Water garden cosmos regularly, especially during dry spells, ensuring the soil is consistently moist but not waterlogged. Allow the top inch of soil to dry out slightly between waterings.

Reduce watering frequency in cooler weather or if the plant is in a pot that retains moisture well.

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

Light pruning can also help maintain plant shape and remove any leggy or damaged stems, improving overall appearance and vigor.

Garden cosmos are easily grown from seed, sown directly outdoors after the last frost or started indoors a few weeks prior. Seeds germinate readily in well-drained soil.

They can also be propagated by cuttings taken from non-flowering shoots in early summer.

Repotting is generally not necessary for annual garden cosmos as they are typically grown as bedding plants or in the ground. If grown in containers, repotting can be done in spring before new growth begins if the plant becomes root-bound, using a slightly larger pot with fresh potting mix.