please share ideas for growing BIG sweet potatoes, several pounds per plant

We've grown them for years on three different pieces of land.
I've never done soil tests nor really added any amendments aimed at growing a great crop.
The oldest orange potatoes I clone are going on 30 years now and the purples at least five.
https://permies.com/t/17569/perennial-vegetables/sweet-potato-propagation-harvest
I've read where they can play out eventually but I was able to grow a twenty pound cluster (and also an 8#  and a 10#)from the oldest strain just a few years ago....and a few huge purples last year but not all of them and have not been able to duplicate that success.....some years are okay to good but not outstanding.
pictures below are of the twenty pound plant!



Here's what I've read recently that I see lacking in my methods ...

...choosing the potatoes for slips from plants producing at least four nice potatoes.

...feeding the soil, especially potassium.

...watering often enough they don't wilt.

...not letting the vines root along their length

...mulching, (we only do sometimes)

This years crop of purples were average size and only around a pound per plant except for three plants that produced the cluster of at least four good ones...they were still just around two pounds total.  I have an occasional single 3# potato from them though so I know they are capable.

This years orange, old variety, cut leaf produced a couple plants with one or two nice size but mostly small clusters of roots.

Some in tubs, some in holes I added sand to and some in clay that dried to a brick but still had similar size potatoes.

I suspect lack of nutrients rather than soil tilth.
The 20# plant was a left over slip, planted late in unworked ground in the front yard .. it also had a pile of pine logs near by from a recent tree removed from that yard...no amendments and we almost forgot about it until the rest of the garden crop was dug.

I hadn't thought about discouraging rooting along the vines' travel along the ground. Might have to give that a go this season...always looking for the cool ways to tweak the system. I didn't cover the surface with biochar last year before planting because I couldn't bear to have that much exposed soil. The plants established quickly in spite of the lack of extra heating so I will just plant directly into mulch this time as well.

I think allowing rooting along the vines in a longer season works and they will make more potatoes  along there also.  Here, I think it just takes energy away from the main plant.

Here's some photos of information from a book put out by our local extension service for this state...usually good info if we ignore the chemical solutions promoted and they do acknowledge organic growers now😊

As a long time grower of sweet potatoes in several regions, I can vouch for not letting the vines root along their length, unless perhaps you are in so tropical a climate as to have them basically become a perennial groundcover, and even there, finding the largest roots to harvest would still be a challenge.  Raised beds and mulching help with this, but in wet weather roots will grow down through mulch, and then going along the rows and lifting the vines and setting them back down helps, and/or stuffing coarse mulch, bundles of sticks, etc. up under there as well.  
   Not letting the leaves droop from drought is also important.  In fact this is good for just about every kind of vegetable.  When I was growing for high-value organic markets I was taught that if you see foliage droop on anything, even if it recovers overnight, you are losing yield and quality.  Although yes, in a homestead situation resilience is also important, and you will still get a yield in spite of this.  A long drought followed by heavy rain can also make roots split.
    Most important of all, though, is to work toward what I call a "fluffy" soil....this goes for carrots as well.  Neither likes a heavy clay and it will lead to small twisty roots on both.  Sandy soil is ideal, good loam is good too.  If you have clay the answer is finely divided organic matter incorporated in.  I used to make this by running a mower over dry leaves, grass, etc. in the pathways between those beds allocated to these crops, and then dig and/or till this into the beds themselves...up to an inch or two depth of "powder" per year.  A bit of urine helps counteract the nitrogen uptake issue with this kind of organic matter use, but fortunately neither sweets nor carrots like a lot of N anyway.
   

I haven't worried much about maximizing production as I've mostly been focused on breeding them for growing as seeded annuals. I do think that allowing them to root along the vines, especially if they have a trailing habit takes away from a nice harvest of larger roots and instead makes lots of little ones. Worse they are all spread out and hard to find and harvest but you might get by with it if you have a longer season and don't mind digging a crater to find them. I grow them mostly in pots and have selected for bushy, non-trailing vines and a clump of nice roots directly under the primary stem: I think those traits would also be nice to have even if growing in the ground.

