Valley Bounty: Sweet Potatoes

For years, Ryan Karb struggled to grow sweet potatoes. “I asked myself, ‘Am I not weeding them enough? Am I not watering them enough?” he explained.

Frustrated with year after year of lackluster sweet potato harvests, he turned to the farming community for advice. Karb learned that for sweet potatoes, quality can vary significantly between the suppliers of slips, what farmers use to start sweet potatoes.

“Getting weeds under control, managing fertility well, and irrigating was all really important. Without that base I wouldn’t have had better years,” he said. “I had all that in place and then switched suppliers. It was like magic. I just started getting four times the yields.”

Ryan Karb runs a ten-acre farm in Amherst called Many Hands Farm Corps. Many Hands offers community supported agriculture (CSA) shares year-round, including a winter share that runs from December through March. For Karb, storage crops including carrots, potatoes, onions, and garlic are the cornerstone of that winter CSA share. These days, his favorite storage crop is without a doubt sweet potatoes.

On Many Hands, the preparation for planting sweet potatoes begins in the late summer and early fall. That’s when Karb plants a cover crop of oats and tillage radishes to prepare the soil.

“The tillage radishes will grow a couple of feet into the soil, get up to three inches thick, then die off in the winter,” Karb said. “When you come back in the spring, they will have shrunk. They leave these big holes in the soil.”

The tillage radishes loosen the soil so Karb doesn’t need to do any mechanical tilling in the spring. Instead, he takes out a small cultivating tractor outfitted with a disk implement.

“I’ll make hills about a foot high,” he explained. With the hills made, the field is ready to receive the sweet potato slips as soon as they arrive in the mail, typically in late May.

Sweet potato slips are vine cuttings, cultivated by leaving sweet potato roots in sand or soil until they sprout. Unlike most crops, which farmers start from seed, sweet potatoes are started by planting these slips directly into the soil.

Because the slips are living plants, it’s important to plant them quickly once they arrive. But that lack of flexibility can leave Karb in a bind if cold weather is predicted to sweep in right around the time the slips are delivered.

“They’ll often die in the first two or three days if they’re not planted in the right conditions,” Karb said.
Cold weather becomes a threat to sweet potatoes once again during harvest time, which typically comes in the last weeks of September.

“The longer you leave them in the ground, the bigger they get,” Karb explained. “So every week that they stay in the ground a little longer, you’re adding ounces, maybe even a pound, per foot in yields.”

But leaving the sweet potatoes in the ground is a gamble because if a hard frost hits before the harvest, it can cause significant damage to the crop.

When Karb does decide to harvest, the process is no easy task. “It’s definitely the dirtiest I get of all the crops,” he said, “because the vines and leaves exude this sugary sap that dries up and soil gets mixed in it. It’s like having glue on your hands, it’s really hard to get off.”

But despite all the challenges of growing sweet potatoes, Karb loves the crop.

“It’s a couple weeks of worrying when they’re planted, two days of suffering through the harvest in the fall, but then months of enjoyment,” he said.

“If I don’t know what I’m making for dinner, I’ll dice up a sweet potato and roast it then add it to just about anything,” Karb explained. Some of his favorites dishes to add sweet potatoes to include tacos, spinach and sweet potato curry, and roasted sweet potatoes on soba noodles with a tahini dressing.

Even if you didn’t sign up for a winter CSA share this year, there’s plenty of local sweet potatoes available right now. Visit to find a local farm stand near you.

Noah Baustin is the Communications Coordinator at CISA (Community Involved in Sustaining Agriculture)