Water Splitlip Hempnettle regularly, especially during dry periods, to keep the soil consistently moist but not waterlogged. Allow the top layer of soil to dry slightly between waterings.

Reduce watering in cooler months when the plant's growth slows down. Good drainage is crucial to prevent root rot.

Prune Splitlip Hempnettle to maintain a bushy shape and encourage more blooms. Deadhead spent flowers regularly to prevent self-seeding if unwanted.

Light pinching back of young plants promotes a more compact growth habit. Trim back leggy stems in mid-summer.

Splitlip Hempnettle is easily propagated by seed. Sow seeds directly outdoors in spring or fall where they are to grow. They can also be started indoors a few weeks before the last frost.

Division of established clumps in spring or fall is another effective method.

Repotting is generally not necessary for Splitlip Hempnettle, as it is often grown as an annual or short-lived perennial and may self-seed.

If growing in a container and it becomes root-bound, repot into a slightly larger container in spring before active growth begins. Ensure good drainage.