Set plants in a dry, warm soil, spaced 12 to 18 inches apart, depending on the ultimate spread of the species you’ve chosen. Ample humus content and rather low fertility are best; choose a soil with excellent drainage as well.
Clip or prune in spring, before the new growth starts, to promote bushiness and maintain desired height and form. Trim off flower stems after bloom in late summer. This is also a good time to trim back the foliage again, if desired, to develop a more compact bush.