Cut tubers into several pieces in spring, making sure each piece contains a bud or “eye.” The upper tip of the tuber is the most viable part and is called a “sett.”
Allow your cut pieces to cure for one to two days before you plant them to prevent rotting in the ground. Dip the cut portion of each sett in wood ash if you wish, which helps the curing process. Store the pieces in a warm, dark, dry and well-ventilated area.
Prepare a planting area in full sun. Select an area that is relatively free of rocks. Amend the soil with organic compost and other organic materials, such as fallen leaves, grass clippings and chopped plant parts. Spread a 2- to 3-inch layer of organic material on the soil surface, and then mix it into your soil with your shovel. If you will be planting more than one row of purple yams, space the rows about 4 feet apart.
Make planting holes about 6 inches deep and 10 to 12 inches apart. Drop one of your cut pieces into each hole, and fill with the soil mixed with organic materials.
Build up your rows after plants begin to grow. Shovel soil from the areas to either side of each row, and pile it on top of the row.
Fertilize your yams with a plant food containing equal amounts of nitrogen, phosphorus and potassium. Fertilize when you first plant your yams, six weeks after that and again 12 weeks later. Yams also benefit from the addition of mirconutrients such as calcium, magnesium, sulfur, boron, chlorine, copper, manganese, molybdenum and zinc.