Growing Sweet Potatoes

 

Norman Kilmer

Sweet potatoes are a very nutritious crop that is easy to grow. They can also be made many different ways to eat and if you like pumpkin pie; you will love sweet potato pie. Personally I like them any way you want to fix them. Boil them until soft, remove the skins, mash them flat, and add a nice helping of butter and some salt. Now there is a meal fit for a king and I am not a king. My wife usually boils more them we eat in a single meal. The rest she removes the skins and puts them in the refrigerator for the next meal. Then they are sliced and fried. Now that’s a meal in it’s self.

Each spring, we sell somewhere around 12,000 - 15,000 slips through our store. And we could sell a lot more if we had the place and the time to start them. They are not hard to grow and we are currently charging $4.00 to $6.00 per dozen slips. So growing sweet potatoes is a business that most people can get into and make some money. They are not that hard to grow.

Starting You Own Slips

Starting sweet potato slips is not that hard but you do need to ask yourself a few questions first:

  1. How many slips do you need?
  2. Are you just needing slips for yourself or are you wanting to grow for others?
  3. Do you have a greenhouse? Or maybe you are thinking of building one soon. A greenhouse is not a must if you are growing for only yourself. However, if you are planning in growing for others, it is almost a must have item.

Growing for Yourself

You have two choices on how you can start your own slips. First of all, you will need a sweet potato. If there is a local sweet potato grower in your area, you most likely will be able to buy a few potatoes from them. If there is not a local grower in the area, just go to your local grocery store. Try to pick out nice looking tubers without any deep cuts or blemishes on them. You may not know what variety they are, but you will have a sweet potato.

If you really want to grow a particular variety of sweet potatoes, you will need to buy slips from a reputable company. Order your slips in from the company you choose and grow them. Save the tubers for seed stock for next year. It will put you behind one year, but it will be worth the wait. Storing tubers will be discussed later in the article.

Starting Slips for Your Home Garden

You will need a quart fruit jar or a empty salad dressing jar will also work. Just make sure your sweet potato tubers fits into the jar opening and each tuber should be at least half way down the inside of the jar. Take 3 or 4 tooth picks and stick them into the sides of the tuber around the top of jar. The tooth picks keep the sweet potato tuber from slipping all the way into the jar. Fill the jar close to the top with water, then place the jar in a sunny location in the house. If you place it on a window sill, make sure it does not get below 50°F at anytime.

After 2-4 weeks, the sweet potato tuber should start to form leaves on the top or side of potato. Let these grow until they are about 6-8” long then remove them from potato. Place these young slips that you just removed from the tuber into another jar filled with water. Leave them in this jar until you are ready to plant your slips outdoors. By placing them in the water, they will grow roots and you have started your own slips! If you leave the sweet potato tuber in the first jar, after removing the slips, it will grow more slips until you remove it from the jar.

Starting Slips for a Larger Grower

This method is for the larger grower or the home gardener that needs to start a 100 or more slips and it requires a greenhouse. We begin sweet potato slip production in our greenhouse in mid to late March. It is very important that you keep your greenhouse temperature at 75-80°F at all times. If it is colder than this, it will take a lot longer to start your slips. In fact, the tubers may rot before starting to grow.

Make wooden boxes that are 24” wide by 40” long and 5 1/2” deep. On the bottom of these boxes, nail a piece of 1/4” plywood. The plywood will only last about 2 years will then need to be replaced. First we put in a 1” layer of Berger BM7 35% 1/4” bark soil mix but any other soil brand will also work. Lay in the sweet potatoes side by side and do not let them touch one another. Fill the rest of the box with soil and add water. Make sure the soil is very wet and do not let it dry out. Keep the soil on the damp to wet side at all times and make sure the thermostat is set at 75-80°F.

