Yams are not only delicious, they are packed with nutrients. Even though yams are a warm weather crop--they originated in Africa--it is possible to grow them in northern climates where the growing seasons are short. Most varieties of yams need 120 days to produce a good crop, so starting them early in the season is essential. Growing a yam in northern climates may result in smaller yields and root size, but you will still achieve a crop. There is nothing better than digging yams from the garden and serving them for dinner.
Plant the sweet potato tuber or slips. To produce slips, fill a tray with potting soil one month before you are to plant them outdoors. Place the potato root horizontally in the tray and cover with 2 inches of moist sand. Keep the tray in a place that stays between 23.9 and 26.7 degrees Celsius. Remove the sprouts when they are 4 to 6 inches long. You can then plant the slip right into the ground, or put it in a glass of water, so roots will form.
Plant the rooted slips into 4-inch pots filled with well-draining potting soil. This will give them a more time to grow before you plant them in the ground if the weather is still too cold outdoors.
Prepare the growing bed in May. Yams like well-drained loamy to sandy soil, so you should add 2 inches of compost over the top of the soil. Dig or till that into the garden.
Place black plastic over tightly over the ground. This will warm the ground and expand the season by a few weeks. Put heavy rocks or bricks over the top to keep the wind from blowing the plastic away.
Cut a hole into the black plastic and plant the yam slips. Space the tubers a foot apart and space each row 3 to 4 feet apart.
Fertilise the yams. If you think your soil is not the best, fertilise the yams at time of planting, then again after six weeks, and one more time at 12 weeks. Do not feed them a fertiliser that is high in nitrogen. If you do, all you will get are great looking yams with lots of leaves, but nothing underneath the plant
Water the freshly planted slips regularly. After that you don't need to water that much unless the soil becomes really dry. Yams can grow with little water once they become established.
Dig the yams as late in the season as possible, preferably right before the hard frost. Another sign of when to dig the yams is before the soil temperature falls below 15.6 degrees Celsius.
You may want to test some of your soil. to make sure it has the right pH content of 5.5 to 6.5. For easier harvest, mow or remove the vines before you dig. You can grow yams from the grocery store, but they may not have a short growing season that you need.