How to Plant (& Harvest) Sweet Potatoes – Complete Guide

Is your vegetable garden suitable for planting sweet potatoes? Probably! Sweet potatoes grow quite well without a lot of attention; they are drought-resistant, love the heat, and have few diseases or pests. The most important thing to keep in mind when learning how to grow sweet potatoes is that they require warm soil to grow.

They can still be grown in northern regions, as long as you have 100 or more days in the growing season, and the soil is adequately warmed. Additionally, sweet potatoes need to be cured, or they will not taste their best!

Planting Sweet Potatoes - Where to Start

As mentioned, the most important requirement for growing sweet potatoes is warm soil. Sweet potatoes do not tolerate frost, will not grow at temperatures below 16°C/60°F, but will do best in soil temperatures from 80°C/27°F to 37°C/100°F. An average soil temperature of 24°C/75°C is recommended. Pick a location in the garden that is sunny and as weed-free as possible.

Soil Requirements for Growing Sweet Potatoes

Sweet potatoes do best in well-drained, sandy, and fertile soil, although they will grow in less fertile locations. If grown in clay, the potatoes may grow longer and narrower(or misshapen). Soil that has pH of 5.5 to 6.5 (slightly acidic) is most favorable.

Warming the Soil

If you are vegetable gardening in the Northern United States or Canada you will need to consider warming your soil before planting sweet potatoes. The best way to do this is to prepare a planting bed that is covered with clear plastic. There has been some debate about using clear plastic vs black plastic, but the general consensus is that clear plastic is preferred. Clear plastic warms the soil better than black plastic; the latter will absorb and deflect much of the heat.

How to Build Warm Beds

Building the appropriate bed for sweet potatoes can be started 2-3 weeks before planting. Planting can begin one ambiant temperatures are consistently above 16°C/60°F. Weed the vegetable garden before preparing the bed.

1. Create a raised bed of dirt that is at least 18 inches wide and 8 inches tall. Level the top as best as possible so that air pockets will not be created. The raised nature of the bed will allow quicker warming. 

2. Lay a ~4-foot wide length of clear plastic over-top the length of the row. This will leave 12 inches of plastic on each side of your row.

3 . Cover one of these 12-inch sides with dirt (for the length of the row) and pack down so that the plastic is held. 

4 . Pull the plastic tight from the opposite side, and bury the 12-inch edge that is still exposed. Ensure that you keep the plastic as tight as possible with no air space between the dirt and plastic. This will help keep weeds down and heat in.

How and When to Plant Sweet Potatoes

Sweet potatoes are planted from "slips". Slips are live cuttings from sprouted vines from sweet potato tubers. Slips can be purchased from a local nursery or delivered by mail. You can also grow your own. As previously mentioned, planting sweet potatoes can be started once the soil temperature is consistently above 16°C/60°F. In Northern areas, this may be late May or early June.

Here are the steps for planting sweet potatoes:

  1. Cut ~8-inch slits every 18-24 inches down the middle of your prepared rows.

  2. Create a 12-inch diameter shallow depression at each 8-inch slit.

  3. Plant a slip in each slit. Plant the slip so that 2-4 leaves are still visible above ground. For the first few weeks the slip will establish roots and it will appear that nothing is happening above ground.

  4. Fill the depression around the plant with sand so that the slit is sealed. Rainfall will now be directed to the base of the plant.

Harvesting Sweet Potatoes

After planting sweet potatoes, the vines will begin to grow strongly during mid-summer. In late-summer the tubers will begin to swell and should be left as late as possible. The tubers can be harvested any time they have reached a desirable size. This usually occurs 3-4 months after planting slips.

Once temperatures begin to dip below 16°C/60°F the plants will stop producing. Once frost has turned the vines black the tubers should be dug up immediately. Lower temperatures can injure the tubers leading to rot after storage. A garden fork works great for gently prying up the sweet potatoes.

Once you have dug up the tubers, wash them gently under the garden hose and allow to dry. Washing keeps dried soil from brushing off when handling inside. Now it is time to cure your sweet potatoes!

Curing Sweet Potatoes

Sweet potatoes need to be cured for 1-2 weeks in order to taste their best. During curing, the starches within the tuber will gradually convert to sugar. Once harvested, washed, and dried, the tubers should be placed in a room with a temperature of 85-90°F/29-32°C with a humidity of approximately 85%. The curing process also help heal any nicks or injuries from harvesting, which will help the tubers store better.

Storing Sweet Potatoes

Storing potatoes is fairly simple. Place then gently in boxes in an area that maintains a temperature of 13-16°C/55-60°F. The ideal humidity is around 75-80%. Be careful, sweet potatoes bruise easily, which will lead to rot. Properly stored sweet potatoes will last up to a year! The taste will only improve with storage.

We now hope you try planting sweet potatoes in your vegetable garden!

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