How to Grow Cosmos Flower Plants in Containers

Cosmos (Cosmos sulphureus), an annual plant native to North America, Central America and South America, produces showy blossoms that attract butterflies. Considered easy to grow, cosmos comes in numerous varieties, with daisy-like white, yellow, orange or red blossoms. It grows well in most soil types and is often grown in containers. Choose dwarf to compact cosmos varieties — which form dense plants with semi-double or double blossoms — to grow in containers, and always start with new seeds.

Container
Wire mesh
Potting soil

Instructions

- 1
  Obtain trays and containers with drainage holes. Use small containers for one or two cosmos plants, or larger containers to grow several plants together. Allow about 6 inches — half of the expected width of a mature plant — for each plant.
- 2
  Cover the drainage holes with a piece of wire mesh. Fill each container within 1 to 2 inches of the rim with potting soil. Don’t use a potting mix that contains fertilizer, which could interfere with growth.
- 3
  Sow one to two cosmos seeds in the center of smaller pots or every 6 inches in larger pots. Cover the seeds with soil.
- 4
  Water as needed to dampen the soil and then place the container in a location with full sunlight and a temperature range of 70 to 75 degrees Fahrenheit to encourage germination.
- 5
  Maintain moist but not soggy soil until seedlings emerge in one to two weeks. Thin the cosmos if needed when they reach 3 inches tall.
- 6
  Check the soil often and water it when the top inch of soil is dry. Add water until it drains into the tray, then pour that water out of the tray.
- 7
  Trim spent flowers to extend the bloom period. Pinch the cosmos stems or use pruners to control the size and to encourage bushier plants.

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