Cosmos, Rubenza – Cosmos bipinnatus

Life cycle: Annual / Ease of propagation: Easy / Hardiness zone: 8-11

Cosmos is a low maintenance, drought-tolerant flowering annual. Cosmos “Rubenza” has gorgeous, ruby colored 3-4″ blooms that is perfect for cutting. This species (Cosmos bipinnatus) has white, pink, and red flowers and is more commonly grown for floral arrangements. It will not cross with orange cosmos (Cosmos sulphureus), which is good to know if you want to grow both plants in the same space.

Though cosmos are native to a temperate climate (Mexico), our experience shows they are hardy. Our cosmos re-seeded in September and the new seedlings began blooming from late October to November, even after a couple light frosts. If you’re looking for a strong, vigorous flowering plant to add beauty and attract pollinators to your garden, cosmos is it. Cosmos can reach up to 7 feet tall and will bloom continuously from early summer through late fall.

Cosmos can tolerate drought so choose a dry, sunny location with sandy, loamy, well-drained soil. Areas with hot summers are perfect for growing cosmos.

Sowing Instructions

Sow indoors 5-7 weeks before planting outside or direct sow after danger of frost has past. Cover seeds with four times their thickness in soil. Maintain a temperature of 68-75° F during germination (a heat mat may be needed in regions with cold springs). Once plants reach at least two sets of true leaves, plant out seedlings 9-24″ apart.