Farm and Garden: Growing Sweet Potatoes in Iowa

AMES, Iowa – The Sweet Potato (Ipomoea batatas) belongs to the morning glory family (Convolvulaceae). While typically considered a vegetable for kitchen gardens in the southern United States, the sweet potato is a vegetable that can thrive in Iowa’s hot and humid summers. In this week’s Yard and Garden article, gardeners from the Iowa State University Extension and Outreach answer questions about growing sweet potatoes.

Is there a difference between sweet potato and yam?

Yes, they are different. Yam is a monocot (monocot), dry and starchy rough skin cultivated for its tuber, native to West Africa and belonging to the Dioscoreaceae family. The sweet potato, on the other hand, is a dicot (two cotyledons), moist and sweet, with a smooth skin, grown for its roots, native to Central/South America and belonging to the Convolvulaceae family.

What are optimal growing conditions for sweet potatoes?

Sweet potatoes are a warm-season crop that requires a long, frost-free growing season to mature. Plants require full sunlight and should receive at least six to eight hours of full sun each day. Sweet potato plants unravel and drag along the ground. Well-drained, sandy or loamy soils are best for sweet potatoes. Heavy clay or rocky soils will result in deformed sweet potato roots. Soil that doesn’t drain well can result in lower yields or root rot. Sweet potatoes tolerate a wide range of soil pH, but grow best in soil with a pH of 6.0 to 7.0.

What is the planting material for sweet potatoes?

Sweet potatoes are grown from a vegetative stem tip cutting, also known as a “slip,” propagated from the roots of the previous season’s crop. Briefs should be disease and insect free and purchased from reputable suppliers. A good sweet potato slip should be firm, green, and 8 to 12 inches long, preferably with one or two leaves. Notes may or may not have roots when cut.

How do you properly plant sweet potatoes?

Plant in mid to late May or early June after all danger of frost has passed. Because the sweet potato is a vine plant and prefers to spread, the plant scoots in rows 36-48 inches apart. Plant spacing within the row should be 12 inches. Row spacing greater than 12 inches results in a higher proportion of jumbo-sized roots at harvest, which are difficult to manage and process. Less than 12 inches of row spacing results in a higher proportion of smaller and slender roots, which are also undesirable. Sweet Potato Slips.

How do I care for sweet potatoes?

Before planting, apply 1 to 2 pounds of an all-purpose garden fertilizer such as 10-10-10 per 100 square feet. At the time of vine growing, sprinkle an additional 1 to 2 pounds of an all-purpose garden fertilizer around each plant. Keep plantings weed-free early in the season, after which the sweet potato’s vining nature will naturally smother and suppress many weeds. Provide consistent watering for most of the growing season; However, do not keep the root zone moist all the time. It is better to limit water in the last four weeks before harvest to protect the developing roots from cracking.

What Are Some Good Sweet Potato Varieties for Iowa?

There are several sweet potato varieties available to home gardeners. These varieties vary in color, size and sometimes in shape. In terms of color, there are varieties with light orange, yellow or even white flesh color. Varieties suitable for Iowa include Beauregard, Centennial, Covington, Evangeline, Georgia Jet, and Jewell.

When and how do I harvest sweet potatoes?

Sweet potato varieties vary in days to maturity, but most are between 90 and 120 days. Typically, they are harvested in late summer/early fall, before soil temperatures drop below 60 degrees Fahrenheit. You can wait until the variety is ripe (90-120 days) or harvest right after the first frost. There is no rush to harvest before the first frost, but exposing the root to colder soils for long periods is not recommended. Cool soil reduces root quality and shelf life. Harvest by carefully digging around the plants with a spade fork or shovel without damaging the roots.

How do I pickle and store sweet potatoes?

Sweet potato roots need to be cured to reduce cuts, bruises, and rot, and convert some of the starch in the roots to sugar. Commercial growers dry their sweet potatoes in special rooms at 85°F and 80% to 90% relative humidity for seven to 10 days. Duplicating this process would be very difficult for home gardeners. A middle ground would be to air dry sweet potatoes in a warm and shady place like a garage for 10-14 days. Once cured, the roots should be stored in a dark, cool place with temperatures between 50 to 55 F. Sweet potatoes can be stored for four to six months in good conditions.

Shareable photo: 1. Harvested sweet potato. 2. Sweet potato plants.

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