Stock DBL Mixed - Flower SeedsOverview Stock Double Mixed Flower Seeds are a popular variety of stocks, also known as Matthiola, that feature double blooms in a mix of different colours, including shades of pink, purple, red, and white. These plants grow up to 12 18 inches tall and produce fragrant, showy flowers that bloom in clusters from late spring to early summer. They prefer full sun and well drained soil and are relatively low maintenance. Stocks are often grown as annuals