Japanese sweet potatoes, also known as satsumaimo, are a delicious and nutritious vegetable to grow. Their creamy texture and sweet, chestnut-like flavor make them excellent for roasting, mashing, or adding to soups and stews Here is a comprehensive guide on how to plant Japanese sweet potatoes so you can enjoy a bountiful harvest
Overview of Planting Japanese Sweet Potatoes
Japanese sweet potatoes require a long growing season of at least 100 frost-free days. They grow best in zones 8-11. In cooler zones, start the slips indoors 4-6 weeks before the last expected frost date.
The ideal soil temperature for planting sweet potato slips is 65-70°F. Plant them 12-18 inches apart in rows spaced 3-4 feet apart. Japanese sweet potatoes grow on trailing vines above ground and will spread several feet around each plant.
It’s important to use disease-free slips from a reputable source. Give them space for the tubers to size up underground. Maintain even soil moisture and fertilize regularly. Cure tubers after harvest to enhance flavor.
Selecting Disease-Free Slips
Sweet potato slips are sprouted shoots from a mature tuber used for propagation. Purchase them from reputable nurseries and garden centers. Do not use slips from a grocery store potato which may carry disease.
Choose slips with 4-6 leaves and a healthy white root system. Avoid any with brown spots or limp foliage. Slips 8-10 inches tall root the easiest when transplanted.
Inspect the slips closely and discard any that show signs of insects, mildew, or other problems. This prevents introducing diseases into your garden.
When to Plant Sweet Potato Slips
Sweet potatoes require warm soil and air temperatures to thrive. Planted too early, the slips will be stunted or killed by frost.
Most zone 8-11 gardeners can directly plant slips outdoors in late spring after all danger of frost when soil temperatures reach 65-70°F.
In cooler climates, start slips indoors 4-6 weeks before your last expected spring frost. Harden off the young plants. Transplant them outside after the soil has warmed thoroughly.
Planting too late in the season reduces yields. Sweet potatoes need 100-140 days of warm weather to fully develop. Check your average first fall frost date when scheduling.
Preparing the Soil for Planting
Sweet potatoes thrive in loamy, fertile soil. Avoid heavy clay or shallow sandy soils which can restrict tuber development. Ideal pH is 5.8-6.2.
One month before planting, mix in several inches of compost or rotted manure. This boosts nutrition and improves drainage. Raised beds also promote drainage for healthier roots.
The soil should be loose enough for the tubers to expand easily underground. Break up compacted areas and remove rocks and debris that could impede growth.
Planting Methods for Sweet Potato Slips
There are two main ways to plant sweet potato slips: in rows or in hills. Both methods work well as long as you give adequate space.
For row planting, dig a trench 6 inches deep. Create rows 3-4 feet apart. Place slips 12-18 inches apart along the rows and cover roots with 2-3 inches of soil.
The hill method involves creating mounded rows about 12 inches tall and 24 inches across with 3-4 feet between rows. Plant 4-5 slips spaced 6 inches apart atop each mound.
Work a balanced organic fertilizer into the soil before planting. Sweet potatoes are not heavy feeders but need nutrients to perform well.
Caring for Plants During the Growing Season
Once planted, sweet potato plants require minimal care besides watering, fertilizing, and preventing weeds. Vines may reach 10 feet long by summer’s end!
Provide 1-2 inches of water per week. Avoid overwatering which causes roots to rot. Use drip irrigation or soaker hoses rather than sprinklers.
Fertilize lightly every 3-4 weeks with a balanced organic formula. Excess nitrogen results in foliage overgrowth rather than large tubers.
Mulch around plants to retain moisture and reduce weeds. Hand pull any weeds and grass to prevent competition. Hill soil over the tuber zone as vines grow.
Determining When to Harvest
Sweet potatoes are ready for harvest about 100-140 days after transplanting depending on the variety. Time from planting to harvest is called the “days to maturity.”
As tubers near maturity, leaves and vines will start to yellow and die back. Avoid disturbing plants during this stage. Harvest promptly once most foliage is gone.
Carefully dig around each plant with a spading fork. Try not to pierce or bruise tubers. Gently lift the potatoes once the roots are loosened.
Small, immature potatoes may need to remain in the ground longer to reach full size. But harvest all tubers before frost kills vines.
Curing and Storing the Sweet Potato Harvest
Curing improves sweet potato storage life and flavor. After harvesting, brush off dirt but do not wash tubers. Cure for 7-10 days at 80-85°F and 85-90% humidity.
Curing hardens skins, seals injuries, and converts starch to sugar. A basement or climate controlled storage room provides ideal curing conditions.
Once cured, store potatoes in a cool, dry place around 55°F for 4-6 months. Check regularly and remove any that are spoiled. Do not store under 45°F or they may suffer chilling injury.
