Water tropical horseweed regularly, keeping the soil consistently moist but not waterlogged. Allow the top inch of soil to dry out slightly between waterings. In hot, dry weather, more frequent watering may be necessary.

Reduce watering during cooler, dormant periods.

Prune tropical horseweed to maintain its shape and encourage bushier growth. Pinch back the tips of young stems to promote branching. Remove spent flower stalks to prevent self-seeding and prolong blooming.

Pruning is best done in spring or early summer.

Tropical horseweed is easily propagated by seeds or stem cuttings. Sow seeds directly outdoors in spring after the last frost, or start them indoors a few weeks prior.

Take stem cuttings in late spring or early summer, root them in moist soil or water, and transplant once established.

Repot tropical horseweed when it becomes root-bound, typically every one to two years. Choose a pot that is slightly larger than the current one. Use a well-draining potting mix.

Repot in spring before new growth begins to minimize stress on the plant.