Fill the cells of a seed starting tray with potting soil seven to eight weeks before the last frost date in the area. Insert one seed into each cell, just covering them with soil. Water until the soil settles.
Set the seed tray in a warm, sunny spot. If you do not have a warm window, set the tray on a germinating heating mat.
Keep the soil moist to the touch by watering whenever it begins to dry out. The seeds will germinate in one to two weeks. In the meantime, select a garden location for the seedlings that gets full sun and has well-draining soil.
Remove the weeds in the planting site. Cover the soil with 2 inches of compost and till it into the soil to a depth of 8 inches. Two weeks after the last frost, dig planting holes that are spaced two to three feet apart and are twice as big as the seed cells.
Lower one ground cherry plant into each hole. Firm the soil and water until it settles. Spread a 1- to 2-inch layer of mulch around the base of each plant to keep down weeds.
Water the ground cherries at a rate of 2 inches per week, or less if you get sufficient rainfall. They will be ready for harvest in late summer, once the husks brown and drop to the ground.