When to Plant the Slips
When the weather in your area stops dropping below 50°F, your slips will be ready to plant. For my Zone 6a, that’s mid- to late-May. In 2020, I planted my sweet potatoes on May 17th. In 2021, I did the same thing on May 15th (though late in May it got down into the 30s, so I had to cover the plants to keep them from freezing).
But don’t go just by the calendar; let nature be your guide. If it’s still snowing after your last frost date, don’t take a chance (look up your last frost date in the U.S.).
If you got them early and have been taking care of them inside, let them spend a few hours outside every day for a week in soft sunlight (like in the morning) before you plant them. This will help them get used to being outside. If you don’t have a safe space for this (e. g. If you plant in a community garden and live in an apartment, put the slips by an open window.
Sweet potatoes are not terribly fussy and are, in fact, robust survivors. But this work is meant to make beautiful, well-shaped sweet potatoes, and getting the soil ready will help you a lot. The potatoes form underground, so the composition of the soil is everything.
You should deeply turn the soil where you’ll plant the slips at least one week before you plant them. This central planting is often called the “crown,” and that’s how I’ll refer to it in this article.
Then, lightly turn the soil in a 10-foot circle in all directions. As the plant grows, the vines will drop roots at their leaf tips to hold it down. And if you’re lucky, the plant will sometimes make another cluster of potatoes from the nodes, so it might not be a waste of time to turn the whole bed deeply.
Amend the soil throughout the bed with compost. Smooth out the top with a rake, water lightly, and let rest.
Clay soil isn’t good for growing potatoes because it’s not flexible enough to let the potatoes grow on their own. Yes, it is possible, but you will need to add a lot of compost to the crown area to make the soil lighter.
Another type of soil that isn’t good for growing potatoes is one that is very loose and peaty. It’s important for potatoes to have some resistance from the soil so they don’t get too long and skinny or misshapen in a way that makes them hard to cook.
The ideal soil is light and “fluffy”, but holds together well when damp and squeezed. The area should also be well-draining, as sweet potatoes like to be damp, but not drenched. Do the hole test: dig a hole 12″ deep and fill it halfway with water. The water should drain away in the soil at a fairly fast clip. Standing water indicates that the bed needs to be turned more deeply and amended with compost.
How Much Space is Needed to Grow Sweet Potatoes?
I won’t mince words here: you’ll want a big space!
While the sweet potato clusters themselves don’t take up much space—you can even grow them in a big burlap bag or container—they need the food that the plant’s vines produce, which comes from the leaves. And those vines grow incredibly long.
So, actual in-the-ground space needed by the potatoes: small’ish. Actual spread space needed for the vines: large.
I grow all of my sweet potatoes in a 10-foot x 10-foot plot. It’s too small of a plot, but everything works out in the end. When the vines reach the fenced-in edges, I start to direct them to form a circle around the plot’s edges.
You can grow other plants in the same area. Just make sure they are tall enough so their leaves are above the sweet potato vines’ leaves. Though, remember that by the end of the season, the area will be thick with vines and leaves, making it hard to get to. In that case, you could plant something like bell peppers along the plot’s edge. That way, you can easily get to the peppers without walking on the sweet potato vines.
Last year, I grew honeynut squash in the sweet potato bed, and even though there were vines e. v. e. r. y. w. h. e. r. e, it all worked out rather well, and both harvests were quite abundant.
How To Grow Japanese Sweet Potatoes (Satsuma-Imo) | Doctor of the Future 007
FAQ
Can I plant sweet potato directly in soil?
Which way do you plant a sweet potato?
When to plant Japanese purple sweet potatoes?
Do sweet potato plants need to climb?
How do you weed a Japanese sweet potato plant?
To maintain a weed-free area around Japanese sweet potato plants, hand-weeding is required when you first plant the slips. After about two weeks, add an inch of mulch. Add more mulch 1 inch at a time each week for about one month as the vines grow, making the total mulch depth 3 to 4 inches. This will help prevent weeds from growing around the plants.
How do you plant sweet potatoes?
Plan 3 feet between mounds so there is enough space for vines to run. Plant the slips on a warm, overcast day when the soil temperature has reached 60°F (15°C). Break off the lower leaves, leaving only the top ones. Set the slips deep enough to cover the roots and the stem up to the leaves. Sweet potatoes will form on the nodes.
How do you grow Japanese sweet potatoes?
To grow Japanese sweet potatoes, prepare the soil by loosening it to a depth of 12 inches and water it well before planting. Japanese sweet potatoes need at least six hours of direct sunlight per day. During the growing season, water the soil regularly. This will help the roots of the Japanese sweet potato slips to establish themselves more easily.
Can you plant a Japanese sweet potato from the grocery store?
Yes, you can plant Japanese sweet potatoes from the grocery store. Choose a smooth-skinned variety, as those with rough skin are more likely to be treated with sprout inhibitors. Cut the tuber into pieces, making sure that each piece has at least two eyes or buds.