Growing sweet potatoes as houseplants & garden crops

by Lala

Given the opportunity, I always pick sweet potato fries over regular french fries. I can’t resist them roasted or mashed as well. Sweet potatoes are not only tasty, but they also grow as beautiful vines that make for interesting, easy going houseplants or ornamentals outdoors.

Although they are both tuberous vegetables, regular potatoes and sweet potatoes are from different families. Regular potatoes are from the Solanaceae (aka Nightshade) group, along with chillies, tomatoes, and eggplants, while sweet potatoes are from the Convolvulaceae (Bindweed) group, with morning glories. In fact sweet potatoes bloom with flowers that are very similar to morning glories. The leaves of regular potatoes are toxic if ingested, while the leaves of sweet potatoes can be safely eaten & are commonly found in vegetable markets in tropical countries. I remember seeing them at Marché de Flacq in Mauritius.

Growing sweet potatoes

The process of growing sweet potatoes couldn’t be easier. If you have any sweet potatoes from the supermarket that are past their prime & starting to sprout, you can do this. It is best to start with sweet potatoes that are at room temperature. I know some people keep their vegetables in the fridge. Leave the tubers out for a day before attempting to sprout them. This process is also best started indoors or in warm weather outdoors. The sweet potatoes will go dormant in cold weather (more on that later).

Place the sweet potato in a clear container where it will be partially submerged in water. Making sure at least half the sweet potato is submerged has worked well in my experience. I found that narrow-necked, glass containers that are used to force bulbs work really well for this. However, any container in which the top of the tuber can be above water, will do. You can use an ordinary drinking glass too.

Place the sweet potato in a bright spot, like a kitchen windowsill. Change the water every two or three days. Using a clear container will help you to monitor the water quality. If the water is murky, change it immediately.

Within a few days or a week, the “eyes” or small nubs will have developed longer stems and the beginnings of leaves.

Warm weather means faster, lush growth. Soon the tuber will grow green leaves which can be different shapes and colours, depending on the variety of sweet potatoes.

Plant different colours and varieties of grocery store sweet potatoes, to get different leaf shapes. Garden centres also have specially-selected, ornamental sweet potato plants with leaves that are dark purple, variegated or even yellow.

At this point the plant has long vines called slips, and a good amount of long, fine roots. This means it is well established. Some people keep them like this indefinitely, still regularly changing the water. I like to change their growing environment at this stage. The leaves can also be harvested for cooking at this point.

When the tubers have this many leaves on the slips, I either plant the whole tuber with slips in a pot with soil (or moss); or twist the slips off from the tuber and plant the slips alone in water to keep indoors.

The slips can also be planted in the garden soil outside if I want to grow more sweet potatoes for eating. It takes about 3 to 4 months from planting the slips, until the sweet potatoes are ready to harvest. Thus, it is best to start your slips in spring do that you’ll have enough warm weather to develop the tubers. You harvest the sweet potatoes when the leaves above ground start to turn yellow. The sweet potatoes can be left in the ground until autumn, before the first frost or ground freeze. At this point the plant is done growing and all the energy is stored in the tubers. In nature, that is it’s dormancy phase. For us gardeners and urban farmers, it is harvest time.

The leaves are so beautiful. It’s important to twist the slips off, not cut them off. Twisting off keeps some of the roots.
These are slips I kept going in water. They can get very long.
This is a sweet potato that I started off like the previous one, and later planted in a pot with moss, as is.
The sweet potato planted in a concrete pot, with sphagnum moss and a stone for a “bonsai” effect.

This one grew well in the late summer and autumn of 2019.

By winter the leaves had mostly fallen off and the plant reverted to the small stem stumps as seen above. I kept it outdoors all winter in a mini greenhouse. At some point I thought it had died, but I didn’t get around to throwing it away, since I didn’t need to use the pot for anything else. By spring, the plant started to come out of dormancy and grow new leaves. It really took off after the first few weeks of spring rain & warm weather in Shanghai.

This is the plant this week. I keep it permanently outdoors.

Growing sweet potatoes like this seems to be a popular hobby of plant lovers in Shanghai. I’ve seen them grown this way at restaurants and as below, outside a Japanese tailor’s shop in Lujiazui.

Sweet potatoes are even used in the city’s vast and seasonal urban horticulture installations, including on traffic islands and road medians.

Have fun growing your sweet potatoes. This is an easy, “quick win” project to get into with the kids, if you are stuck at home because of the COVID19 Lockdowns.

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