How to Care for Orange Cosmos

Pull or hoe out weeds that germinate around the young or mature orange cosmos plants. Cosmos develop thin, wide-spreading but shallow roots. Nearby weeds rob the cosmos of soil moisture and nutrients, and if the weeds get too large, block sunshine from reaching the plant's leaves.

Supplement rainfall with water from the irrigation system or a sprinkling to maintain an evenly moist soil during the heat of the growing season. Overly dry conditions cause orange cosmos to wilt. While soggy soil must be avoided, allowing the soil to slightly dry out between watering is fine.

Pluck off old flower heads from orange cosmos, a process known as deadheading. Using a scissors, snip off the withering flower by making a cut down the flower stem where it attaches to the main plant stem or above a leaf of another flower stem. Deadheading reallocates energy from creating seeds to producing more flowers elsewhere on the plant.

Fertilize cosmos with a balanced, water-soluble fertilizer, such as 10-10-10, every two-to-four weeks. If the garden soil is already fertile and enriched with compost or manure, the need for fertilizing is diminished. Water-soluble fertilizer may be applied in tandem with a regular watering from a sprinkling can to keep the soil from becoming too dry.

Continue to deadhead, water and fertilize the orange cosmos up until the first autumn frost, which kills the plants. Harvest any developing seed heads once frost hits since you can save the seeds over the winter indoors in a paper envelope and sow them again next spring.