Sweet potato success

I’ve been trying to grow sweet potatoes in the northwest for about 5 years now. Every year I got back barely more than I planted in tiny tubers. I tried black grow bags, 15 gallon black plastic pots and various sunny spots. Nothing really worked.

Then last fall we had some trees taken down. After some observation I noticed a spot that now had full sun, was elevated and facing south. It was an old water fountain that no longer functioned and was built on top of a rock. Having read about fruit walls I thought it might be worth trying sweet potatoes there. So I made a terrace with some cedar logs and planted the potatoes. I watered them a few times and then mostly forgot about them. This summer wasn’t particularly hot so I figured I’d get back the usual low yield. I dug them up today. Turns out I was right about that spot being warmer. I haven’t weighed the tubers yet but one plant gave me back easily 5x what I’ve normally seen.

I’m beyond happy about this! Hooray for permaculture emphasizing observation’

When they find their happy place, look out.  They're practically invasive.  Good for you!  I'm glad you finally got the harvest you've been wanting.

Thanks Marco! I was almost ready to throw in the towel on them this year. I kept hearing from people locally that growing them is impossible.  I’ve got a hunch about 2 other places that might be warmer. My fig trees there keep their leaves a few weeks longer than everywhere around them. I’ll try planting there and see what happens in the spring.
Now that I’ve got confirmation that spot is warmer I’m wondering if i could gamble with some satsuma seedlings.
Knowing the microclimates of your property is super important.

I was considering using sweet potatos as an edible ground cover around and under new grafted fruit trees.  I am in 7b in NCarolina.  As the trees mature they will naturally block the sun and decrease the yield, hopefully transitioning to a fruit yield. I am encouraged by your persistence shown in trying to locate the sweet spot for your potatoes to thrive.  Any thoughts on this strategy?

That's awesome, Chris!  I wish that we could grow sweet potatoes year round in zone 6 unprotected.  I just bought a 30x100 greenhouse that will be heated.  Once I get it up, I plan to attempt to build some type of small vertical system in which I can grow them year round.  

We've tried those grow bags. and maybe because its fall, though it has been sunny, and all the sprouts died.  Their in full sun, but the nights have been really cold (down to 28F).  Any suggestions?  
We're starting winter soon in Maine and I can bring the bags and totes of plants indoors, but I have no grow lights or green house, and the garage is not insulated.  I know where to plant them next year, based on the great ideas that Chris had about a sunny spot by my old rock wall.  Full sun and plenty of warm ground.  They should love it!
I'm trying to grow potatoes, winter lettuce, spinach, sweet peas, beets, onions, leeks, and several kinds of peppers.  They're all coming inside for the winter since they are in totes and pots, but without a grow light, and the light from my one window probably won't be enough.  Water and warmth aren't a problem.  
Help please! :)

@Moria Teekema Do you have a greenhouse or a low tunnel?  If you do, I would suggest that you take your pots outside and stick them in there on warm days.  

(TJ) - I wish we had a grow tunnel and/or a greenhouse.  I'm going to see what I can put together with some spare plastic and left over PVC pipe.  Thanks!

I realized after my original post that I didn't do a very good job explaining what I had done.  Here's some additional photos showing that miraculously the sweet potatoes under the fountain are still alive.  This is after probably 4 nights slightly below freezing.  After reading about fruit walls years ago I started looking for spots around my yard that faced south and collected slightly more heat than elsewhere.  The real test though is planting a plant there that is heat loving and seeing what happens.  Since sweet potatoes are so easy to propagate in the spring by cuttings I generated a lot of small plants and placed them in most of the spots I thought were the warmest.  This spot under the water fountain turned out to be the best.  

You can see in the photos that it's elevated and facing south.  We have a wind that comes in the winter from the east and they're sheltered by the fountain and the raised soil.  The sweet potatoes have an almost unobstructed view facing south.  The benefit they're getting from being elevated and facing south isn't perfect.  You can see that only a tiny portion of the plant has survived below freezing temps.  I doubt they'll survive the winter.  I'm in zone 8b so it doesn't get that cold here to begin with.  

