Sweet potato is a vegetable that’s eaten as a staple food on almost every continent. But have you ever wondered how sweet potatoes grow? Do they grow on vines or underground, like potatoes?
The part of the sweet potato that we eat grows under the ground. It’s the swollen root of the sweet potato plant. Their depth and harvest time vary with the cultivar, soil and growing conditions. Above the ground, sweet potato plants have a vining growth.
Sweet potato plants, Ipomoea batatas, belong to the Convolvulaceae family, so they are close relatives of flowering morning glories. Sweet potato stems and leaves are edible, but the tastiest part of the plant is what grows underground. Let’s now discuss how sweet potatoes grow and explain how easy it’s to grow them in the garden.
Do Sweet Potatoes Grow Underground Or On A Vine?
Sweet potato plants grow above and below ground.
Above the soil surface, they are vining plants with heart-shaped foliage. Underground, they have thick, starchy roots.
Sweet potatoes grow underground and are considered root vegetables, not fruits that grow on a vine.
How Far Underground Do Sweet Potatoes Grow?
The storage roots form underground around the plant; they are not confined to one fixed depth.
Plant healthy slips at the depth recommended by your regional extension guide, leaving the growing tip and leaves above the soil.
The swollen roots of the sweet potato plant can grow up to a foot from the main stem and above-ground foliage.
Fine roots and the swollen storage roots you harvest are different parts of the root system.
Are Sweet Potatoes Roots Or Tubers?
Regular white potatoes are called root vegetables, but the starchy spuds that we eat aren’t actually true roots.
Potatoes are technically tubers or modified stems.
So, are sweet potatoes tubers, too, or are they actual roots?
Sweet potatoes are classified as true roots. They aren’t a tuber or modified rhizome.
Sweet potatoes have what’s called an adventitious root.
The swollen roots are an evolutionary adaptation to store water and sugars below ground to survive through times of drought.
Sweet potatoes are tropical plants that are adapted to warm climates.
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Can You Grow Sweet Potatoes In Water?
Yes, you can grow sweet potatoes in water, without any soil.
People usually do this to grow sweet potato vines indoors ornamentally.
Their beautiful heart-shaped leaves look a bit like pothos.
You can even grow a sweet potato from the grocery store in water. Just place it pointy-end-down into a jar of water.
About a third of the sweet potato should be under the water.
Place the sweet potato in a warm spot with bright indirect light. Keep the water in the jar topped up.
After about a month, you will start to see little sprouts forming from the top of the sweet potato.
These are called slips. You will also see roots growing into the water.
You can use the slips to grow many new sweet potato plants by planting them in the garden for food.
You can also just plant them in pots to enjoy the sweet potato vine itself.
How To Grow Healthy Sweet Potatoes?
Sweet potatoes need a warm growing season and well-drained soil. Even established plants need adequate moisture for a good crop.
It’s no wonder that they are a staple food around the globe.
Start with healthy sweet potato slips from a reliable supplier or sprout suitable stored roots. Sweet potatoes produce shoots, not the potato eyes found on stem tubers.
You can also buy sweet potato slips from garden centers in spring and early summer.
Plant A Sweet Potato Into The Ground
You can just bury a sweet potato directly in the ground, and it will grow into a vine and eventually produce more sweet potatoes underground.
But there are better ways to get more sweet potato plants per spud.
Grow Sweet Potatoes From Slips
Sprout the sweet potatoes in water jars and wait for the slips to grow.
When they have developed leaves, gently twist the slips loose from the sweet potato.
Place the slips in a shallow dish with their lower halves submerged in water.
True roots should start growing in a few days.
When the slips’ roots have grown an inch long, plant them into small pots.
You should use a loose potting soil with good drainage.
Grow the slips indoors on a sunny windowsill. Soon they will become lush little vines.
Plant Sweet Potatoes In The Garden
In spring, you can plant your little sweet potato vines outside into the ground.
They aren’t frost-hardy, so you must wait until a few weeks after the last frost date to plant them.
Plant the sweet potatoes in a position that gets full sun.
Use the planting depth and spacing in your regional extension guide, keeping the leaves and growing tip above the soil.
Prepare well-drained garden soil according to a soil test and local guidance. Do not assume adding sand to any soil will improve drainage.
It takes a while for the sweet potato vines to bush up and cover the soil.
Keep the bare soil around the sweet potato plants weeded so that they don’t have to compete for water or soil nutrients.
Water the sweet potatoes once a week, maybe twice a week if the weather is very hot.
Your sweet potatoes should take off in no time.
Grow Sweet Potatoes In A Pot
Without a big enough garden, you can still grow a sweet potato plant in a large pot and grow your own sweet potatoes!
Find a pot that is around 18 inches deep. Sweet potatoes need at least 2 cubic feet of soil to grow in.
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How To Harvest Sweet Potatoes?
Sweet potatoes need to be harvested before the first frost of the fall.
You can harvest and eat the sweet potatoes when they are still small.
However, you should wait until they are mature if you want the largest possible crop.
Expected harvest time varies with the cultivar and growing conditions.
Use the cultivar’s expected harvest period and check root size. Flowering is not required and is not a dependable harvest signal.
Many cultivars need roughly 95 to 120 days after transplanting, but local climate and cultivar can change that timing.
Use a garden fork to loosen the soil around the sweet potato vines carefully.
Start digging well away from the crown and work carefully below the roots to avoid cutting them; do not assume every root is in the top six inches.
