| Common Name | Cosmos, garden cosmos, Mexican asters |
| Genus | Cosmos |
| Species | C. bipinnatus |
| Family | Asteraceae |
| Life Cycle | Tender Annual |
| Tray Size | 8 |
| Plug Care | Harden off and plant or bump up soon after receiving. Cosmos are very quick growing and will soon become rootbound if left in the original plug tray. |
| Netting / Staking | One or two layers of netting is beneficial in areas with high wind. |
| Temperature Range | Plants can not tolerate freezing at any point in the growth cycle. They can handle the heat of summertime and are a crop suitable for most zones. |
| Spacing | 9-12" |
| Soil Preference | Loose, well draining soil with low fertility. Too much nutrient content will cause heavy foliar growth and few flowers. |
| Day Length | Short day plants - flowering is triggered as days get shorter, typically towards the end of summer. If stressed rootbound or drought conditions) they will flower prematurely. If growing in a greenhouse through the winter, additional lighting will be required to mimic long days for the vegetative state. |
| Pinching | Pinch once when the plants are about 6" high, down to a few sets of leaves to encourage side branching. If the plants try to flower prematurely, continue to pinch off buds and flowers until you start seeing longer stems. |
| When to Plant | Plant in the spring after all danger of frost has passed. Succession sow 2 or 3 times (about 4 weeks apart) for continuous blooms through to frost. |
| Harvesting | Expect flowers approximately 45-60 days after planting plugs (dependent on weather and temperature). Harvest when flowers are just starting to open for the longest vase life. Mature side buds will also open in the vase. Cut deeply into the plant for long stems and to promote additional side branching. If flowers are left to open fully they will get pollinated and vase life will suffer. |
| Post Harvest Care | Place cut stems immediately into cool water. Floral preservative will extend vase life - expect stems to last just shy of one week. Can be stored in the cooler for a short period of time. |
| Diseases / Insects | During long stretches of heat and humidity powdery mildew and bacterial wilt may be seen. Common insect pests include aphids, thrips and Japanese beetles. |
| Bailey's Notes |
Do not allow plants to set seed - keep up with harvesting and deadheading or the plant will start to shut down. Some growers will use stems of cosmos foliage as a filler in bouquets - they have reported a good vase life although we don't have personal experience to support this claim. |
| Resources | NA |