I have had good/great success growing regular potatoes in a planter, but limited success with sweet potatoes. My sweet potato leaves always look GREAT, but not that many sweet potatoes. As with my regular potatoes, I make the soil somewhat acidic, not too much nitrogen, and also added epsom salt. I have tried to maximize phosphorus and potassium, but maybe not enough?? I have wood ashes - maybe that would help? The sweet potatoes I do get often have black lines/splits/cracks in them and look rather horrendous. Not sure what causes that - a bug, fungus, what? I'd appreciate any tips you might have for growing them in a planter. I live in Ohio, zone 6.

My daughter grows sweet potatoes in containers. She uses regular potting soil in black pots. The black pots are for heat as sweet potatoes are tropicals. She does not fertilize - there's fertilizer in the potting soil. Her sweet potatoes are always awesome! Maybe you are over-doing all the nutrients?

PS: She uses moisture control soil because its hard to keep the 'taters damp in the desert.

Sweet potatoes mature in 90 to 170 days and that's a long time for being in a container. I would say that may be the reason you are having problems. In order for Sweet Potatoes to thrive they need a sandy loam like soil with a pH of about 5.8 and 6.2.

Try regular potting soil like Daisy recommends because the pH is right. Plant your slips in the bottom of the container, and as they grow upward add new soil and keep adding until you get a pot of sweet potatoes. Good Luck

oneeyeluke said:Sweet potatoes mature in 90 to 170 days and that's a long time for being in a container.

She uses really big containers, probably 15 gallons or more and they are pretty full of sweet potatoes by fall.

I'm not sure planting your slip at the bottom of the pot is a good idea for sweet potatoes. The potatoes are growing as roots, not off the stem like a regular potato. I can ask my daughter how deep she plants.

@DaisyI - Let me know what your daughter says about the depth.
@oneeyeluke I am thinking I may need to lower the pH a bit more then.

She plants them about 6 inches down. She says when she planted them deeper, they only grew tops and roots, no potatoes. But thinks that if the growing season was longer, eventually 'taters would have grown on the stem. She also uses water walls all summer to keep the plants hotter. When she didn't use water walls, she didn't have potatoes.

One year she used plastic tents, the temperature inside was 140F and the plants did not wilt but it was hard to water and the wind kept tipping them over. Her assessment of your problem is not hot enough. Her girlfriend, from Singapore, grows them - the lowest ever temps are in the 80's.

Maybe clear plastic on the soil? (clear plastic works better than black plastic - its the greenhouse effect )

That is interesting. I could try a tent. Does she have any idea about why the potatoes I do get often have black "cuts" in them?

so I did some Googling and it said that to much water at the end of the growing period can cause them to split - I bet that is what I am doing. It said watering should cease three to four weeks before harvest. I know I did not do that.

The splits are due to watering at the wrong time. The black lines are mold growing in the splits.

I do think that is true - we have had periods of drought, followed by heavy rain. I think I need to make sure it stays watered during the drought so they don't then split when it rains. I am learning a lot!!

I had ornamental sweet potatos one year, in pots by the front door, one grew a huge tuber , the other none!. One pot might have more sun than the other.
Where you are I would try to start the plants early as possible.
Are you growing your own slip, or buying them?
When I grew them in ground, they make a big cluster of tubers right under the main stem., it even sort of pushed up out of the soil by end of summer. But I am not sure you should bury them deep to begin with. I have read, do NOT let the rest of the vines root, or you may get more but smaller tubers.

sallyg said:Where you are I would try to start the plants early as possible.
Are you growing your own slip, or buying them?
When I grew them in ground, they make a big cluster of tubers right under the main stem., it even sort of pushed up out of the soil by end of summer. But I am not sure you should bury them deep to begin with. I have read, do NOT let the rest of the vines root, or you may get more but smaller tubers.

I grew my own slip and have already started it indoors, under a window. It has started leafing out already. I am going to put a plastic tent over it to help keep it warmer as suggested. I also put some wood ash on it yesterday, along with soil acidifier and some more epsom salts.

cwhitt said:
I also put some wood ash on it yesterday, along with soil acidifier and some more epsom salts.

Why?

Wood ash is naturally high in potassium. It also contains phosphorous as well as a bunch of micronutrients including manganese, iron, zinc and calcium. Only problem with wood ash though, is it raises pH - so that is why I added the soil acidifier. Will test the pH later after some of the ashes soak in - might need to add some more acidifier.

https://www.growveg.com/guides...
The article does say "Don't apply it to areas used to grow potatoes, as alkaline soil encourages potato scab.", but I did use it on my red potatoes last summer, with soil acidifier, and it did fine. But I will keep testing the soil to make sure the pH is low enough. The article also said "You'd need to add lots of wood ash to make your soil too alkaline for most crops." so I think as long as I check the pH, I should be OK - I hope. Also added some biochar. I hear that green beans like wood ash also, so I have started putting some of that in my green bean bed. THis will be my first summer to test that.

But you are growing in a container. That's a whole different ball game.

Be aware that "white'" potatoes are a whole nother plant than SWEET potatoes. I think potato scab is a disease on "white" potatoes.

DaisyI said:But you are growing in a container. That's a whole different ball game.

I don't understand what you mean.

Containers are closed systems - there's not a lot of places for extra nutrients and water to go. Everything (nutrient-wise) you add should be cut to 1/4 to 1/2 strength. If you are using potting soil, it has a 6 month supply of fertilizer built in already - longer than most growing seasons.