I also haven't worried much about specific soil nutrients or anything else that would require me to test for or purchase anything, I just grow them in what I can scrounge up around the place. I do think though that a nice loose soil helps encourage larger roots and keeping them well-watered helps too. One year I saved a bunch of yard clippings and leaves and kept them dry in bags in the shed. In spring I mixed that up with some pretty decent compost and a little plain garden soil. That was the best ever as far as production, I got two to four pounds per 3.5-gallon pot. *If you grow in pots, especially small ones it is important that the drain holes be buried in the ground, so they don't dry out so fast and so feeder roots can exit into the soil below and never move the pots once those roots have established.

I saw a fellow on YouTube that grew them in large Rubbermaid tubs with a very specific soil recipe of purchased potting mixes. He had a fantastic harvest, many pounds per tub. It looked like most of the space in the tub was filled with just sweet potatoes. It was interesting but not something I would do because it violates my buy nothing policy, plus I don't need hundreds of pounds of sweet potatoes as there are only two of us here to eat them.  

Next year though, I am going to revisit the issue of maximizing production and have already stockpiled several large bags of leaves, weeds and grass to fill my pots. As I move to this new phase of my breeding project, I'm setting a goal of averaging three pounds per 3.5-gallon pot.

I know nothing, and I'm a terrible gardener (yield wise, anyway), but if I could only grow one plant for food, it'd be the sweet potato.  They love it here in the desert southwest.  I've had plenty of failures with them (watch the video for proof), but all in all I generally do well growing them.  I went crazy this year and planted about 70'ish slips mostly in containers, and about 20 or so in the ground.  I planted two to three slips per 15 gallon nursery pot (closer to a 5 gallon bucket in size).  I haven't harvested yet since there's still some time left until my first frost.  

The first plant I pulled was from a plastic 10 gallon nursery container?  It's about the same diameter as a 5 gallon bucket, but several inches shorter in height.  I used a mix of old potting mix I save every year, and I mixed in a bunch of my chicken litter/wood chip compost.  I fertilized with some Alaska fish fertilizer a half a dozen times up until about July, and then they just got plain water (very hard, mineralized, chlorinated, city water).   I'm dreaming of 200lbs, but I will be thrilled if I get over 50lbs, lol.  The first plant I pulled got me all excited because it had 8lbs exactly, then I pulled three other GIANT plastic containers, and only 8oz total from all three!!!  I was bummed.  

Every plant in the yard came from three organic Stokes purple sweet potatoes I got at Smith's grocery store in February.  I started propagating them in February, and to my surprise they started forming shoots within days (first time that's happened).  I was up to my ears in slips/shoots and from those three potatoes I got probably over 150 usable shoots.  I gave some to the veterans at the veterans home I work at (super cool to see them growing at work!!!), and a bunch of others to my neighbors.  I started putting them in grow bags and plastic containers in the beginning of March in my greenhouse, then I ran out of room in the greenhouse, and started rooting them is large plastic red cups so I could transplant them to larger containers outside around May.  

I'll upload some pics of what I actually got in a few weeks or so (first frost here).   I can't upload the iphone images from the phone I was using.

Here's a cheesy video of my rambling about it.  I'm not too good at videos.  I did use ai for the thumbnail, and it did a great job!  

edit, let's see if my other pictures will work.

edit again.  I figured out how to convert them.

How do you keep them for next years planting?    Will the tuber survive all winter in the fridge or root cellar?  

This year I got starts from Baker Creek.   https://www.rareseeds.com/.  I would like to keep these genetics and protect them.  

I live in the north and I am thankful to get any sweet potatoes.   I got the hardiest, short season, cool summer tolerant variety I could find and put them in my best soil, in the sunniest, most protected location.   I put them in after the soil had warmed and the harsh winds of winter had passed.
I did not add any nutrient as they were growing but the soil they started in was quite rich from well rotted manures.  

