How and Why to Grow Sweet Potatoes and Protect Them From Rodents

This article was originally published in the  November 2024 edition of What's On.

In this post I'll share why sweet potatoes are a super crop to grow at home, some ideas for overcoming challenges with growing them (including protecting them from bandicoots and rats), and why it's a good idea to eat the leaves as well as the tubers. 

The sweet potato plant (Ipomoea batatas) is a climbing and ground covering vine. It can be very easy to grow, once you overcome a few challenges. 

One challenge is that the tubers can be hard to find if you allow the vines to sprawl out across the ground. Another is that rats (particularly a native rat that burrows up from underneath where we live in North Queensland, Australia) and bandicoots love sweet potatoes as much as people do. 

But please don't give up! Sweet potato plants are really, really worth the effort to try to grow yourself and this article I'll share some tips that might help.

But first, why are sweet potato plants so worthwhile? The answer in a nutshell is "nutrition plus calories."

Sweet potatoes - lots of nutrition AND calories from the same growing space

Did you know that you can eat the tips and leaves of the sweet potato vine as well as the tubers? 

In the image above you can see sweet potato greens (on the right) and okinawah spinach. The sweet potato greens will take a lot more cooking than the okinawah spinach will.

So long as you eat the leaves as well as the tubers, sweet potato plants can yield significant levels of Vitamins A, B, C, and K, as well as Thiamine, Niacin, Zinc, Folic Acid, Calcium, Riboflavin, and Iron.

Sweet potato plants are also mineral rich, providing significant magnesium, copper, manganese, phosphorus, and potassium. The tubers (especially the orange-fleshed varieties) are a good source of beta-carotene for healthy vision, and tryptophan, an essential amino acid that supports healthy sleep. They also have a low glycemic index rating, meaning they're easy on our blood sugar balance.

Improved artery and heart health, healthier eyesight, reduced inflammation, reduced risk of diabetes, cancer, and neuro-degenerative diseases, stronger bones, and healthier skin are among the possible outcomes of regularly including sweet potato tubers and greens in your meals.

Sweet potato greens taste bitter, so add a dash of vinegar to the cooked greens and serve them alongside the sweet tuber to encourage your people to eat up and get the health benefits of the bitter taste.

Sweet potato roots and greens combined give you a calorie and nutrient dense food from one growing space, which is unusual -- usually you get either calories or lots of nutrients, and you have to combine different plants to cover these two bases.

How to protect your sweet potato crop AND make it easy to find the tubers

Sweet potato greens and tubers can be produced in containers in a smaller space than you might think, and container growing has a few advantages for the home gardener:

• Sweet potato vines grow roots where-ever the leaf nodes come in contact with the soil, and some of these roots will swell into tubers. So a sprawling, ground covering vine will produce lots of tubers, but they'll be relatively small and hard to find. Containing them in tubs and training the vines up a trellis means less tubers, but it also means more sunlight-harvesting leaf surface (up on the trellis) per tuber. So besides being impossible to loose track of, your tubers will be bigger, sooner.
• By setting your containers on concrete or a hard surface, you can foil the native rats that burrow up from beneath¹. You can also use containers that are too tall for a bandicoot to climb into (and we place our containers near the house, where the presence of our dog further discourages bandicoots and rats).
• Lastly, sweet potatoes are relatively pest free but what pests they do have are often soil-borne; growing in containers enables you to control the soil they grow in much more closely.

The containers in the picture above are set on concrete to prevent native rats from burrowing up from underneath. But they need a trellis to enable the vines to climb up into the sunlight, and to prevent the ones on the ground from rooting at the leaf nodes and forming tubers that will be too small. 

Growing conditions

Sweet potatoes like well-drained, loose soil, slightly acidic.  Potting mix is fine. Loose soil is important for your tubers to be able to expand as they develop, and for easy harvesting.

For a crop of big tubers, you'll need plenty of sunlight. If open sunny spaces are limited, arrange for  the vines on the trellis to reach up into the sunlight. For greens only, a shadier spot will be fine; the leaves will be bigger and softer if grown in partial shade.

Sweet potatoes need about 2 to 4 months of warm weather, reasonable sunshine, and consistent moisture to produce decent sized tubers. In tropical areas, you may be able to grow them year round. 

If you're after greens only, you can use a small container. If you also want tubers, you'll need space for 5 to 10 large tubers per plant. Provide a trellis and train the vines up it to be sure the plant has plenty of leaf surface area to harvest the sunlight it needs to produce big, fat tubers.

Starting off

Sweet potato plants can be started from "slips," which develop from sprouts on a sweet potato tuber. Or, you can take cuttings (runners) from an existing plant and use those. 

Start slips throughout spring and early summer. Partially submerge a sweet potato in water or soil and wait for it to sprout. When the sprouts are about 15 cm in length and have little roots of their own, twist or snip each one off, bringing its roots with it. Trim off the leaves on the bottom third or so and plant it carefully up to its arm pits in soil.

If you're taking cuttings from an existing plant, choose runners that are robust and growing strongly (avoid older, woody ones or thin, flimsy ones). Cut them into pencil-length cuttings, remove all the leaves, and plant them upright. Submerge the bottom one third to one half of the cutting in the soil. Or you can use longer cuttings, leave a leaf or two on them, and lay them down with only their leaves exposed. They will root at each leaf node. 

The pic above shows a trimmed sweet potato runner ready to plant. Zoom in tosee the roots already starting at one of the leaf nodes.

In the pic below, the same runner has just been planted. It will need to be protected with thick mulch and kept moist until well established.

Keep your baby sweet potato plants consistently moist and out of direct sunlight until they're big and strong.

Harvest

Harvest leaves and tips once the stems are at least 30 cm or so long, a month or two after planting. If you’re using leaves from a crop intended for root harvest, limit harvesting to a couple of  times a month. If you only want greens you can harvest more often, and in frost free areas or with indoor containers you can harvest greens year round.

Harvesting tubers: Search for hard mounds indicating swollen roots just under the soil surface. Either tip the container out or burrow into it with your hands and pull out your treasures. After harvesting, lay your sweet potatoes in the sun for a few hours to dry, so the the skins can start to "cure" -- to harden against injury, mold, etc. Continue curing in a warm dry place for a few more days and then store in a cool, dark, dry place. Do not refrigerate.

Sources 

Nutritional information about sweet potato tuber and greens from"Sweet potato leaves for family nutrition: Overview of research"and "Sweet Potato Nutrition Facts and Health Benefits."

Tips on propagating sweet potatoes from cuttings are from Gardening Australia.