We’ve passed through the month for “magical” sweet potato development, so it’s time to think about digging your nutritious treasures. By “magical,” I mean some references say sweet potatoes double their yield every two weeks in the month of September. Be very careful in digging, for their skin is quite tender now and cutting into them or scuffing them can shorten or destroy their usefulness.
Sweet potatoes are very nutritious, rich in vitamins and minerals while low on the glycemic index scale, and easy to grow in our soil. I think the reason many of us have considered them a Southern crop is that curing them involves high temperatures and humidity. Boise’s sweet potato king (Thomas F. Edwards, founder of Edwards Greenhouse in the early 1930s) used his former (first) house as a curing location, with coal or wood-burning stoves for heat and probably pots of water on the stoves providing humidity, according to his granddaughter, Garnette Edwards.
Is curing necessary? Some folks think it’s only necessary to heal wounds inflicted during digging, and others think it’s not necessary if you plan to use the sweets within a couple of months. Some experts say curing sweet potatoes enhances eating quality, heals wounds and “sets the skin” that will affect the storage longevity of the tuber. It’s nigh impossible for us in this climate to cure sweet potatoes at 85 degrees Fahrenheit and relative humidity of 85 to 90 percent for even one day, much less the three to five days after harvest, especially since we usually harvest in October’s cool weather.
Some folks say we can cure these potatoes by placing them in an oven, with a thermometer inside and putting a light bulb on a cord inside the oven, almost closing the door. Check the temperature after an hour and then either open the door a little more or change the bulb wattage to get to 90 degrees. A pan of water on the floor of the oven is expected to provide humidity, but that may depend on the presence of a pilot light heating the water. Modern ranges don’t have pilot lights. This technique may be worth a try, however.
However, consuming sweet potatoes shortly after digging them or winter squash shortly after harvest may be disappointing because it takes some time (at least a few days) for the starch in most of those vegetables to sweeten. Exceptions are delicata, dumpling, spaghetti, acorn, and a few other winter squashes. Sweet potatoes and butternut, large hubbard, and kabocha types of squash develop the best taste after resting for several days after harvest.
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Close inspection shows that damage to bean leaves in my garden was caused by spider mites, not thrips. Hot dry weather contributed to conditions favoring spider mites in both varieties of beans at the edges of my raised beds, so they were not closed and humidified by other plants or weeds. I do have a lot of lady beetles in the garden, and they’re very good about consuming spider mites (about nine per hour), but the population was more than they could handle or they wanted a change of diet and went after aphids instead. Prior to the hot weather, aphids were controlled by wasps, but later in the season they lose their hunger for aphids.
The spider mite damage shows as tiny black flecks, webbing across the undersides of the leaves, and a yellow stippling where the mites have consumed the green chlorophyll. Since they principally occupy the undersides of leaves, spraying is difficult because the spray must actually contact the mites’ bodies, rather than having a residual effect. Soap sprays or plain water are effective, IF you can get either sprayed there.
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On Sept. 23 or 24 or both nights, frost blackened many of the sweet potato leaves in my garden. Storms were coming in from the south, and my garden is open in that direction, save for two beds that have heavy pole beans at the south end. They apparently shielded both of the western beds from cold air. Forecast lows were for the 40s, and since adjacent pepper and tomato plants were not damaged by frost, I was interested to learn the temperature at which sweet potato vines were damaged. A website on past weather history indicates the low temperatures those nights was 36 degrees. Basil in one of those bean-protected beds was not frosted, and that usually blackens at 38 degrees Fahrenheit, so the bean barrier worked for that crop.
Send garden questions to firstname.lastname@example.org or Gardening, The Statesman, P.O. Box 40, Boise, ID 83707.