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Troppofoodgardener
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When to harvest Sweet Potato?

We've been growing sweet potato since June, and when we last dug into the soil (about a month ago), we dug up a sweet potato that was roughly the size of tennis ball. However, it was white and not the usual pinky-brown colour.

I've been told that sweet potato comes in different colours, and obviously there would be different varieties of it. So if I have the white variety, how do I tell if it's ready for harvest? Is it a matter of leaving it in the ground for a number of weeks/months, or can you tell by looking at the vines and leaves above ground?
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Typically, they require 120 to 140 days from planting, depending on the variety and how warm the growing season was. You want to harvest them before a killing frost comes, as this frost can damage the potatoes.

[url=https://www.lsuagcenter.com/en/crops_livestock/crops/sweet_potatoes/LSU+AgCenter+Horticulturist+Discusses+Curing+and+Storing+Sweet+Potatoes.htm]Here[/url] is some information on curing and storing them after you harvest.

Hope you get lots of potatoes :).
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The way I see it, they're big enough to harvest if they're big enough to eat. Since they don't all grow at the same rate, if you can do it, just harvest the ones that look ready and leave the others to grow some more.

I've read that you don't want to leave them in the ground after the ground temp drops to under 55ºF. HOWEVER, if you live in areas that freeze, ones that are left in the ground will just break down and become fertilizer for next year's garden. :wink: I've had really great growths from crops planted in last year's sweet potato bed. :D

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I have never heard that about harvesting before the ground temp is 55. :hide:

I have always heard to harvest them when the leaves have yellowed to abut 1/3 or before frost which will damage them. If you have a surprise frost you can cut off the tops early in the morning and harvest that night if you don't have time in the morning. The spoiling effect of the damaged leaves quickly effects the tubers so that is why you would cut off the tops.

As stated they are long term plants and also they can be harvested at any point or even a selective harvest like Apple said.

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pods.dasnr.okstate.edu/docushare/dsweb/Get/Document-1098/F-6022web.pdf
Harvesting ... If the crop is to be stored, harvest before frost for maximum yields. If soil temperature fall below 55ºF some damage to the quality, storability, and slip production of the roots will result. Chilling injury can result even though a frost has not occurred.

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Thanks everyone for the harvesting tips. I live in the tropics, with weather much like Florida. So there's no real threat of frost! :)

Some of the leaves on the plant have turned yellow, but nowhere near to 1/3. I'll try digging another one out, and test out the theory of "If it's big enough, it's ready" ;)

It would just feel weird eating a sweet potato that's not pink/orange/brown!
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Nah, ya gotta start eating all those weird roots people use throughout the world. Some of them are gray when cooked which will look weird to you the first few times.

Boniato is sometimes called a sweet potato, but is a lovely white fleshed tuber cooked like potato or sweet potato. It's drier, mealier, and less sweet than a standard sweet, but can't be mistaken for a regular white potato. In Florida, we get our liking for boniato from our Cuban population, but it's definitely grown throughout the Caribbean.

So your tubers have been in the ground for maybe 120 days. I'd see if longer helps, but it probably won't change the color any. Even tiny sweet potato roots are orangish inside.

My paltry sweets this year grew from bits of root not harvested last year. The foliage hasn't started yellowing, but has slowed down. Not that it was doing well last month either... Very poor soil with no attention from me this year in that area. I've had a few finger length, just right for throwing back into a more enriched area of the yard to see what comes up next year.

So Troppo, you're actually growing sweets throughout your winter? That probably puts you about USDA zone 11. Most of Florida is 9 or 10. I'm 9b: could not grow sweets in winter due to the occasional light frost.

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[https://www.sandhillpreservation.com/pages/sweetpotato_catalog.html]Here[/url] is another way of determining when to harvest sweet potatoes (scroll down to "Growing Sweet Potatoes").

The author claims that a sweet potato reaches what he considers to be an acceptable size when it receives 1200 heat units.

