I know it is a weed, but I would not be able to identify it so would like to buy from reputable supplier.
They are fully hardy to frost tender, min 5-15C, and will grow well in sun or partial shade with moist but well drained soil.
Sow the annual seeds in the spring, the hardy perennial as soon as the seeds are ripe, you can divide the perennials in the spring.
Pests, diseases or disorders
Watch out for grey mould, aphids and mealbugs.