Oenothera - Evening Primrose - Biennis
This biennial has large scented flowers, and is great for attracting butterflies and moths.
For best results, sow seeds onto a good soil-based compost. Cover the seeds with fine grit or compost to approximately their own depth. Although they can be sown at any time, these seeds may sometimes wait for spring before emerging, but spring sowing will obviously give them a full season of growth.