Growing Sweet Potatoes – by Mark Govan, host of “Florida Gardening” heard on 970WFLA
Daytime temperatures in the upper eighties and low nineties severely limit choices we have to grow in the garden. One of my favorite plants, the sweet potato, is easy to grow and a great choice for summer gardens. Sweet potatoes have a very long planting season with some people starting theirs in early March, while others will wait for the heat during the summer in June. Luckily, sweet potatoes will grow in just about any soil as long as you work in a little compost or peat. This week I will explain to you how to grow the “slips” you will use to start your garden and/or where you can purchase them. I will also tell you how to prepare your soil to give you a great crop of sweet potatoes. You need to begin planting now, so let’s get started.
Growing your own starter slips is easy. Select a good-sized sweet potato and stand it on end in a glass of water, pointy side up. Sometimes, you may need to use toothpicks to hold it from falling over. In a few short weeks, your potato will start growing short vines. When these growths or slips as we call them are at least six inches long, break them off at the base and put them into a small cup or vase. Add a small amount of water to cover the bottom of the slips. In about a week, they will start producing roots. When the roots look pretty thick, separate the slips and plant them into the garden by following my steps on preparing your garden below.
Those of you that do not want to wait to grow your own slips, which could take three to four weeks, may want to stop by your local garden center and see if they have any available. Some garden centers order slips from their suppliers for public consumption. These centers may want you to pre-pay for these slips because they do not last long on the shelf. Once the slips are delivered to the store, they will call you to pick them up. This way, you can put them directly into the garden. A few stores even carry some of the hard to find cultivars of sweet potatoes so check around. By pre-ordering your slips for delivery on a certain date; you will have plenty of time to prepare your garden for planting.
Sweet potatoes, like loose, well-drained soil with copious amounts of compost to produce pounds of sweet potatoes for the table. If you have not amended the bed that you are going to plant your sweet potatoes in, then you will need to do that now. Because our soils are very sandy and contain little organic matter, you will need to add enough compost and peat to make a rich soil mixture that will easily hold its shape when compressed in your hand. For most people, this means you will have to add at least a couple twenty-five- pound bags of Black Kow and two or three twenty-five pound bags of a good potting soil or peat for a standard five-by-five foot garden.
Compost can be used in place of peat above. Do not forget to add three to four pounds of a good quality 8-10-10 granular fertilizer and two to four cups of minor essential elements before mixing the soil. Your five-by-five garden will accept two rows of slips spaced a foot between plants and three feet between the rows. You should be able to plant ten to twelve slips. Continue to fertilize your plants with small amounts of fertilizer every three to four weeks. You can also spray the foliage of your plants with a liquid fertilizer like Peter’s or Miracle Grow mixed at the one-half strength rate every ten days.
Sweet potatoes, like it hot so do not be alarmed when temperatures rise. Remember, the tuber that forms the sweet potato is below ground so you should not have to worry about your plants drying out as long as you water them regularly. A two-inch layer of cypress mulch will help keep your plants from drying out. Most sweet potatoes are slow to put on their foliage as most of their nutrients go to root production first. Remember, sweet potatoes are members of the morning glory family and although the plants are not widely known for their flowering characteristics, they will sprawl so try to keep them in check. Weed the garden every two weeks and pull them by hand so you do not injure the soft skin of the developing tubers (new sweet potatoes). Weed grasses steal nutrients from your growing tubers so remove them as they develop. Some people will add straw in place of cypress mulch around the rooted slips to help keep weeds away.
Now that your plants are growing, keep checking on them and inspect for insects and disease. If you see something that does not look right, take a sample to the cooperative extension office in the county you live for advice on how to control the problem. In about three to four months, your potatoes will begin to mature. Unlike potato vines, which wither and die signaling a ripening crop, sweet potato vines continue to grow. Check your sweet potatoes for proper size by digging a few up by hand. Be careful while lifting your potatoes because any injury to the sweet potato can cause them to rot very quickly. If your sweet potatoes are of proper size, based on the cultivar you planted, then it is time to harvest.
Try to dig your sweet potatoes on an overcast day or in the early morning to lessen the chance of injury to your new tubers. Harvesting always damages some of the potatoes because the tools used always seem to slice into the new tubers before they have had a chance to cure. The less pressure needed to unearth the tubers reduces the chance of crop injury. Be sure to dig at least two feet away from your plants in all directions so you do not miss any of the wandering tubers. After you have unearthed all the tubers, allow them to dry on the ground, out of the sun for a few hours.
Next, you should cure your harvest by storing your unwashed sweet potatoes in a cool dark place for at least seven days. This process toughens the sweet potato and seals out disease organisms. After curing you can wash your sweet potato crop and place in dry storage for months to come. Your five by five gardens can produce a bigger harvest than you may think so get started now to enjoy the fruits of your labor. There is no better feeling than enjoying fresh vegetables produced from your own garden.
I have also been asked about the tubers which grow from the ornamental species of sweet potatoes. Many people wonder if they are poisonous or not. The short answer is no. You can eat them. I had a very large patch of the purple, chartreuse green, and even the variegated types of ornamental sweet potatoes. They all produce large tubers and can be eaten, but their taste is very bland. You need extra butter and brown sugar to make them palatable. Most ornamental sweet potatoes are grown for their attractive foliage, not the taste of the tuber. Sweet potatoes, used for the table are grown for their sugar content and taste.
June is a great time to start your sweet potato gardens. Starting your plants from slips grown in the home can save you money and a trip to the local garden center. Prepare your garden soil with plenty of compost and make sure you add some fertilizer to the mix. Once planted, you will need to monitor your plants for insects and water your plants regularly. A layer of mulch will help to keep your plants from drying out in the summer heat. Allow your plants to spread out and in about three months, you should be able to start checking on how large of a crop you will have. Be careful digging out your sweet potatoes and be sure to cure them. Good luck in the garden and remember, without plants we would not be here!