ROCK RAPIDS, Iowa — Last May I embarked on a home gardening experiment. I had read that sweet potatoes provide the most nutrient dense “bang for the buck” and they can be successfully grown in our northern climate. After exploring nutritional advantages and planning for the best possible growing conditions in my experimental sweet potato season, it was time to implement my plan.
We lucked out this spring when Mother Nature provided exceptionally warm weather. The short growing season in Northwest Iowa usually requires taking extra steps to raise the soil temperature to at least 70 degrees before planting. Not this year. By the first week in June the soil was already warm enough to plant the sweet potato slips I had purchased. And our exceptionally hot summer was a bonus for growing sweet potatoes.
Fast forward to early October. Predictions for early frost caused me some anxiety since I had not yet dug up my crop. Harvesting sweet potatoes before soil temperatures drop below 50 degrees is essential. In less than a day in cold soil they will experience ‘chilling injury’ and begin to deteriorate. So I literally rushed out to dig up whatever my June planting had produced. Surprise! I could have, would have and should have harvested them earlier. Some of the potatoes were at least 12 inches long and some as large as small pumpkins.
Sensitivity to environmental conditions extends to harvesting as well. Sweet potatoes might appear firm and indestructible but they are easily bruised. Since those bruises quickly turn to rot, we are advised to dig them up gently. Whoops! My soil was so wet and dense digging ‘gently’ was difficult. I dug them up as carefully as possible. Whew! They are out of the ground. Now what?
My pre-planting research also turned up another surprise. Sweet potatoes are not good to eat until they are properly cured. They must be kept in a warm (85 degrees F) and humid (relative humidity 90%) location for 5 to 10 days after harvesting to convert starches to sugar, heal wounds and grow a thicker skin for storage. Whoops again! October temperatures around here are usually nowhere near 85 degrees. I ended up with a bathtub full of sweet potatoes and a plan to keep the bathroom door closed with the furnace cranked up to 85 degrees for the next 10 days.
Lessons learned: Make sure your soil is light and mounded for good drainage and easier harvesting. Don’t wait until the leaves turn color before digging them up; the leaves on my sweet potatoes were still green when I finally harvested them. Plan ahead to provide a warm, humid location for curing.
At this time my first sweet potato harvest is still curing. Guess I will have to wait a little longer to see if growing my own sweet potatoes to make Thanksgiving sweet potato pie was worth the effort. Perhaps next year I’ll grow pumpkins…
— Pat Kosters, Iowa Master Gardener
For more news from Iowa, click here.