70-77 days. Annual. Purple Knight Alternanthera seeds promise an exotic and neat ornamental foliage ideal for many humid gardens across North America. Purple Knight seeds mature into robust 18-24 inch tall mounded shrubs of rich purples and reds spreading out for an eye-catching trim along walkways, borders, and fences. Alternanthera is native to the perennial warmth of Asia, Africa, and Australia and will thrive all season in similar climates. Purple Knight alternanthera is easy to grow from seed and guarantees a unique and low-maintenance ground cover for any residential or commercial property.