The plants were very healthy looking when they were growing and even tolerated a couple light autumn frosts!
I have not dug them all up yet but I am getting about 10 pounds per plant.  

Hi Samantha,
I don't cure mine, I tried it once and they started to mold.  I just throw them in my room temperature pantry (well I try not to use a heater, so it's probably 60f-70f most of the time during the winter) and they last until spring.  I ate all of last year's so I had to buy new ones this season.   I can start so early (Feb-Mar), and harvest so late (Nov-Dec) mine don't need to stay in storage but a few months or so.  Rarely do they rot, but some will every year.  I just toss them out to the chickens/compost.

Ten pounds per plant is awesome!  If I can get half of that per plant I'll be one happy guy!

Good luck!

Joshua Bertram wrote:Hi Samantha,
I don't cure mine, I tried it once and they started to mold.  I just throw them in my room temperature pantry (well I try not to use a heater, so it's probably 60f-70f most of the time during the winter) and they last until spring.  I ate all of last year's so I had to buy new ones this season.   I can start so early (Feb-Mar), and harvest so late (Nov-Dec) mine don't need to stay in storage but a few months or so.  Rarely do they rot, but some will every year.  I just toss them out to the chickens/compost.

Ten pounds per plant is awesome!  If I can get half of that per plant I'll be one happy guy!

Good luck!

Excellent!

Thank you Joshua!

I guess I am used to the store bought ones that seem to go bad in a few weeks.   Hopefully these garden beauties will have the health and vitality to hold on until spring.     I am so excited to be able to make my own sweet potato slips for next year!

I'm just catching up here...thanks everyone for sharing experiences and information.

Samantha, 10 pounds per plant is excellent!
Can you share your 'how to'?

As far as curing them, I dig them up and lay them out on paper for awhile in the shade...wipe more soil off of them and bring in the house to lay out on paper some more....at least a week or so but longer doesn't hurt.
I've never understood the use of humidity for curing them...it might be a commercial way for the stores but as you say they don't keep well.
I like to get the skin as dry and tough as possible, then sort by size into cardboard boxes or paper bags.  We have always stored them in our living room where the heat is. Warm, above 55F is good...cold will cause them to rot.

I've had them keep well for a year but we usually eat them earlier.

I had grand(iose?) plans to grow lots of sweet potatoes this year. I started early in a pot on a sunny windowsill...

planted slips out to the garden area protected by a fence...

The deer LOVED this idea, the early leaves are very nutritious and tasty - perfect to help out the local deer population explosion. The fence was no barrier at all to motivated deer.

In the end, the plant in the pot survived, produced about 470 grams of tubers in a pot of about 5 liters.

I'm sold on growing them in pots at this point.  The good I've observed, no bug damage thus far from any of them I've grown in pots, easier to drop them out and find ALL of them easily just by sifting through the loose soil, fairly consistent results, medium large containers seem to be doing better than large, or x-large.
The bad, a lot of very small potatoes, having to use plastic/fabric vs natural soil, having to water them more, and no very large potatoes vs what I've grown in the ground.

Plastic pots vs fabric pots.  Huge difference in the root binding around the plastic pots vs almost no root binding with the fabric pots.  The fabric pots seemed to edge out the plastic pots so far as far as size/yield, but I haven't weighed anything yet so I might be wrong.   In my desert climate (no measurable rain all summer, ultra low humidity, high temps normally between 100f - 105f) the fabric grow bags would need more water compared to the plastic, but the way I did it, the fabric pots actually got much less water than the plastic pots.  I dug out a channel the width of the fabric grow bags about 2" deep, and put a plastic tarp in the bottom and up the sides 2" or so to catch the water runoff from going into the soil beneath and being wasted, I also made sure the foliage covered most of the grow bag so no direct sun could get on the bags once established.

