Sweet, Sweet Potatoes

While white or Irish potatoes are certainly more widely grown and eaten, sweet potatoes also deserve a place in your garden and at your table. They thrive in summer's heat and take little care to produce large, sweet tubers.

Homegrown sweet potatoes are not only loaded with great flavor, they also are healthful. Sweet potatoes are an excellent source of vitamin A, vitamin C, and manganese, and a good source of copper, dietary fiber, vitamin B6, potassium, and iron. They also contain proteins with antioxidant properties.

As the summer heat builds, consider growing a bed of sweet potatoes, even if you live in the North. The roots you harvest will feed you right into winter.

Unlike most other vegetables, sweet potatoes are grown from small plants or "slips", not seeds. Slips are cuttings taken from sweet potatoes grown the previous year. These certified disease-free slips can be purchased locally or through the mail.

Sweet potato varieties are grouped by moist or dry flesh. Most people prefer the moist-fleshed varieties for their sweet flavor. Contrary to popular belief, orange moist-fleshed sweet potatoes are not yams. They received that name as a way to distinguish them from white-fleshed sweet potatoes. Yams are a different tropical root that's rarely seen in our markets.

While sweet potatoes are traditionally grown in the hot, humid Southeast, some varieties are adapted to shorter growing seasons and are good choices for Northern gardeners. Sweet potatoes are also grouped as bush or vining types, depending on their growth habit.

Here are some of the best varieties to grow. All are moist-fleshed types unless otherwise indicated.

'Beauregard' is a vining variety that matures in 90 days from transplanting and has very little cracking. The rose-colored skin gives way to orange flesh.

'Bunch Porto Rican' is a bush type that has light yellow skin, cream- and orange-colored flesh, and attractive purple stems. It matures in 100-110 days.

'Georgia Jet' is a vining type that matures in only 80 days, making it a great Northern variety. It has rose-colored skin and dark red flesh.

'Nancy Hall' is an old-fashioned vining type with pale flesh and brown skin that matures in 110 days. It's sweet and tasty.

'Vardeman' is a bush type that has stringless, orange flesh and dark orange skin. The purple and green leaves make this an attractive plant even in a flower garden. It matures in 100 days.

'White Triumph' is a vining type with white skin and dry, white flesh. It matures in 100 days.

For more sweet potato varieties, go here .

Sweet potatoes need four months of frost-free, warm temperatures to mature. Before planting, amend the soil with compost and till to a depth of 10 inches. Add a fertilizer high in phosphorus if your soil is low in that nutrient. Phosphorus is critical for root and tuber growth. Unless growing in sandy soil, build a raised bed and create a 6-inch-deep furrow for the slips.

Once the nights are above 55 degrees F, set the slips in the furrow 12 inches apart. Plant them to the depth of the first leaves. Make a shallow depression around the plant to collect water. Keep the beds well watered.

In Northern areas, consider laying black plastic over the beds to preheat the soil, and plant the slips in holes in the plastic.

Sweet potatoes make an excellent ground cover so give them plenty of space to run. Even the bush varieties will want to stretch out a bit. Keep the bed well weeded. In warm areas, mulch the plants with straw after the plants are well established (about one month after planting).

On poor fertility soils, side-dress the plants with a balanced fertilizer about three to four weeks after planting.

Harvest sweet potatoes before frost. In warm areas, that usually is in October or November. In Northern areas, it may be as early as September. The vines are very frost sensitive and will die when exposed to any cold weather.

Recently harvested sweet potatoes are loaded with starch and carbohydrates. They need time to cure to develop the sugars that make them taste so sweet. Curing also allows the tubers to heal any wounds so they will last longer in storage. Dig sweet potato tubers carefully, trying not to bruise or damage them. Store in a warm (80 degrees F), humid location away from light for about 7 days to cure.

Once cured, place them in a cool (55 degrees F), humid location in wooden bins for long-term storage. Most varieties will last four to seven months in storage.

White Mold on Beans

Q. My bush beans are starting to produce but some of the fruits are turning slimy and have a white mold growing on them. What should I do?

A. It sounds like your beans have white mold disease. The fungus that causes this problem requires moisture to grow, so a wet spring and early summer will exacerbate the problem.

To prevent the problem, stay out of the bean patch when the foliage is wet, as you can easily spread the disease. Rotate your bean crops, avoiding planting legumes in that area for three years.

To stop the spread of the disease, cull infected plants, thin bean plants so individual plants are spaced wider apart, cultivate frequently around plants to dry out the soil, and don't use organic mulch on the rows between plants.

About Charlie Nardozzi

Charlie Nardozzi is an award winning, nationally recognized garden writer, speaker, radio, and television personality. He has worked for more than 30 years bringing expert gardening information to home gardeners through radio, television, talks, tours, on-line, and the printed page. Charlie delights in making gardening information simple, easy, fun and accessible to everyone. He's the author of 6 books, has three radio shows in New England and a TV show. He leads Garden Tours around the world and consults with organizations and companies about gardening programs. See more about him at Gardening With Charlie.