Sweet Potatoes

Source: [1]

Years grown at UBC Farm/LFSOG: Not available

Common names: Kumara, Louisiana Yam, Yellow Yam.

Varieties:There are three categories to classify the 100’s of different varieties of sweet potatoes and these three categories are: dry and mealy fleshed, soft and moist fleshed, and coarse fleshed (used as animal feed). White or pale types are floury with a chestnut-caremel flavor, while yellow and orange varieties are sweet and watery.

Growing conditions

Propagation: Take cuttings from healthy shoots 8-10in. long from below a leaf joint, removing basal leaves. Alternatively pack numerous healthy tubers in a tray of moist potting mis and sharp sand, vermiculite or perilite and place in a warm greenhouse or hotbed. With shoots 9-12in. long, cut them off 2in. above the soil and take the cuttings as described above. ( 3 potatoes roughly produce 24 cuttings, enough for a 25-ft. row.) Plant the cuttings about 3-4.5 ft. apart, leaving half the stem exposed. Instead of cuttings, planting small tubers 3-4in. deep along the top of a ridge on sandy, free draining soil on level ground.

Sweet potatoes’ optimal growing conditions are in tropical or subtropical climates where temperatures reach 70-77°F. Leaves and tubers can be damaged or killed by light frosts. Annual rainfall of 30-50 in. is ideal, with wet weather in the growing period and dry conditions for the tubers to ripen. The tuber production is fastest and sugar production highest when day length exceeds 14 hours. Ideal soil conditions are to be moisture-retentive and free-draining with a pH of 5.5-6.5. If necessary, well-rotted organic material can be dug in before planting and watering is rarely needed if planted at the start of the rainy season. Stem development rather than tubers are encouraged with excess nitrogen. Once established, distribute a high-potash granular fertilizer around plants and occasionally lift vines from the ground- this will prevent rooting at the leaf joints. Be sure to rotate crops.

Protection:: Grow undercover in a cool temperature zone where the minimum temperature is 77°F. Take cuttings from healthy shoots of mature plants and insert around 4 cuttings around the outside of a 6-in. pot and fill with potting mix. Maintain moisture with tepid water and regular misting once the cuttings have been transplant into a greenhouse, provided a good root system has formed. Prune stems to be 24 in. at the longest; this will encourage side-shoots and also, from late winter, aid in congested growth.

With Container Growing, grow in pots or containers 12in. deep and 15in. wide along with loam-based potting mix and moderate fertilizer levels. Use supports.

Storage

Provided the conditions are good, tubers will ripen in 4-5 months. When slightly immature or until waiting till vines begin to yellow, lift the tubers carefully and avoid bruising. Either use fresh to store once dried in a cool dark place for up to a week.

Pests & Diseases:

Leaves can suffer from leaf spot and sooty mold; black rot appears at the base of the stem where brown rot appears at the tuber so be sure to check stored tubers regularly; susceptible to white fly or red spider mite when under cover.

Seasonality

Maintenance by season is important to ensure crop vitality.

Spring: take cuttings under cover, keep warm and moist.
Summer: keep cuttings weed-free, water well, feed, and prune as necessary.
Fall: Harvest. Save some tubers for the next crop.
Winter: keep compost slightly moist.

Nutritional Information

Nutrition Facts/Valeur Nutritive
Serving Size: 250mL cubes (141 g)
Amount Per Serving	%Daily Value*
Calories 121
Total Fat 0.1g	0%
Saturated Fat 0g	0%
Trans Fat 0g
Cholesterol 0mg	0%
Sodium 75mg	3%
Total Carbohydrate 28g	9%
Dietary Fiber 4g	16%
Sugars 6g
Protein 2g
Vitamine A	100%
Vitamine C	6%
Calcium	4%
Iron	6%
* % Daily value based on a 2000 calorie diet

Nutrient data from the Canadian Nutrient File

Healing properties: antioxidant-rich and anti-inflammatory ridding body of free radicals that cause cancer and heart disease, excellent source of Vitamin A (in the form of beta-carotene), very good source of Vitamin C and manganese.

Concerns: contain oxalates in small numbers yet are measurable enough to suggest avoiding if one has existing kidney or gallbladder problems. Oxalates can also disrupt calcium absorption

Recipes

Sweet Potato Apple Cake (Serves 9)

Sweet potatoes and apples add moistness and natural sweetness to this simple cake.

Ingredients

Natural cooking spray  
1 cup whole wheat pastry flour
1 teaspoon baking soda
1/2 teaspoon salt  
1/2 teaspoon ground cinnamon  
1 teaspoon ground nutmeg  
1/2 cup brown sugar  
1 egg  
1 large apple, peeled, cored and grated  
1 (3/4-pound) sweet potato, peeled and grated  
1 teaspoon vanilla extract
1/2 cup chopped walnuts

Method

Preheat oven to 350°F. Lightly oil an (8-inch) baking pan with cooking spray; set aside.   In a large bowl, whisk together flour, baking soda, salt, cinnamon and nutmeg; set aside. In a second large bowl, whisk together sugar and egg until well combined. Stir in apple, sweet potato, vanilla and walnuts and then add apple mixture to flour mixture and stir to combine.   Transfer batter to prepared pan and bake until cake pulls away from the edges and is deep golden brown, 40 to 50 minutes. Set aside to let cool and then cut into squares and serve.

Sweet potato dhal (from Agora manager Laura Hsu)

Ingredients

12 Tbsp vegetable oil
6 large yellow onions
9 cups of red lentils
4 tsp tumeric
6 medium sweet potatoes, diced into 1 inch cubes
6 jalapenos, minced
1 bunch of cilantro
3 28 oz cans of tomato or 8 fresh tomatoes
10 cups water

Method

Saute onions, with oil until golden.
Boil lentils for 30 minutes
Add sweet potato, turmeric, jalapeno, and tomatoes boil (at simmer) until potatoes are tender
Add cilantro and serve

Additional usage inventory

Medicinal: Antibacterial and fungicidal substances are found in sweet potatoes and their leaves which are used in folk medicine.

Preparation Tips: If purchasing organically grown, you can eat the whole tuber:flesh and skin; if peeling, you should cook immediately to prevent darkening upon contact with air; there are nutritional advantages to roasting over boiling.

Academic connections

Information not available

References

Biggs, M., McVicar, J., & Flowerdew, B. (2006). Vegetables, herbs, and fruit: An illustrated encyclopedia. Buffalo, NY: Firefly Books

Health Canada. (2008). Canadian Nutrient File (CNF). Retrieved from http://webprod.hc-sc.gc.ca/cnf-fce/index-eng.jsp

Additional notes

In Shakespeare’s day, sweet potatoes were sold in crystallized slices with sea holly as an (“eringo”) aphrodisiac. In, The Merry Wives of Windsor, Falstaff cries: “let the sky rain potatoes…hail kissing comforts and snow eringoes.”