Several types of Dioscoreaceae plants are known as the "yam." In North American grocery stores, some types of sweet potatoes are also known as yams. Whether it's a true yam or a sweet potato, both types of plants have similar needs and can be grown for a bounty of sweet-tasting, starchy root vegetables. Create a mounded garden in your backyard to make harvesting the yams easier once it's time to reap the rewards of your labor.
Prepare the soil. Clear away all surface vegetation and debris like sticks and large rocks. Use a spade--or a mechanical tiller if you're creating a large yam garden--and breakup the soil to a depth of 10 to 15 inches.
Mix in 3 to 4 inches of garden compost to amend the soil. Alternatively, you can use standard vegetable garden fertilizer applied according to the fertilizer's label since potency varies by brand and product.
Create a mound of soil. The mound should be approximately 10 inches tall and 24 inches to 36 inches across. If you're making more than one mound, space each mound apart by 2 to 3 feet.
Plant the yam tuber. Bury the tuber in the center of each mound, approximately 2 inches below the surface of the soil.
Water the mounds to a depth of 12 inches--you can check the depth of moisture by inserting a stick, rod or pencil in into the mound--twice a day. The buried tuber will sprout and break the surface of the mound within a few weeks.
Fertilize the yam plant every three to four weeks to encourage healthy root production. Add a liquid or granular fertilizer with a low level of nitrogen--nitrogen promotes foliage growth, which is not what you want with this root vegetable--and a high amount of phosphorous. Example nutrient ratios include 6-24-24 and 8-24-24 fertilizers. Apply according to the product's label.
Harvest the yams within three to four months of the plant sprouting. Use your hands and flatten the mound to expose the yam plant's underground tubers. Alternatively, insert a pitchfork at the bottom of the mound and lift upward to uproot and reveal the yams.