Ken - Yeah I think that will work out well for you.  I used to grow sweet potatoes in Philadelphia when I lived there.  They pretty quickly form a ground cover.  Winter cold nuked them every year so I'd have to replant.  I'd imagine you'll have to do the same.  The warm in NC should cause them to spread pretty quickly in the spring.  It can't hurt to try.  Sweet potatoes are easy to propagate.  

I think sweet potatoes will do great in some parts of NC.

Nice one plant harvest Chris. Very nice. I've been tinkering with sweet potatoes a couple years. So far they have been easy to grow & make good looking ground cover. The leaves are very tasty too.

This is my first go at growing sweet potatoes. I received 7 slips from Southern Exposure Seed Exchange back in the second week of June. I followed the planting instruction provided describing depth and spacing and planted them directly into a compost pile. From what I've read about harvesting sweet potatoes is to wait until leaves on the vines begin turning yellow. Today is Oct. 25, and in my zone 7b southern climate, nothing is turning yellow yet and the vines are still green and growing, and it's also been just over 120 days since I planted the slips. I went out this morning to pick a sweet potato to see how they're doing.  Within the shade of the leafy sweet potato vines and poking out of the top of the compost pile I eyed several sweet potatoes. Little did I know it was the tip of the iceberg. Much to my surprise and humor, I pulled an elephantine sweet potato, measuring 15 inches long and weighing 9.5lbs.

James Freyr wrote:This is my first go at growing sweet potatoes. I received 7 slips from Southern Exposure Seed Exchange back in the second week of June. I followed the planting instruction provided describing depth and spacing and planted them directly into a compost pile. From what I've read about harvesting sweet potatoes is to wait until leaves on the vines begin turning yellow. Today is Oct. 25, and in my zone 7b southern climate, nothing is turning yellow yet and the vines are still green and growing, and it's also been just over 120 days since I planted the slips. I went out this morning to pick a sweet potato to see how they're doing.  Within the shade of the leafy sweet potato vines and poking out of the top of the compost pile I eyed several sweet potatoes. Little did I know it was the tip of the iceberg. Much to my surprise and humor, I pulled an elephantine sweet potato, measuring 15 inches long and weighing 9.5lbs.

Wow, I'm jealous!  I planted some from Southern Exposure last April and much to my dismay I think woodchucks ate them.  

Chris Holcombe wrote:I’ve been trying to grow sweet potatoes in the northwest for about 5 years now. Every year I got back barely more than I planted in tiny tubers. I tried black grow bags, 15 gallon black plastic pots and various sunny spots. Nothing really worked.

Hi Chris, what kind of sweet potatoes did you plant and where did you get them? When do you put your slips in the ground? I'm north of you in the Tacoma area. Our home is in a little microclimate that seems to be slightly warmer and sunnier than the surrounding areas.  This spring I tried sweet potatoes for the first time.  I put them in a raised bed that gets full sun.  The vines did well but I only got pencil thin tubers except for one palm sized one.  I know I'm slightly colder than you but your success gives me some hope to try again. :)  I think I'm going to try in black pots closer to the house so that they get the heat that radiates off the house at night.

Did you try growing them again this year?

This was my result from an 8' row. I think I might try using a plastic sheet next year to make a mini greenhouse in the spring and fall. My dad is farther north than me and did that and got tubers big enough to eat.

I looked up my journal notes for what I planted. I believe it was called “Japanese”.
Here’s my notes from the year before I posted this:
Redmar in black plastic pot with plastic on top: 8oz.  One yielded 11oz!
Oak leaf in black plastic pot with plastic on top: 7oz One yielded 11oz!
Japanese in black plastic pot with plastic on top: 8oz
Frazier white: in black plastic pot with plastic on top: 7oz
Willow leaf: in black plastic pot with plastic on top: 9oz

I have another note saying oak leaf did the best, followed by willow leaf and then japanese.
I’d be interested in breeding them from true seeds but I can’t seem to get them to actually make any seeds after flowering. I’m not sure why.
This year I wasn’t able to try growing them again. I was sidetracked too much with the puppy I got in January. Maybe next year I’ll order new slips from the preservation center and try again.
I’ve also been on the look for tubers that can either overwinter when there’s abundant water or ones that are very drought tolerant. Cassava seems like a possible solution but I failed to get it to root the first time I tried.