These heat units are calculated by adding the high temperature of the day and the low temperature of the day, dividing this number by 2 and they subtracting 55 (I suppose since sweet potatoes don't do well below this temp). The resulting number is the heat units for that day.

What do you all think of this method? I've also heard of it being used for growing tomatoes.
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I believe 90 to 100 days after planting of some varieties and the temperature issue holds true - anything below 30 degrees and they are ruined,under 55 and they are injured,however, no damage will occur unless frost injures the top exposed root.
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For me, it's best to know the average "days to maturity" of the Sweet Potato variety being grown, and record the expected maturity date on the calendar.
I grew Beauregard this year, which indicated a 95 day maturity. I dug most of the potatoes at about 100 days, and they were great.
The plants were still robust, with vibrant green leaves. If I had waited until the leaves started to "turn", I bet the potatoes would have been too "big and woody".

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OK, I fixed the link. [url=https://www.sandhillpreservation.com/pages/sweetpotato_catalog.html]Here[/url] is the site.

I think a less tedious way to use this method would be to look at the average days to maturity and then gauge if you had an average, cooler, or warmer growing season, and adjust your harvest schedule according.

I've never heard of sweet potatoes getting woody if left to grow too large. I've had some big one and they were still tender and very good. Perhaps it has to do with variety.
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thanrose wrote:
So Troppo, you're actually growing sweets throughout your winter? That probably puts you about USDA zone 11. Most of Florida is 9 or 10. I'm 9b: could not grow sweets in winter due to the occasional light frost.

I tried figuring out what USDA zone i was in, but seeing that it's regularly 33 degrees Celcius here, I think I'm off the charts! Sorry for mixing up Florida weather with the Oz tropics. I spent one too many humid afternoons in Miami during summer maybe!

Right now it's officially Spring in the rest of Australia, but where I live, that really isn't helpful either. We only have 2 seasons: Hot & DRY, or Hot & WET. There's a tonne of rain on its way, so we're quickly approaching the Wet season. I just don't want to leave those sweet potatoes in the ground too long, as they'll rot.

Read all those other posts on "Heat Units" and that sorta makes sense. Well it's been hot here every day, so I guess the potatoes are more than ready. Still haven't dug them up due to being busy with other projects.... :oops: I will soon!!
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Troppofoodgardener wrote:
I tried figuring out what USDA zone i was in, but seeing that it's regularly 33 degrees Celcius here, I think I'm off the charts! Sorry for mixing up Florida weather with the Oz tropics. I spent one too many humid afternoons in Miami during summer maybe!

Right now it's officially Spring in the rest of Australia, but where I live, that really isn't helpful either. We only have 2 seasons: Hot & DRY, or Hot & WET. There's a tonne of rain on its way, so we're quickly approaching the Wet season.
Sounds like Panama, where we lived for three years when I was a kid. Two seasons: the dry season and the rainy season. Never cold or even really cool. Tropical. 9 deg. North latitude.

I'm not clear at this point which months the rainy season was, but it seems that the year was divided into approx. five months dry and seven months rainy, give or take, for a given year. And the "rainy" season was sometimes measured in inches per hour (2.5 cm/hour or more).

Is it possible that what you're growing is a true yam (Dioscorea batatas) rather than a sweet potato (Ipomoea batatas)? If so, that might account for the color.

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Cynthia raises a good point, you may very well be growing true yams.

As far as the heat units go, it sounds like you should have had plenty of heat. Let us know how big your potatoes are when you take a look at them. If they're still not good size, you may very well have some type of a variety other than a sweet potato.
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Ok.. dug up one of these babies today, and it's looking very similar to the one we dug up a couple of weeks ago.

Here's a pic, including measurements. Notice the big green patch on the bottom right hand. I've been told not to eat any potato with green bits on them, as they're cancer-causing. Does anyone know if that's true??

[url=https://img708.imageshack.us/i/swpot1.jpg/][img]https://img708.imageshack.us/img708/7107/swpot1.th.jpg[/img][/url]

Here's a close up of the potato.. it has some very faint purplish spots developing in its 'eyes'. Not very clear from the photo I'm afraid..

