After the first year or so, rosemary requires little to no water. You don’t have to prune rosemary, but might want to shape it in early spring every few years. Try not to prune away more than one-third of stems and avoid cutting into the woody branches when possible.
Although few problems affect rosemary plants, the spittle bug can take up residence on the stems. The covering over the bug looks like pieces of cotton or meringue on stems. Just spray them off with a hose. Winter snow can damage rosemary with the slow, cold melting that dampens the plants over cool ground.
There are two types, or growth forms, of rosemary. The plant can grow as a shrub, which can be trimmed into shapes, or as a low-growing groundcover that can cascade over rock walls. Just check your local nursery for one that can handle your cold or heat. Rosemary loves sun, but can do well in partial shade.
Plant rosemary in loose, well-draining soil. In cooler climates, tuck the plant against a south-facing wall or protected rocky area to help warm it in winter. Rosemary might do better in containers in hotter Southwest climates, where you can move the plant around for a little more shade in peak summer heat. In colder areas, container-grown rosemary might get too cold to survive.