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Growing your own Sweetpotatoes; all you need is Time

Q. Dear Mike: I'm interested in growing sweetpotatoes in my garden. I tried it a few years back, but they looked awful. I ordered slips from a place I found online in Texas, and they arrived looking sad. Even after planting them in a raised bed and watering well, the leaves were all wilted and/or yellow and brown. Do you know where I might find local sweetpotato slips (preferably organic)? I'd really like to grow my own because of the pesticides used on commercial crops—and because it's hard to find supermarket sweetpotatoes that aren't moldy looking and gross. Thanks!
    ---Jennifer in Havertown
A. Ha! You remind me of one of my favorite lines from my (now sadly out of print) coffee table book, "Kitchen Garden A to Z". Every entry had a brief "how to buy" tip, and the one on sweetpotatoes said: "Good luck. The best sweetpotato doesn't look all that different from the worst one. Avoid visible rot." In other words, while they are one of the healthiest things you can grow, these crazy relatives of morning glories will never win any beauty contests.

Now, before you all write in to try and correct my spelling, the correct and official way to represent these tubers in type, according to the USDA, is one word: Sweetpotatoes; this is to try and help get across that they are not any kind of potato. (They're also not any kind of 'yam'; that's a misnomer that goes back almost a hundred years.)

Now: sweet potato slips—the little plants from which those mighty tubers grow—are perishable and fragile, so you might want to consider starting your own. Take a fully-grown sweetpotato—from a reliable mail order source if possible; if not, from the supermarket should be fine—and bury the bottom three quarters in a box of moist sand. Keep the sand moist without letting it get sopping wet.

The slips—green shoots with exposed roots—will soon sprout out of the skin. When all danger of frost has passed, gently pull the slips from the mother plant and plant the roots in rich, loose soil where the plants will have lots of room to spread. The vines will soon cover the ground (for quite some distance; they are space hogs) and the tubers will develop slowly below. Water normally; don't drown the poor things.

Your desire to begin with organic stock is admirable, and I see organic sweetpotatoes for sale at natural food markets throughout the Philadelphia area. But don't sweat it if you can only find so-called "conventional" tubers as planting time approaches. Just use no chemicals in your garden; that's the important part.

Q. Mike: I planted sweetpotatoes for the first time this year (from purchased slips). But when I thought it was time to harvest there were no full-size potatoes, just a few 'bumps' that were smaller than fingerlings. Did I harvest too soon?
    ---Arlene in West Chester PA
A. Yes. sweet potatoes take a long time to mature and should be harvested AFTER the first frost, especially in the North and other short-season climes. (A little chill won't harm the tubers, and it concentrates the sugars and improves the flavor, as with carrots.) AND the weather in Pennsylvania was very uncooperative for sweetpotatoes and other long-season crops this year: Record wetness, record coolness and way too few sunny days—none of which improves your sweetpotato odds.

In general, these nutritious roots are easier to grow down South and in other regions with long seasons. Three months of warm weather is pretty much the bare minimum to get good-sized tubers; four months for big, full-sized ones. In the North, this means having your slips ready to go as soon as the weather cooperates and leaving the roots in the ground until the very end of the season. Many home gardeners will also warm up the soil with clear plastic a few weeks in advance. Some will leave that plastic on for the first month or so to retain heat. In the extreme North, they'll use black plastic and leave it on all season.

In short, warm up the soil, get the slips out on time, and pray for sun and warm weather. Or live down South.

Q. When I pulled up my ornamental sweetpotato vines, I discovered a healthy crop of what I assumed were sweetpotatoes: big fat purple ones from the purple vines and some white tubers from the chartreuse vines. Can I eat them? Are they poisonous? Tasteless? I asked a friend who has a degree in horticulture and she suggested I ask you.
    ---Margaret in Harvey Cedars, NJ
A. Ha—I'm honored! Luckily, I spoke to a couple of extension agents about this subject a few years back and they all felt pretty confident that the incredibly colored tubers from ornamental vines are safe to eat, but probably won't have much flavor. "They ARE true sweetpotatoes", I was assured, "but these plants have been bred to have dramatic foliage, not good taste or a high sugar content in the tubers."

The final word on this topic, however, belongs to a listener who has eaten the things and lived to tell this tale:

"I grow ornamental sweetpotato vines, and this year decided to harvest and sample the tubers. I cleaned them really well, peeled them (the peel is very thin), then steamed and pureed them with milk, butter, cumin, salt and pepper. I suffered no adverse affects, but must report that they ARE a bit bland—so be sure and spice them up if you try it.
    ---Maryanne Sage
PS. Yes, 'Sage' is my last name. And I garden for a living and love it!"

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