Written by Dale Richardson - Updated: June 23, 2023
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Sweet potatoes can be an exciting growing adventure for new and experienced gardeners alike. Even though they need a long season of warm weather, don't let this discourage you from trying them even if you have a short cold season. Follow this guide to grow sweet potatoes in your own self-sufficient garden.
Prepare the garden bed by loosening the soil and mixing in compost. Sweet potatoes are typically grown from slips. Plant the slips in the garden or a pot after all danger of frost has passed. Keep the plants well-watered throughout the whole season. Sweet potatoes require 90 to 150 warm days to mature. Harvest before the first fall frost. Ideally, you want to wait until the plant starts to yellow, or until the tubers are 8cm (3inches) in diameter. Harvest carefully to avoid damageing or bruising the vegetable.
Sweet potatoes are a tropical, fast-growing vine that thrives in the sun and warmth. In warm countries, they are a prolific, creeping vine that makes an excellent addition to a permaculture garden. In most gardens, sweet potatoes are an annual root crop that can be grown successfully if you provide a long and warm growing environment. Here is how to successfully grow sweet potatoes in your self-sufficient garden.
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There are two ways to grow sweet potatoes: from slips or from cuttings.
The most common way to grow sweet potatoes is from slips. Slips can be purchased from many seed companies or you can produce your own.
What is a sweet potato slip?
If you place a sweet potato in water or in a thin layer of soil, it will soon sprout and send up little shoots. These sprouts can be broken off the sweet potato and this is a sweet potato slip. This slip will soon send roots out of the bottom and will grow into a sweet potato plant. A sweet potato slip can be planted directly into the soil, or it can be placed in a glass of water first to develop roots and get a head start on the growing season.
If you order slips or buy them from a garden centre, they will often be wilted, dry and off colour. This is perfectly fine, and they can be planted right away. If you need to delay their planting, wrap the root end of the slip in a damp paper towel (make sure not to cover the leaves or the stem), and keep them at room temperature out of the sun in a vertical position.
Image by Moss
If you plan on starting your own slips from a sweet potato bought at a grocery store, be aware that many sweet potatoes are chemically treated so they do not sprout on the shelf. While a conventional sweet potato may sprout, it is best to buy an organic sweet potato as these most likely have not been treated.
In most gardens, sweet potatoes are an annual crop. Sweet potatoes are stored over winter and a new crop is grown each spring from the slips.
In warm countries, where sweet potato vines grow all year long, new plants can be grown from cuttings .
To grow your sweet potatoes from cuttings, cut a piece of the vine about 30cm (1ft) long. Remove all the leaves from the cutting except the leaves right at the tip. Plant the vine in the ground, leaving the tip and leaves above the ground. Each node on the cutting will produce roots underground, and this cutting will quickly establish itself as a producing sweet potato plant.
Whether you have purchased your slips or grown them yourself, you plant them the same way. Choose a warm and sunny spot to grow your sweet potatoes.
Purple Sweet Potatoesgrowing purple sweet potatoes
Sweet potatoes are a root crop, so how you prepare the soil will greatly improve the plant's health and yield. Sweet potatoes prefer sandy or loam soils, but they can be grown well in any soil type. Whichever soil you have, they will grow best if the soil is nice and loose to about 30cm (12inches) deep, but 20cm to 25cm (8-10inches) is usually sufficient. You can read more about how deep the soil should be for sweet potatoes in this article here . Sweet potatoes like moisture but they well quickly rot if the soil is too wet or if they are in standing water. Raised beds also create a very excellent growing environment for sweet potatoes.
Mix in a good amount of compost into your bed prior to planting. As a root crop, sweet potatoes greatly benefit from phosphorous, which aids in healthy root production and growth. adding compost or animal manure to your soil before planting is the best way to provide phosphorus to your sweet potatoes. Green manuring also adds phosphorus and humus to your soil while suppressing weeds between your vines. You can also water them with compost tea throughout the season to provide phosphorous as the tubers grow.
Image by UnconventionalEmma
Do not give your sweet potatoes too much nitrogen, whether as a fertilizer or in compost form. Chicken and horse manure, for example, are high in nitrogen and might not be the best to supplement your sweet potato patch. Too much nitrogen will produce a vibrant, healthy plant with very few tubers.
Sweet potato plants do not handle any frost, so plant the slips in the garden after all chance of frost has passed. Sweet potatoes need a soil temperature of at least 16°C (60°F). Plant the slips about 10cm (4inches) deep, or up to the first set of leaves, with 30cm to 45cm between each slip. Keep them well watered until they are fully established.
Unlike potatoes, you do not have to hill sweet potatoes while they are growing. Sweet potatoes are relatively easy keepers and only require basic care during the growing season. Since they are tropical, they do best when provided with regular water but even as mature plants they will rot quickly in a wet environment.
The one thing sweet potatoes need is heat and plenty of it. Sweet potatoes need around 90 to 120 days that are consistently warm and frost-free. The more heat they get, the better they will grow, and the larger your harvest.
As we discussed earlier, a cutting will produce roots from its nodes if the nodes are underground. In the same way, a sweet potato vine may send out roots from the vine as it trails along the ground. These roots, however, can take nutrients away from the plant and lower your yield. It is a good idea to periodically check your vines throughout the summer and lift them to keep roots from developing. Alternatively, you can put in trellises for the vines to grow up. This has the added advantage that it allows sunlight to warm the base of the plant and help it grow.
Avoid watering your sweet potatoes the week before you plan to harvest. This can make them easier to harvest and cleaner when they come up.
Harvest your sweet potatoes before the first frost. Sweet potatoes will not tolerate frost. The tubers underneath will quickly rot if the vines die. The best indicator that the sweet potatoes are ready to harvest is when the plants start to yellow and die back. The tubers should be ideally 8cm (3inches) in diameter when harvested.
To harvest sweet potatoes, remove the plant from the roots. Carefully dig the soil around the base of the plant with a garden fork. Don't dig too close to the base or you risk spearing the tubers (they will still be edible but they will be unfit for storage). Sift through the soil with your hands and pull out the fruits of your labour. Handle the fresh dug sweet potatoes carefully as they bruise easily
How many sweet potatoes you get from one plant greatly depends on how your growing season was. One plant will yield anywhere from 4 to 10 sweet potatoes per plant. If you live in a Northern climate, you will be leaning towards to former.
Sweet potatoes can be cured and stored for several months so you can enjoy them all winter long.
If you live in a northern area, you can still grow sweet potatoes but you have to provide a little extra care to give them a long enough warm season. Growing them in raised beds might be enough to raise the soil temperature sufficiently, or you might want to grow them under black plastic for extra heat. Of course, you can use a polytunnel or greenhouse for season extension.
If there is no way you can reasonable keep them warm enough in the garden, consider growing them in pots. You can start the pots indoors in the early spring, put them out in the sun through the summer, and bring them in on cold, frosty fall nights.
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