The soil was a bit different in some of the plastic pots as well.  More than half was my homemade compost, and the rest of it was more of a potting mix with a lot of perlite, vs the fabric grow bags were 100% filled with my homemade wood chip compost.

I did fertilize exactly the same, and I used Alaska fish fertilizer (the regular stuff, and also the Alaska "mor bloom"  (0-10-10) every couple of weeks up until about July, and then nothing but water until now.

Joshua, That's a great photo record and results!

I'm having better luck in black 20 gallon feed tubs than in the ground lately but I think I'm crowding them at 3 plants per tub and I'm not feeding them at all.

I plan on more 'green foliage' teas next year as at least some form of nutrition for them.

Judith, yes, you're right.  I think I'm not getting anything huge because I planted two or three slips per container.  Maybe one or two is better.  Thank you also for posting up the info about them.  I had planned on harvesting after the first frost, but when I read that the tubers could be damaged from soil temps below 55f I decided I'd better pull them now since they're in containers.  

That being said, I was WRONG about the plastic containers outdoing the fabric.  WOW!!!  196lbs I weighed in last night!!!  I can't believe it, and I don't expect anyone else to either!  Maybe my maths is wrong......
Plastic containers:  First one I did was 8lbs even, (that was a couple of weeks ago in the first picture I posted).  + 10lb 7.0oz, +9lb 10.1oz, + 7lb 1.2oz, + 10lb 8.2oz, + 12lb 8.8oz, + 12lb 14.8oz.

So the plastic containers totaled 71lbs 6oz at an average of 10lb 3oz per container.

For the fabric I had 6lb 13.5oz, + 6lb 11.1oz, + 7lb 12.4oz, + 7lb 6.1oz, + 6lb 10.5oz, +8lb 2.3oz, + 8lb 1.4oz, + 7lb 12.4oz, + 7lb 14.1oz, + 9lb 7.7oz, + 8lb 5.9oz, +8lb 13.9oz, + 8lb 1.10z, + 8lb 8.2oz, + 8lb 3.0oz.

The fabric containers totaled 124lb 15oz at an average of 8lb 5oz per bag.

I still have about about 20 more plants in the ground to go!  I planted them different than normal, and I'll make a long rambling post when I pull those out.  Oh yeah

I did weigh a lot of the smaller roots that I probably will not eat, and a lot of gumball sized ones, not to mention there is still a fair amount of moist soil on them, so let's just call it 175lbs!!!  :)  Oh yeah, the biggest ones were just under two pounds, so no monsters (probably due to how many slips were in each container).

So I dug up the ones that were planted in the ground yesterday.  My soil here is heavy clay, so I dug a one foot deep, by one foot wide trench, and back filled it with compost so the slips would be happier growing into potatoes, (also so it would hopefully be easier to dig them out).  It was a bit easier to dig them out, but it was still surprisingly laborious, especially compared to having them in containers.

I had a total of 16 single slips, planted about one foot apart.  The far end of the row got a bit of morning shade from my palm trees, so I think that's why the weight of the last few was so little.  The results were fairly inconsistent compared to the pots, as well as being less weight on average.   From the sixteen plants, I got a total of 73lb 9oz, or an average of 4lb 9.6oz each.  
Results each, 5lb 11.3oz, 3lb 8.9oz, 3lb 0.9, 3lb 10.4oz, 2lb 13.3oz, 5lb 8.9oz, 5lb 1.8oz, 5lb 4.3oz, 8lb 1.3oz, 5lb 3.0oz 5lb 1.0oz, 3lb 3.8oz 1lb 2.7oz, 4lb 14.5oz, 2lb 0.8oz, 1lb 10.9oz.
Nothing to complain about, but not nearly as good as the containers.

A whopping total of 269lbs 11oz!!!  My dogs, chickens, and I may turn purple by the time we run out of eating them....

I'm actually thinking about doubling up next year and trying to sell some.  

