Grow A Sweet Potato vine
by John Harmon
October 3, 1999

If you had any doubt that summer is over the minus nine degrees C. on Monday morning should have been enough to chinch it. The fresh snow on all the mountains around Whitehorse was also a dead giveaway. Time to switch the gardening to indoors for another season.

I got an e-mail request from a schoolteacher for information about growing sweet potatoes in the classroom. It's a great way for kids to see the entire process from the formation of roots to the first leaves forming.

For the classical method you will need a jar full of water, four toothpicks and a sweet potato. Push the toothpicks into the middle of the potato forming a cross on which the potato will be supported in the jar.

Place the jar in a dark warm spot until it starts growing then bring it out into the light. Be sure to keep the jar filled with water and change it every few days. If the water is left too long the roots will be starved for oxygen and you can get some nasty scum growing. You will get better results if you use water that doesn't have chlorine or fluoride in it. If you have to use city tap water let it sit in an open container for 24 hours so the chlorine can evaporate. Very soon you should soon have a nice vine growing.

You can also grow them in containers and harvest your own tubers. The sweet potato, a member of the morning glory plant family, is native to tropical America. Keep the word "tropical" in mind. Sweet potatoes require a long, warm growing season of at least five months, so they are best grown indoors here in the north. They do not grow well below 70 degrees Fahrenheit so if you heat with wood and the temperature drops down at night you'll need more than five months to get a crop. The plant needs a nighttime temperature of 60 degrees Fahrenheit

Sweet potatoes are not grown from seed. Plants may be purchased from a greenhouse or garden center if you live in the south or propagated from the tubers themselves in a hot bed heated with an electric cable. The cable should be covered with one inch of sand. Tubers are then covered with four inches of sand, kept at 80-85 degrees Fahrenheit for three to four weeks until sprouts appear. The thermostat is then lowered to 70 degrees Fahrenheit. Twist the slips from the sweet potato and replant in your container. If you don't have a heating cable you can use the same method and keep them where it's as warm as possible. Allow six weeks between the time the tubers are first bedded and transplants are set in the container. Longer without a heating cable.

Sweet potatoes should be planted in a container at least a foot in diameter to allow room for the roots. A five gallon plastic bucket is big enough. The sweet potato grows best in pH of 5.5 to 6.5. Use a porous soil mix to provide good drainage and allow for root expansion. Transplants should be kept moist until they are well established. Feed them weekly and provide as much light as possible. The more light they get the faster you will have tubers to harvest. The plants should be started on grow nutrient and changed to root nutrient when the tops are about 6" high. Trace minerals are important. Some of the flavor in sweet potatoes is apparently due to trace minerals so use a plant food that is complete. This plant is a vine and can be trained on a trellis.

Sweet potatoes may be harvested as soon as the roots reach eating size. If your vines become frosted the tubers should be dug immediately as decay in dead vines passes down to the tubers. Protect them from the cold. Sweet potatoes should not be allowed to become chilled in cold soil or after they are dug. Temperatures below 55 degrees F. may be damaging. That alone kind of eliminates the possibility of growing them outside in the north even if we had the frost free days.

Sweet potatoes may be boiled, baked, fried, or candied. They have high food value. Varieties with deeply yellow colored roots are a good source of vitamin A but if you're interested in taste and can stand the calories here's a recipe for the pie from the kitchen of Dora Grimm.

Sweet Potato Pie. Makes 2 - 8" pies or 1- 9" deep dish pie.

pastry for 1 crust pie
1-1/2 cups sugar
3 eggs
1-1/2 cup mashed sweet potato
1 teaspoon vanilla flavoring
1 stick butter
1 small can evaporated milk (2/3 cup)

Cream eggs and sugar. Add sweet potato, vanilla flavoring and melted butter. Last, add milk. Mix well. Put in unbaked pie shell. Bake for 1 hour at 350 degrees Fahrenheit.

Even if you don't get tubers of eating size the sweet potato makes an attractive tropical plant and in the end a great pie.

John Harmon owns and operates Tropicals North. Write to John at The Real Dirt, c\o 211 Wood St., Whitehorse, YT., Y1A 2E4 or e-mail this

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