I have the strange feeling that the new home of your sweet potatoes was the spot for success.

one question:
Did you have in the area before a lot of green potato slips growing but only tiny tubers? Then you had definitely too much nitrogen in the ground.

In the place near the fountain all the plants and the potato slips size telling me that the spot is a pretty poor soil and especially nitrogen is scarce.
(may be washed out as the fountain was still operating?)

Our sweet potatoes are also some giants and the spot is the worst for any other plant as there is barely something growing at all...

as above mentioned, sweet potatoes are a weed and hard to control and small tubers are the result of too much love and food...
Plant the slips, forget them and bring a bigger basket at harvest time...  

See Hes wrote:... Then you had definitely too much nitrogen in the ground...  

So I wasted my nicely fertile bed on my sweet potato experiment? Oh well, it was an experiment! So maybe I'll try again in the bed I grew corn in this year it's a very sunny warm spot and the corn sucks almost all the nitrogen out of the soil. I just won't add any compost or fertilizer to that spot for next year.

Jenny Wright wrote:

See Hes wrote:... Then you had definitely too much nitrogen in the ground...  

So I wasted my nicely fertile bed on my sweet potato experiment? Oh well, it was an experiment! So maybe I'll try again in the bed I grew corn in this year it's a very sunny warm spot and the corn sucks almost all the nitrogen out of the soil. I just won't add any compost or fertilizer to that spot for next year.

Hi Jenny,

Sweet potatoes in Thailand:

-Sunshine and heat can't be enough.

-Sandy loam to red loam which is in the Udon Thani till Mahasarakham area common but it should drain well or at least raised so the water can run off.

-Fertile yes but low nitrogen levels.
We throw a thin layer rough compost on top. (our compost is not purposely made, we just scramble some dirt from underneath the trees or from a pile of cut greenery left laying in situ.
Long fresh cut grass works well when you plant the slips and keep the top two leaves above the grass mulch layer which we then let overgrow by the vines.

-constantly humid but not wet or waterlogged (That does actually the grass mulch because as I said, once planted we just don't bother anymore.
As we have no winter we pass by the field and if we fancy a few sweet potatoes we are looking out for thick segments where the vines touch the ground. Underneath is always a big potato to find.

- If you do all right another problem comes:  
You definitely need to try to keep the vines from invading the entire area.
Fry a chopped onion in a sauce pan until its glassy, then add the chopped sweet potato vines to it, a bit salt a sizzle of sugar and nutmeg to taste, Boiled sweet potatoes aside and 2 fried eggs on top and Popeye will kick your door in ;-)  = end of invasion

I have tried to grow all kinds of sweet potatoes after bringing them back from travels-- usually with minimal success (I've got hard rocky clay, so they go in bags or large barrels).
Last year I decided to face the music and just grow them for their leaves, which I (and the rabbits) love. Planted them in a crummy corner of the garden that is full of rocks and can't be used for anything else. We ate the greens all summer and into the fall, and when they withered at the end of the year I was astounded to find over 10 pounds of good, edible sweet potatoes pretty much pushing themselves up out of the clay underneath the leaf mulch. I had not even imagined I would get any, but I did. From a single plant, in miserable soil, with lots of sweet potato bugs and no care. I just put in my slips (from one of the harvested potatoes) this week, and am going for more leaves again this year, hopefully I'll get some nice surprise tubers again too.

Here's an update. I harvested my sweet potatoes today, November 2nd. It turns out I grew sweet potatoes and a rabbit. Many of my sweet potatoes were rabbit tested and approved, evidenced by all the little piles of rabbit poop under the vines. Some were badly eaten, and some had just a few bites taken out, and some were fortunately left untouched. I did abandon some of the worst looking sweet potatoes, a couple goliaths which appeared to be more than half eaten. My harvest ranged in size from giant 7-10lb size all the way down to fingerling. All total I took in 81lbs of sweet potatoes.