I grow mine in raised beds. Both beds are 6’x4’x4’. I get between 200 and 250 pounds per bed. I find, that leaving smaller sweet potatoes in the beds, brings larger sweet potatoes the following year. When I do slips, I don’t use the water method. I start them in soil 3 months before I plant them.
Amending the soil with compost and a potassium heavy fertilizer and using irrigation for a steady water supply are important. Also, keep in mind, that if you remove more than 20% of the vines, it will lower the production. That said, the longer the growing season is, the more you will get. Since I started leaving all of the smaller sweet potatoes deep in the soil I have gotten a lot more from each of them. A friend of mine let all of hers grow for 2 years before harvest. She had two beds, and only harvest one each year, so the other continues to grow. Once the vines die down, she cover them with a thick layer of mulch, so they don’t freeze. She also says that she doesn’t harvest them all at once. She digs some up, when she needs some for cooking. She says that it keeps them fresh longer. Eventually I want to try that too, but right now I need the space for my winter crops, since we can grow all year round. Once the kids have moved out, and we need fewer sweet potatoes, I am probably going to do this too, since it means that I don’t have to start slips and will get a steady supply without having to actually restart the production each year.

An idea from our very own Redhawk - " We trellis one sweet potato vine every year because that is the one we pluck leaves from for greens. The others we let grow as they will and bury a node about every three nodes.
Once that buried  node puts out roots, I cut it free of the parent, this sets the new plant into tuber mode so we get more sweet potatoes at harvest time (for us that is November).
Through experimentation I found that this method works far better than leaving a vine whole and just covering nodes with soil.
Once you cut the newly rooting plant from the parent vine, the parent vine doesn't give up tuber making energy to the newly rooted part you snipped free. You have created two slips from one using this method."

Soil temps are an issue.

" Temperature and Crop Development

The plants produced a healthy canopy but never produced tubers. They needed lower temperatures to induce tuber development. The optimal temperature for tuber growth is said to be about 59°F, while for leaf it’s about 75°F.

https://www.researchgate.net/publication/267342035_Temperature_Effects_on_Sweetpotato_Growth_and_Development_Poster_Board_227

The optimum temperature for total biomass production was 30/22 °C (71 - 86 F) - and declined by 9% at 35/27 °C and 27% at 40/32 °C. "

Here in N. FL our  soil temps don't start dropping until October but slips are only available up until June. Makes for a very long growing season. If you dig them before frost (usually very end of Nov.) you won't get much. An early frost like we got last night is a problem. Soon as this cold front is gone it's digging time and we'll see.

Dave Bross wrote:An idea from our very own Redhawk - " We trellis one sweet potato vine every year

I always wondered if sweet potatoes would climb a trellis. My mother used to grow one in a South window just to have something that was cheery green. I didn't climb by itself, but it didn't mind growing to the top of the window.

AND, darn it, I just downloaded an article about AIR GROWING potatoes with drip irrigation in 5 gallon buckets. and I cannot find the article. Oh, just remembered, it was in the book, "The Amish Ways" by Eddie Swartzentruber, Global Brother, 2024. The gist of this is to have the potato on top of the lid with irrigation tubes in the bucket where the potatoes will grow with no soil. Interesting concept! I MAY have to try this as I did different sizes of grow bags from landscaping cloth that I sewed myself, because someone challenged me to do the grow bags. For me they did not work at all. BUT, I also have never really had a good crop of potatoes even from the ground.

When we were kids, my dad would send us to the creek to catch Chubs, Shiners and other 'trash fish.' We would plant a fish in each of the holes with a potato. Dad always grew big sweet potatoes.

Great write-up! I've found similar results with focusing more on soil texture and moisture consistency than on fertilizers. Loose, airy soil and steady watering seem to make the biggest difference for tuber size. I've also had better luck when I limit the length of the vines that actually root,  concentrating energy on a few strong plants instead of letting every runner take hold.
For slips, I've been selecting from the fattest, healthiest roots each season, and those tend to sprout sturdier starts with thicker stems. Mulching with leaves or straw really helps stabilize the soil temperature, too. I'm curious if anyone's experimented with small potassium boosts mid-season (like diluted wood ash or kelp meal). It seems like it could help push tuber bulking without overshooting nitrogen.

