fine grit or compost to approximately their own depth. They can be sown at any time, and germination can sometimes be quicker if kept at 15 to 20 degrees C. We sow most seeds in an unheated greenhouse and wait for natural germination, as many seeds have built-in dormancy mechanisms, often waiting for natural spring germination, hence giving them a full season of growth.