Prepare a planting location ahead of time by spading the soil to a depth of 12 to 15 inches. Dig in 2 to 4 inches of compost or decomposed manure.
Dig up the clump of catmint that you want to move. Insert a shovel into the ground about 6 inches from the center of the plant, and then loosen the roots by digging around the circumference. When the roots are loose, dig deep and lift the plant from the ground.
Dig a hole as deep as the plant's root ball and about twice as wide. Place the catmint in the hole with the top of the root ball even with the surrounding ground. Fill the hole with soil and pat the ground lightly with the back of your shovel to remove air pockets.
Water the plant deeply to saturate the roots to a depth of 6 to 8 inches, then continue to water every other day until the plant shows new growth -- usually two to three weeks. Thereafter, water about twice every month, but only if the soil is dry.
Spread about 1 inch of mulch, such as chopped bark or pine needles, around the plant to conserve soil moisture and suppress weed growth. Don't allow the mulch to pile up on the plant.