There are few foods as nutritious, versatile, and delicious as sweet potatoes. They’re loaded with beta-carotene, vitamins A and C, pack lots of fiber and can be prepared in dozens of ways. As a bonus, sweet potatoes are really easy to grow in your garden and suffer from few pest and disease problems.
Sweet potatoes are not related to potatoes, and they are grown very differently. Whereas sweet potatoes are a long season crop that grows on trailing vines, potatoes are grown early in the season and do best in cooler temperatures. Sweet potatoes thrive in the long, hot summers of the south, but there are varieties that will grow just fine in the north, even in Canada.
Sweet potatoes are not grown from seed potatoes, but from “slips”, which are shoots that sprout from the storage roots. Make sure that you order your slips from a reputable nursery to avoid any disease complications.
Please don’t say “Yam” when you mean sweet potato, because they belong to two unrelated plant families (please inform your grocer of this). Sweet potatoes (Ipomea batatas) are related to the morning glory family of plants. Yams (Dioscorea family) are a completely different species.
Read more on Yams from Penn State University
How to plant sweet potatoes
1. Plant sweet potato slips in a garden bed in full sun after your last frost date has passed.
Sweet Potatoes won’t withstand a sudden plunge in temperature, much less a freeze. In fact, check your soil with a soil thermometer and make sure the soil temperature is 55 – 60 degrees. If it’s cooler than that, the slips won’t do much in the way of growing.
2. Plant the slips on hills or ridges about eight inches tall, so the roots never sit in water.
The soil should be on the loamy side with plenty of finished compost added to it so that it drains well – sweet potato roots despise a waterlogged soil.
3. Bury all but the upper leaves of the slips, which means you’ll plant them 3-4 inches deep.
4. Space the plants 12-18 inches apart straight down the center of your raised garden bed.
If your raised bed is wider than 36 inches, plant in two staggered rows. If you’re not using raised beds, plant the slips in rows 3-4 feet apart. Sweet potatoes produce a massive amount of foliage – if you plant them any closer, they won’t have room to flourish come mid-season, and the sweet potato tuber will not develop properly. The more space they have, the larger and sweeter the tubers will be.
5. After planting, mulch the hills with straw and add an organic source of phosphorous such as bone meal to encourage root and tuber growth.
Important: Don’t add a high nitrogen fertilizer, as it will stimulate lots of foliage growth and little in the way of sweet potatoes.
Sweet potatoes are pretty thrifty water-wise. They only need about 1 inch a week, including what falls from the sky. And once the vines have covered the bed, the soil is well insulated, retaining plenty of moisture. They’re virtually maintenance-free at this point until harvest unless your growing season is very dry.
When to harvest and cure sweet potatoes
Most varieties of sweet potatoes are ready for harvest 90-110 days after planting the slips. You’ll know it’s time when the leaves begin to turn yellow. You can harvest small potatoes as you want them before this date, but use them immediately, as they won’t store well. Be forewarned that sweet potatoes which haven’t been “cured” are not very sweet.
How to cure sweet potatoes
The key to long-term storage is curing the sweet potatoes correctly. When the leaves turn yellow, cut the vines and allow the sweet potatoes to remain in the soil for 2-3 days before digging them up. Dig them on a warm, dry day and let them dry on top of the soil for 2-3 hours. Shake off the excess soil from the tubers, but don’t rub off any fine soil clinging to the sweet potatoes. The skin is very tender just after harvest and wiping, scraping, or washing the sweet potato may wound the skin, which will cause rot in storage. Keep ’em dry and dirty.
Ideally, for perfect curing, the sweet potatoes should first be stored in a warm room at 85 degrees for 2 weeks, and then placed in a cool location (55 degrees). But of course, few of us have an advanced setup like that. My drying and curing method is to spread the potatoes out in baskets lined with newspaper for about 10 days until they’re completely dry. I store them in old school wood potato storage bins I found at an auction, and they do quite well in my garage. I place (not drop or throw, as they’ll bruise easily) the sweet potatoes in the bins and they keep well into the winter months. It’s not a perfect storage solution, but it works just fine. I inspect the bins every few weeks for any tubers which may be turning soft and I use those right away or toss them out. You can also use wooden crates if you don’t have official potato bins.
Recommended Sweet Potato Varieties For Your Garden
(according to the University of Illinois Extension)
- Beauregard (100 days to harvest, light purple skin, dark orange flesh, extremely high yielder from Louisiana State University)
- Bush Porto Rico (110 days, compact vines, copper skin, orange flesh, heavy yield)
- Centennial (100 days; orange skin, flesh; good keeper; resistant to internal cork, wilt)
- Georgia Jet (100 days, red skin, orange flesh, somewhat cold tolerant)
- Jewell (100 days, orange flesh, good yield, excellent keeper)
- Sumor (ivory to very light yellow flesh, may be substituted for Irish potatoes in very warm regions)
- Vardaman (110 days, golden skin, orange flesh, compact bush type, young foliage purple)