In 2-4 weeks you should start to see the sweet potato plants emerge past the soil line. Let them grow until they are 5-6” tall. Then take a sharp paring knife and cut the plants off at about 1” below soil surface. These are your sweet potato slips and at this point they should have roots on them. If you can not plant them right away or are planning on selling slips, you will need to plant them in some soil. You can continue to cut slips off these tubers as long as you keep soil damp to wet. The tubers will continue to grow new slips until you either quit watering them or destroy the bed.

To sell your sweet potatoes retail, we put them in a 4 1/2” square pot and place a little soil in bottom of pot. Put 12-14 sweet potato slips together and place them in the pot. Then fill the rest of the pot with soil. After filling pot with soil and sweet potato slips, soak it until water is running out of the bottom of pot. The first day or so after potting the sweet potato slips, they tend to wilt a little but if you keep them damp to wet, they with snap out of it. You can keep them in a pot for about 14 days. After that they will root together.

Large amounts of sweet potato slips can also be planted in a 9 x 6 mum pot or larger. This is one way of keeping them until you have enough to plant or fill your sweet potato slip order. If you need to ship them to your customer, bundle the slips together with a rubber band. Place them in a paper bag with some peat moss in the bottom and around the roots. Dampen peat moss to keep the roots from drying out.

Growing Sweet Potato Tubers

Now the fun begins because it is planting time! It is a wise idea to have your soil tested because you need a guide line to follow on soil nutrients. Sweet potatoes require 30 pounds of nitrogen, 75 pounds of phosphorus and 250 pounds of potassium per acre. pH needs to be in the 5.0 to 6.0 range.

After applying the soil amendments, work the soil till until it is loose and fairly fine. Fine, loose soil is needed to make good contact with your sweet potato slips root system. We usually hill our sweet potato rows and it is fairly simple if you have a plastic mulch laying machine. If you do not have a machine you can also make them with most rear tine tillers that have a hilling attachment. In the worst case, shovel works also.

On top of the ridge you will need to add a drip line or a soaker hose would also work. Cover the soil with thin black plastic mulch or if you do not have plastic mulch or do not care for it, newspapers will also work. Just make sure that have several layers of newspaper. We prefer black plastic mulch as it warms the soil up early and keeps the weed down in the row.

Space plants 12-14” apart by poking a hole right through the plastic mulch into the soil with a 1/2-3/4” diameter wooden dowel rod. Make sure the hole is at least as deep as your roots are on the sweet potato slips. It is a good idea to turn on the water on for the drip lines before starting to transplant to get the soil wet. This way the newly planted slips have lots of water to start off right away. After sweet potato slips have been planted, keep the soil on the wet side for the first week. After that just need to water as needed but do not let the soil get too dry. At this time and through out the growing season, you can add liquid fertilizer through the drip line. This will give you a higher yield of sweet potatoes. For you organic growers, you can use fish emulsion but if you are putting it through a drip line or soaker hose, strain it really well.

Before the fall frost, you need to harvest your sweet potatoes. Sweet potatoes can be dug by a special potato digger that has been designed to dig sweet potatoes. Or the other way is what most of us have to use; a potato fork. Yes, that is right, dig them by hand, the old fashion way. Yes, I know this gives lots of sore muscles, put look at all the exercise you get! Digging sweet potatoes by hand has lots of excitement also. It is just amazing in all the critters you find below the plastic or newspapers. Some crawl (snakes) and some just run (mice). You also learn that mice love to eat the sweet potatoes too. So you will find some damaged ones.

Be careful when you are digging the sweet potatoes because at this point they are quite fragile and will easily break. After digging them let them air dry and do not wash them. Leave the dirt on them unless they are just too muddy. If they are very muddy, just remove it the best you can with a rag or just use you hands. After they have air dried, put them in a box or basket for storage. Store them at 60°F and no colder. Do not turn the sweet potato tubers why they are being stored. Each time they are turned, the sugars and starches move to the bottom side of the tuber.

Norman Kilmer is the owner of Morgan County Seeds. He can be contacted at 573.378.2655 or This email address is being protected from spambots. You need JavaScript enabled to view it. . You can visit his website at MorganCountySeeds.com.

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