[url=https://img541.imageshack.us/i/swpot2.jpg/][img]https://img541.imageshack.us/img541/3372/swpot2.th.jpg[/img][/url]

And lastly is a pic of the current state of its leaves. Is there much difference between a true yam's leaves and sweet potato leaves?

[url=https://img35.imageshack.us/i/swpot3.jpg/][img]https://img35.imageshack.us/img35/5508/swpot3.th.jpg[/img][/url]
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OK, I'm no expert, but I'm going to say from what I've seen, you don't have a yam.

It's often hard to find solid information on them online, since they are so often confused with sweet potatoes.

First off, although yams come in a variety of shapes ans sizes, they usually have a think skin that looks almost like bark. And, although there are some small ones, they can grow very large, up to several feet in length.

Secondly, have a look at [url=https://www.google.com/images?hl=en&client=firefox-a&rls=org.mozilla%3Aen-US%3Aofficial&biw=1366&bih=588&gbv=2&tbs=isch%3A1&sa=1&q=yam+plant&btnG=Search]these photos[/url].

Look at the top row of pics, you will see a few plants that look like tropical trees, with large, broad leaves. I suspect that these are true yams while the other leaves are merely those of sweet potatoes that were incorrectly labeled as yams.

To further support my hypothesis, [url=https://tungkinfoongsblog.blogspot.com/2009/01/elephant-ear-plant-alocasia-macrorrhiza.html]here[/url] is a site where the owner shows a plant that he says closely resembles a yam plant. It, too, has these broad, upright leaves.

What do you think?
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Yams / sweet potato / taro... it's all a little confusing! It may be that what we in Australia refer to as a sweet potato may be different to what it's called in the States? :? Or maybe I'm growing a WHITE sweet potato?

I know what is called taro, and from the pictures i saw of the Elephant ear plant, that definitely isn't what I'm growing. When I cut open the alleged 'sweet potato' it didn't have the purplish fibres you see inside a taro, nor did it have thick brown skin.

Anyway, if interested, here is a link of other discussions on yam vs. sweet potato:

https://ask.metafilter.com/76604/Yams-vs-Sweet-Potatoes-Wheres-the-value

However, the vine from which i originally grew the plant came from a local gardening guru. (she has grown food in the tropics for many years, published a book and hosts a segment on a national gardening show) So i'll have to take her word for it! :wink: Thanks for all the help however everyone! :D
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Troppofoodgardener wrote:Yams / sweet potato / taro... it's all a little confusing! It may be that what we in Australia refer to as a sweet potato may be different to what it's called in the States? :? Or maybe I'm growing a WHITE sweet potato?

I know what is called taro, and from the pictures i saw of the Elephant ear plant, that definitely isn't what I'm growing. When I cut open the alleged 'sweet potato' it didn't have the purplish fibres you see inside a taro, nor did it have thick brown skin.

Anyway, if interested, here is a link of other discussions on yam vs. sweet potato:

https://ask.metafilter.com/76604/Yams-vs-Sweet-Potatoes-Wheres-the-value

However, the vine from which i originally grew the plant came from a local gardening guru. (she has grown food in the tropics for many years, published a book and hosts a segment on a national gardening show) So i'll have to take her word for it! :wink: Thanks for all the help however everyone! :D
Well, it sounds like you got it from a more then veritable source. I'll bet you have a special variety of sweet potato! If this lady is really into her gardening, then I'm sure she likes the "exotic" stuff.

Cook it up and let us know how it tastes. If you don't post back we'll all be able to agree that it was just some kind of poisonous plant that resembles a sweet potato. :lol:.
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green part of potato edible?

haven't cooked it up as yet or tasted it as I'm a bit unsure about the green patch on the tater. (look at pic)

I didn't get any answers on whether the GREEN parts of (any) potatoes are carcinogenic or harmful. Does anyone know/care? :?
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Hmmm. IF what you have is indeed what we think of as "sweet potato" -- I.e. ipomoea -- then my GUESS is that greenness on the tuber (though I've never heard of that on an SP) is safe since sweet potato leaves and stems are edible, unlike the "Irish" potato in the solanacea family.

