Growing yams in the home garden requires a long, hot growing season to give these large tubers time to fully develop. One of the best tips for planting yams is to start them from slips early in the spring on mounds to facilitate soil warming and drainage. Yams require 95 to 110 days of warm, frost-free weather to produce a good crop from slips.
True yams, and the sweet potatoes commonly called yams, are similar but unrelated tuberous vegetable crops. True yams are grown in a limited range in the tropical world. The yams commonly found in the vegetable bins at grocery stores and in the home garden, are actually orange, moist-fleshed varieties of sweet potatoes. For all intents and purposes, these are referred to as yams both by grocers and vegetable growers.
One of the best tips for growing yams is to start with slips. Slips are vegetatively propagated yam-plant starts. These can be found at nurseries, from seed suppliers and at local markets in the spring when the vegetable seedlings start to show up. It is best to buy the slips from a reputable grower to avoid inadvertently buying diseased root stock.
Yams grow best in light, loamy soil with good drainage. A slightly acidic pH between 5.0 and 6.5 is ideal for this tuberous vegetable crop. Heavy clay soil is not recommended, as it causes the yams to grow long and stringy rather than plump and soft. The top 6 to 8 inches (about 15 to 20 cm) of soil should be turned over seven to 14 days before planting.
Another good tip for growing yams is to create ridges 8 inches (about 20 cm) high for planting. The raised soil warms up faster in the spring, and it doesn't get too wet during the spring rains. Yams are particularly susceptible to wet, cold soil. A 5-10-5 or a 10-10-10 fertilizer can be added to the soil before planting. A second application of the same fertilizer can be applied as soon as new growth starts.
When growing yams, slips should be planted outside three to four weeks after the last frost date. If they are planted too soon, these cold-sensitive plants are likely to perish in the soil. The slips should be planted so the bottom 3 to 4 inches (about 7 to 10 cm) is below the soil line. A plant spacing of 9 to 18 inches (about 22 to 45 cm) apart along the ridge gives the plants room to grow and mature.