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Sweet potatoes are sugary, delicious vegetables that will do well in Utah, if the growing season is long and hot enough. They thrive in heat. Instead of being a type of potato, they are actually a member of the morning glory family. Simply, the tubers form from the thickened root up the vine. Sweet potatoes are easy to grow, great for storage, and high in vitamin content. Enjoy them mashed, baked, as french fries, or even pies; a staple for the Thanksgiving table.
Soil Preparation
Sweet Potatoes prefer a sandy soil, rich in organic matter, well drained, and not too heavy. They also need full sun exposure. Before planting, incorporate 1-2 inches of well composted organic matter, Humic, and 1 lb. of all-purpose fertilizer (we recommend “That’s all it Takes” complete fertilizer or Happy Frog Organic Tomato & Vegetable Food) per 100 square feet and work them in to a depth of 4-6 inches. Heavy, clay-based soils must be amended with compost and organic matter to encourage and allow for good root development. For best results, add 2-4 inches of a variety of different types of organic matter and 50 lbs. of Zeolite soil conditioner per 100 square feet each fall for multiple years to increase drainage and nutrient availability. By doing this yearly, over time you can create a better growing environment for your garden plants to thrive in and produce. Please consult our Soil Preparation Guide in the attached appendix.
Planting
Sweet potatoes do NOT like the cold. Frost and even close to freezing temperatures are their greatest enemy. Plant the starts or slips after the danger of frost has passed (for Cache Valley that’s about Mother’s Day). Select an area with sunlight, fertile soil, and good drainage. Hill up the soil to 6-8 inches high and 12 inches wide when you’re planting 2-3 weeks before you plan to plant the slips. For increased soil temperature use black or clear plastic or weed barrier after hilling the soil to solarize the planting area; it will increase your soil temperatures (and your success) by up to 15°. When planting the slips, use ¼ cup of Hi-Yield Bone meal, a phosphorus based fertilizer, for every 4-6 ft of row and work it into the soil, to encourage large tubers. Dig down about 4-6 inches and plant the roots completely in the soil, being very gentle. Plant them 2 ft apart in rows 4-6 ft apart. The vines will sprawl, so give them plenty of room. The slips can even be planted in a pot at least 18 inches deep and wide. Water thoroughly after planting with Kangaroots root stimulator to prevent transplant shock and to encourage quick root development. Water the transplants when needed with the Kangaroots and Fungicide 5 for the first 2-3 waterings to ensure their early establishment and development. It really does make that much difference.
Varieties
Sweet potatoes are categorized into two types: firm flesh and soft flesh. The soft flesh tend to have a sweeter taste w/orange flesh. They are sometimes incorrectly called yams. Firm flesh tend to keep a bit longer and have more of a tint of purple to their skin. Because of our short growing season, in Cache Valley, not terribly conducive to growing sweet potatoes, we only carry a few varieties: the soft flesh Beauregard (dark,orange flesh, sweet taste) and Georgia jet (orange flesh, red-purple). Gardeners have had success growing other varieties, but we have had the best success with these two specifically.
Water
Sweet Potatoes require frequent watering during the early part of the season, usually about 1-2 inches per week in 2-3 applications. Use drip or soaker irrigation if possible, and mulch heavily around the plants with an organic mulch to help retain soil moisture and to prevent weed emergence. We can’t stress enough the importance of using plastic mulch or weed barrier around the plants to prevent weeds, to heat up the soil, and to prevent damage from rapid drying and moisture loss. You will see a dramatic increase in your yields because of it. Once the plants begin maturing and the tubers start developing more size, decrease the water to avoid root rot in the tubers. Sweet potatoes are fairly drought tolerant, but consistent moisture will help increase your yield.
Fertilizer
About 4-6 weeks after transplanting, apply a balanced vegetable food (“That’s All it Takes” or Happy Frog Organic Tomato & Vegetable Food ) around the base of the plants and water thoroughly. Use about 1/4 cup per vine. For some quick growth, especially around the time they start to flower and set fruit, use Ferti-lome Blooming and Rooting water soluble fertilizer or an organic alternative like Seedlinger’s Universal Plant Food weekly to kick them into fruit production mode. Since Sweet Potatoes are more temperamental and cold susceptible, we always recommend an application of beneficial microbes and mycorrhizae (Kangaroots or Myke supplements) to help with their development. Your plants will be healthier, more vigorous, and produce fruits faster and for a much longer harvest.
Common Problems
Sweet potatoes tend to be relatively pest free, making them easy to maintain. Flea beetles will lay their eggs in the spring and the maggots will then feed on the developing roots. Aphids and leafhoppers will attack the plants. Use Ferti-lome’s Triple Action Insecticide to kill the adults and/or Fertilome Spinosad to eliminate the adults and larvae. Root rot can also be potentially harmful to the sweet potatoes. Too much water can cause the tubers to rot. Don’t plant sweet potatoes in the same place, two years in a row to eliminate the possibility of carrying over diseases from year to year. Also, don’t forget that the deer love mature sweet potato vines and tubers-take the necessary steps to protect your plants with netting or repellent.
Harvest
When the tubers below the surface are ready to be harvested, the foliage will turn yellow and slightly fall over. Sweet potatoes do not like the cold, so if it freezes the tops, harvest the potatoes immediately. Carefully dig the tubers, making sure not to bruise or scrape them with the spade. Let the potatoes cure for 1-2 weeks in 70-80 degrees for maximum storage life. When putting them in storage, keep them in a cool (50 degrees), dark, dry place. Each plant will yield about 2-3 lbs. or more of roots, so enjoy!