Dark Mullein Seeds verbascum nigrum – grows best in dry grassland and is well suited to sandy or chalk and limestone soils, on sites where there is plenty of sunlight. Plants attract a wide range of insect life such as Bees. Dark Mullein is a tall growing species that produces spikes of soft yellow flowers. These will remain in bloom from June to September. It is a perfect wildflower for growing in a garden border and will produce a tall stately plant if raised in a fertile soil. Dark Mullein looks best growing with other chalk and limestone plants that flower in early to mid summer such as Oxeye daisies, Greater Knapweed, Meadow Cranesbills and Small Scabious.