It's Sweet Potato Time!

[GoDawgs]

Wow! There be some monsters in there! These are probably the biggest sweets I've ever grown. We ended up with 46 lbs of sweet potatoes from 11 hills. These are 'Jewel', a nematode resistant variety I've been growing for years.

24.09.04 Sweet potatoes, 46 lbs.JPG

Now it's time to cure them for two weeks and let all that starch start converting into some sugar!

[MissS]

That's a great harvest. Did you do anything different to get such large taters?

[AKgardener]

Love it

[GoDawgs]

That's a great harvest. Did you do anything different to get such large taters?

Nothing that I can put my finger on. I was wondering that too so I checked the '23 garden maps to see what had been grown in that bed previously.

Spring and summer '23 there were zinnias and other assorted flowers. They didn't get fertilized much.

Once the flowers were gone, in Oct '23 I planted leeks on one side of the bed. My notes say that just before planting I had mixed into the row 6 oz of 5-10-15 and a drizzle of superphosphate for the 18' row. The 5-10-15 was based on something I had read earlier and the superphos was just something I do sometimes with my onions.

This May after the leeks were gone I prepped the bed for the sweet potatoes by pulling some soil from each side to the middle to make the planting ridge down the middle of the bed. Maybe there was some leftover fert in the soil from the leeks? Unfortunately my notes don't mention anything about planting prep for that date but I have a Word document where I keep various plant specific "instructions" gathered over the years. It includes various fert formulations, timing, etc. For sweet potatoes it says:

"A fertilizer formula of 5-10-10 or 8-24-24 works well for sweet potatoes. You can begin fertilizing sweet potatoes about 2 weeks after transplanting them into your garden. After that, they can be fertilized every 4-6 weeks during the growing season. Stop fertilizing about 3 weeks before they are harvested. Generally, 3 doses of fertilizer throughout the growing season are sufficient."

I don't remember doing that so I also checked a "Treatments" spreadsheet where I keep data on all fert or spray treatments (when and what was applied to what plants). No sweet potato fert listed. I might have splashed a little bit of Miracle Grow one time around the young slips after they had gotten used to their now home.

There are only two possibilities left. The first is that I've been following the sweet potato growing advice from a small seed company up in Asheville that says they keep their sweet potato vines cut back to 6' so that all the energy goes into the potatoes. But I've done that for the past several years and have never gotten a crop like this.

Then there's the possibility that the intense heat we had over the summer really pushed forward the growing degree days needed for a harvest so that the 120-135 DTM happened earlier than usual. These were dug on Day 121. Maybe the potatoes "grew" for a longer time than they actually did! Who knows? Wish I could figure it out.

[Gardadore]

Enviable!! They look great!

[GoDawgs]

OK, I had to go down the Growing Degree Day (GDD) rabbit hole. These are heat units calculated from the high and low temps of the day. Sweet potatoes need 1200 GDDs to reach "mature" size. I wonder what is considered a mature size for sweets. Everybody probably has their own idea about that.

Anyway, since I already have highs and lows for every day in my historic weather data it was simple to set up a spread sheet, put in the temps and formulas and calculate how many GDDs this year's crop got. OMG! From the time I planted the slips on May 7 until the day I dug the potatoes on Sep 4 we had accumulated 3046 GDDs! The 1200 number was reached on June 28. Hmmm, if I had dug a hill on June 28 I doubt the sweets would be very big. OK, then I ran a sheet on last year's GDDs. By comparison, last year's crop had 2916 GDDs. Not too much difference and the sweet potatoes were smaller.

If anyone is interested in calculating GDDs, it's pretty simple. Here's a good site about them:

https://extension.psu.edu/understanding ... egree-days

I'm thinking about keeping track of GDDs next year from the time of planting to when they reach 1200 and then digging up one hill just to see what's what.

[worth1]

I read an article by an expert about growing sweet potatoes in the north.
Can't remember the guys name but many of y'all have heard of him.
I imagine he's long gone by now.
Very big in the gardening world of breeding and so on I think.
He basically said you can plant them too soon.

[GoDawgs]

@worth1 , you're right about that. Soil needs to be 60+. Sweets are so sensitive to any little frost or cold soil that I guess by the time the soil is 60, most chance of either is gone.

[worth1]

@worth1 , you're right about that. Soil needs to be 60+. Sweets are so sensitive to any little frost or cold soil that I guess by the time the soil is 60, most chance of either is gone.

I just wish I could remember that guys name.
He was a potato expert and might have been a member of the other forum but he was mentioned a lot there.
He had a great article on the potatoes they used in Belgium to make fries.
Something we don't get here.
The vines are also edible and I've made salads with the leaves.
Our cows loved them.
They would like up when they saw us harvesting sweet potatoes like hungry dogs.
Our beef steer hot the very best of our garden scraps every year.
It was nothing like the so called grass fed beef they sell.
The fat was very yellow and tasty due to this diet.

[worth1]

I just remembered the man's name.
It's Tom Wagner.

[JRinPA]

Can definitely plant them too soon, here. This year they went after my cloche house came out of that spot. I almost always have something in for the spring before the slips get planted. This was almost better, having a greenhouse - when it was too hot for that, it was hot enough for sweets. No worry about peas needing another two weeks before harvest, etc.

Clearly that degree day formula does not apply without correction for Georgia. I've read the formula before...seem to remember it as being fairly linear. I see it as more of a reassurance that if you meet that minimum number, you can probably get a decent yield. I do not take it to mean that if it is super hot, your sweet potatoes will be done early. The DTM will still matter.


So I just read that psu blurb.
@GoDawgs what did you use for the high cutoff? And did you use a low cutoff? I personally don't believe that formula is correct in applying a low cutoff as additive instead negative modifier....

[GoDawgs]

So I just read that psu blurb.
@GoDawgs what did you use for the high cutoff? And did you use a low cutoff? I personally don't believe that formula is correct in applying a low cutoff as additive instead negative modifier....

The base number was 55. Can't remember if I got that from the PSU site or other.

[BlackKrim]

It sounds as if growing sweet potatoes anywhere is a bit of a chore, they seem to be kind of fussy - is that correct? I'd stick with sweet winter squash, myself, if I lived in any of your areas where sweet pots. are doable. Indeed, here in growing area 3, winter squash does well and is easy. JMO.

[GoDawgs]

Actually it's just the curing that takes a bit of attention and that's only two weeks. Planting is easy, an inch of water a week like most other stuff and you can let the vines run like you would squash. I just prefer to train them up a trellis as a space saver. Winter squash here is a no go for me. Too many SVBs to kill the plants, even the moschata types. Oh how I'd love to grow some butternuts but not a chance. Been there and failed too many times. So sweet potatoes are the fill in. Plus they last a lot longer in storage, at least down here where root cellars are pretty absent.

[JRinPA]

Manitoba, I don't know, that is a pretty weak sun. Try it in a hot raised bed, and probably under plastic for more warmth.

They are easy to grow with enough warmth, but they need warm. The big problem I have is voles. Voles love sweet potatoes.

I grow butternut every year too.