An herb named for its use in soap-making, this late spring- and summer-blooming perennial groundcover reaches 1 to 3 feet in height. Sow seeds directly into the garden in a sunny spot in spring, and deadhead plants regularly. For a fun project, make liquid soap by simmering 1 cup of tightly packed chopped leaves and stems in 2 cups of water for 15 minutes. Strain through cheesecloth, and pour into a glass jar. Soap lasts for about a week in the fridge.