Water regularly, allowing the soil to dry out slightly between waterings. Southwestern Cosmos prefers well-drained soil and is drought-tolerant once established. Avoid overwatering, which can lead to root rot.

Reduce watering frequency during cooler months or when the plant is dormant.

Pinch back young plants to encourage bushier growth. Deadhead spent flowers regularly to promote continuous blooming and prevent self-seeding.

Light pruning can be done in early spring to shape the plant and remove any dead or damaged stems from the previous season.

Southwestern Cosmos is easily propagated from seed. Sow seeds directly outdoors in spring after the last frost, or start them indoors a few weeks prior. Seeds germinate best in well-drained soil with light exposure.

Cuttings can also be taken from young, non-flowering shoots in late spring.

Repot young plants as needed, typically when they become root-bound, usually every one to two years. Choose a pot that is only slightly larger than the current one, ensuring good drainage.

Use a well-draining potting mix. Repotting is best done in spring before active growth begins.