Sweet Potato Planting Guide
You’re thinking of purchasing, or have purchased, the fantastic Sweet Potato plant slips we sell on a Pre-Order basis in bundles of 25 in our store and online. (click link to go to our Sweet Potato Ordering page!)
The slips we order for you usually come to us in April for pickup, so here’s what to do, and what you need to know, to get ready in the meantime.
Guide for Growing a Great Sweet Potato Crop from Plant Slips
Sweet Potatoes are really not fussy. They will flourish in some of the worst conditions and still give you good tubers to eat at the end of the season. Here’s what you can do to help them along and have beautiful sweet potatoes to show for it.
The Soil
Hard clay or tightly-packed limestone soils (like our infamous Florida sugar sand) will need to be loosened down to about 10 inches. Amend with Shell’s Naturals 3-3-3 Organic Fertilizer and/or your compost, so that there are nutrients readily available and the soil will hold at least some water.
How To Plant
Make a 10″ (the sweet potato guide from the grower says 8-12″ high) mounded row, and if you have multiple rows, make them about 3′ apart. You will want to make the row(s) in a place that gets full sun. When the danger of frost is over (it should be OK in April here in Florida when these come in), poke a 6″ hole in the top of the mound every 10-18″. Evenly spaced plants will produce the most consistent sized sweet potatoes. Place the slip in the hole roots first, and pour a little water on the roots in the hole. Secure firmly in the soil, being careful not to cover the bud/leaves completely. Water well when planting is done.
You will want to plant on a sunny afternoon after the sun is no longer directly overhead with very little wind.
We have seen recommendations for mulching heavily in some references, and not at all in others. Since you’ve made relatively wide mounds, mulching would be difficult in our opinion, however, you could do so if you choose. I have seen people put straw and leaves in between the rows (there is 3′ of space there!) to deter weed growth and make it easier to keep weeds away from the area. The vines themselves will choke out most weeds and grasses once they have grown into their thick mats of intertwined vines and leaves.
Delayed Planting
If you have to delay planting your slips for any reason, you must remove the slips from the carton, remove the rubber band, waxed paper and moss from the roots. Setting the root ends on wet sawdust, moss, wet burlap, or something like it, will keep them healthy for several days longer, just don’t wet the stems or leaves. According to the guide from the grower, “plants will succeed even if they are yellow, slimy, and have an odor that is almost unbearable”. That’s a mighty endorsement of their hardiness!
Vine Care
Occasionally go through and lift vines away from the ground to keep them from rooting at the joints and making small tubers there, as this will take away from the main activity at the base of the main plant. Otherwise, avoid touching the vines if possible, as any little nick or scar can easily introduce disease, being so close to the ground. You can also trellis the vines, though you will have to GENTLY guide and secure them, as they do not grab like cucumber and bean vines do.
Either way, the vines will reward you with pretty flowers, as sweet potatoes are a member of the morning glory family. The flowers do not need to be pollinated to make sweet potatoes, they are strictly ornamental, but you will find bees and other helpful insects feeding off of them.
Watering
Sweet potatoes are better with drier soil. If it has not rained, give them 1″ of water once a week. Too much water will cause the tubers to rot. Once the vines have grown into their thick mats, the vines will act like a natural mulch to keep water from evaporating as fast.
Fertilizing
We recommend working Shell’s Organic 3-3-3 into the soil along with any composted organic material you prefer (worm castings, mushroom compost, your own kitchen scrap compost, untreated raked up leaves and grass clippings, etc) before you plant. You can add more 3-3-3 during the growing season until you see the leaves start to yellow late in the growing cycle, this means that your first harvest is imminent!
Harvesting and Expected Yield
Sweet potatoes mature over a long period, 90-170 days is typical. That means you can dig up one or two plants at a time as you consume them, and leave the others to continue to mature over that approximately 3 month maturity period. You can begin to harvest as soon as the vines begin to turn yellow, and it should be done on a sunny day when the soil is dry. The longer you leave them in the ground, the more flavor and vitamins they accumulate.
A 10′ row of sweet potato plants will yield about 8-10 pounds of sweet potatoes on average. Since they are planted about 12″ apart, a 10′ row is about 10 plants, give or take if you chose to plant them farther apart, so about a pound of potatoes per plant is a good yield. As you’re harvesting, remember that the tubers can be over a foot away from the base of the plant, so be careful when you’re searching in the soil for the tubers. Any nicks in the tuber can cause spoilage (though, for the most part, they are pretty hardy!). Try to get all of them harvested before any danger of the first frost, because after a freeze they will rot quickly.
Since these were grown in a mounded row, you can hand-pull the soil away from the plants to unearth the tubers underneath quite easily, and after you get to the level of the ground between the rows, use a shovel or pitchfork to carefully dig for the rest that are growing deeper under ground.
Once harvested, you will want to remove the vines from the sweet potato. If the vines are disease-free you can put them in your compost bin (if they are diseased you should burn them). Once dry, gently brush the dirt off of the tubers, but do not wash them. Place them in a warm, well-ventilated, shaded area, not touching one another, to air cure for 8-10 days to dry out. This builds flavor and also will force the tuber to heal any damage from harvesting and grow a thicker skin around themselves for storage. Cardboard is my surface of choice for this process – a flattened shipping box or a produce box will do.
Storage
Sweet potatoes are ideally stored in a cool, dark space, about 55 degrees and 75% humidity. In northern states, root cellars were common for this. Here in Florida, my suggestion is a small refrigerator that you can set the exact temperature digitally, and have an open container of water inside to provide some evaporative humidity (which will be removed by the cooling process of the refrigerator). Or, if that’s not an option, keep in a dark place that is well ventilated, wrapped in newspaper, and check on it once a week to see if it is sprouting or rotting. Use them as soon as you can.
As an alternative, many health experts tell us to eat food when it is in season in our particular area, right? So, when it is harvested and cured, eat it right away! Or prepare it and freeze it, like you do when you get a mountain of squash and zucchini all at the same time. Then you won’t have to worry about storage.
Sweet Potato Pests
Sweet Potato Weevils – they have “evil” in their name – are the most destructive pests. Adults burrow into stems and tubers to lay their eggs and the larvae eat their way down the stems and into the tubers, while the adults decimate the foliage and vines. They are very hard to kill because they burrow, and if you get them, it’s probably best to pull the crop and burn infested plants, then wait 4 years to try any kind of potatoes again in that space (crop rotation is always a good idea in a garden anyway).
Other pests include black rot and stem rot, both fungal diseases caused by insect damage, wind, and carelessness with the vines. If the plants have this the harvest will be poor. Black rot will look like dark spots on the tuber, usually kind of mushy, and deep into the flesh. Black rot can affect select tubers from the same plant, so if you find one tuber with black rot, make sure you carefully separate them from the healthy tubers as you harvest so you don’t spread the disease. Discard the affected tubers (or stems, from stem rot) by burning, or place them in the trash (don’t compost, the fungus may linger and infect other plants).
Sweet Potato Weevil
Sweet Potato Weevil Larvae
Black Rot, compared to a healthy tuber
Scurf is not pretty, but it is not harmful. It looks like dark spots on the tuber, but it doesn’t affect the eating quality, it’s more on the surface only as compared to black rot.
We are here answer questions on growing, caring for, and taking care of pests in your garden. When you pick up your slips from us in April please ask for the growing guide from the grower, it has lots of good information as well. And remember, if you run into disease or pest issues, we have regular and organic solutions to all the garden problems you might have and are happy to help. Please let us know what we can do for you!