With showy colors and a classic wildflower look, Cosmos are an easy to grow and beautiful addition to any garden. Learn how to plant and grow Cosmos right here with our detailed guide!
Table of Contents
Basic Facts
| Common Names | Cosmos, Garden Cosmos, Mexican Aster |
|---|---|
| Botanical Name | Cosmos sulphurus (shorter variety); Cosmos bipinatus (taller variety) |
| Family | Asteraceae |
| Zones | Grown as an Annual. Easy to start from seed each year. Self-seeds prolifically. |
| Flower Colors | Reds, Pinks, Orange, Yellow, White. Varieties are normally pastel. |
| Height & Spread | Most varieties grow anywhere from 1-4′. Some of the taller varieties might need to be staked if you plant them in a windy area. |
How to Grow and Care For Cosmos
When to Plant Cosmos?
This is one of the easiest plants to grow from seeds sown directly in the landscape. Wait until all danger of frost has passed and the soil temperature reaches at least 65 degrees. The seeds will germinate after a week or two.
If you’re buying your Cosmos instead of growing from seed, mid-summer is the best time for planting. Cosmos prefer warm weather and will start blooming more once the days start getting shorter. Thus, mid to late summer and early fall will be prime time for your Cosmos plants.
What Type of Soil Do Cosmos Like?
Unlike many other common annuals, Cosmos actually prefer poorer, infertile soils. This means that no special preparation is usually needed when planting Cosmos. If planted in soil that is too rich, the plant might grow leggy and weak. Be sure the soil or potting mix is well-draining.
Do Cosmos Need Sun or Shade?
Cosmos will do well in either full to partial sun, although full sun would be preferable.
How Often to Water Cosmos
Cosmos are drought-tolerant and established plants don’t require much, if any watering. However, Cosmos that are still watered every now and then should produce more blooms.
When to Fertilize Cosmos
You do not need to fertilize Cosmos. In fact, they will actually perform better if you don’t ever fertilize them!
Potential Pests & Diseases
- Cosmos are normally resistant to most common plant pests and diseases.