Quite a few of the above posts concern growing sweet potatoes in raised beds or in containers.  I would like to propose a hybrid approach.  I cannot vouch for the success of this technique with sweet potatoes - for years I've been planning to someday try it out, but have not yet.  I got the idea after reading about indigenous Polynesian techniques for growing tuber crops.

Construct a large ring that will enclose your hybrid raised bed/container.  Originally, they used stacked stones; I propose hardware cloth bent and tied together into a circle.  It may or may not be necessary to line the interior with weed cloth.  Fill the ring with a loose soil mix.  In sandy soil areas, this could be just pure native soil.  In my heavy clay soil area, I will mix some native soil with some sand and some shredded leaves and with a lot of compost.  Plant your sweet potatoes - or white potatoes or any other large tuber crop you like; don't do regular root crops like carrots or radishes, as this technique would just be overkill - adding additional soil over the season to "hill up" as necessary.

The advantages of this hybrid raised bed/container are two fold.  Compared to an actual container, the advantage is that you can build your ring any size you like.  You are not limited by the size or weight or expense of available containers.  Wish you had a wider or deeper container?  Well, now it is easy to make your own.  Compared to a traditional raised bed, the advantage is that you don't have to dig your sweet potatoes, which process I have in the past found arduous and dangerous to the potatoes.  Instead, at season's end, untie and disassemble the hardware cloth ring, letting the contents collapse.  Then you can just rake through the loose soil to extract the tubers.

Judith Browning wrote:I think allowing rooting along the vines in a longer season works and they will make more potatoes  along there also.  Here, I think it just takes energy away from the main plant.

Here's some photos of information from a book put out by our local extension service for this state...usually good info if we ignore the chemical solutions promoted and they do acknowledge organic growers now😊

Do you have the link to the webpage please. I’d love to pour over this!

Dave Bross wrote:Soil temps are an issue.

" Temperature and Crop Development

The plants produced a healthy canopy but never produced tubers. They needed lower temperatures to induce tuber development. The optimal temperature for tuber growth is said to be about 59°F, while for leaf it’s about 75°F.

https://www.researchgate.net/publication/267342035_Temperature_Effects_on_Sweetpotato_Growth_and_Development_Poster_Board_227

The optimum temperature for total biomass production was 30/22 °C (71 - 86 F) - and declined by 9% at 35/27 °C and 27% at 40/32 °C.

I found these figures surprising - I always thought that the reason why sweet potatoes didn't grow well for me (either in the English midlands on or Skye) was because the temperatures were too low, but 59°F is only 15 Celsius, which we reach even outdoors on Skye in summer. There must be something I'm missing! My tubers are typically smaller at the end of the summer than at the beginning!

I find the abstract a bit confusing.  The eventual size of the storage roots seems to be bigger in the 20-30 C range?

Lisa Sture wrote:

Judith Browning wrote:I think allowing rooting along the vines in a longer season works and they will make more potatoes  along there also.  Here, I think it just takes energy away from the main plant.

Here's some photos of information from a book put out by our local extension service for this state...usually good info if we ignore the chemical solutions promoted and they do acknowledge organic growers now😊

Do you have the link to the webpage please. I’d love to pour over this!

hi Lisa,
the book I have is a hard copy paper one, not online, although I imagine most extension offices have a web site with access to the same information?

as far as temperature goes our sweet potatoes grow well in the heat as long as they have water....summer temps here drop to 60F to 70F at night and 80F to 100F during the day....many are grown farther south where it's even warmer but with irrigation.

BUT, some of the largest I've grown have been dug when the weather has cooled down some, into october, even november if we had no freeze yet...maybe the growth spurt really is that last month or so as I've heard and coincides with cooler weather?

I try to leave until either we are expecting a killing frost or freeze, or until I start seeing signs of vole damage.