It's not a wild potato (Yamaimo) right?

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You could also just cut the green patch away to be safe.

Apps, just when I think I've gotten the whole sweet potato/yam thing down, you throw something new at me :p......wouldn't have it any other way :wink:.

I don't think this is what Top has since he said he got the start from a very experienced gardener.

Well, I'm off to research it, anyway.
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Here's a photo of ones grown in Okinawa and southern islands of Japan, a sub-group called "Daisho" or "Yamuimo" (or "Yamanmu" in Okinawa dialect according to the caption) which are not the long tubers that is commonly seen in the rest of Japan. These are very hairy! :lol:
[img]https://blog-okinawa.img.jugem.jp/20091004_939703.jpg[/img]
https://blog.okinawa.pya.jp/?eid=790088

Some Daisho varieties are purple inside:
[img]https://blog-okinawa.img.jugem.jp/20091004_939668_t.jpg[/img]
I want to try growing these purple ones. I believe Kitazawa seeds had seed potatoes last year but they would only ship within California. :(

I'm more familiar with the white-fleshed long-tubered or flat hand-shaped yamaimo, but I believe the fresh flesh tend to turn reddish brown when they are exposed to air and become oxidized.

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Definitely isn't a "Yamaimo"... This potato is very pale and thin-skinned. Almost like a regular potato except it's an off-white colour.

I STILL haven't eaten it yet... got way too much other produce to munch through at the moment :P

Another gardening friend said it's a "white" sweet potato. Maybe i'll have to contact the local gardening guru who gave me the vine and settle it once and for all! :wink:
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Troppofoodgardener wrote:Definitely isn't a "Yamaimo"... This potato is very pale and thin-skinned. Almost like a regular potato except it's an off-white colour.

I STILL haven't eaten it yet... got way too much other produce to munch through at the moment :P

Another gardening friend said it's a "white" sweet potato. Maybe i'll have to contact the local gardening guru who gave me the vine and settle it once and for all! :wink:
That's exactly what I was thinking about suggesting! I think that may be the best, most definitive option. Perhaps you could show her the potato or email her a pic?

Until then, [url=https://www.google.com/images?q=white+sweet+potato&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&source=univ&ei=LyHITKC9FoL-8AbR6InJDw&sa=X&oi=image_result_group&ct=title&resnum=2&ved=0CCwQsAQwAQ&biw=1366&bih=588]here[/url] are some pics of white sweet potatoes :).
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Troppo, the green part of Solanum tuberosum, or Irish type white potato, the ubiquitous one of mash and chips and bakes, has the bitter principle solanine in it. You can eat tiny bits of it, such as on the edge of a potato chip or crisp and recognize the bitter flavor without any harm.

There are two other things sometimes called sweet potato. One is Ipomea batatas and is the sweet potato of Southern US fame, with variable foliage, sometimes ornamentally colored, and sprawling vines. The flesh of the tuber is generally orange or yellow. The skin of the tuber will be orangey- to garnet brown in most varieties. There will be a milky exudate when you dig or cut the skin. That cures in a few weeks of storage dependent on your climate. The boniato I referred to from Florida and Cuba is a white fleshed Ipomea batatas that is drier fleshed, not as sweet, and white to creamy flesh of the tuber with a golden or beige skin. It can look rather like a general baking potato of Solanum tuberosum with smooth skin. I think your expert would have given you this one, Ipomea batatas, and it is the boniato variety with the white flesh. Also possible that it is kumara, the Maori name for I. batatas which can come in gold or orange skinned tubers.

The other is the yam or llame or name (with a tilde over the n) that is sometimes confused with Ipomea batatas. Yam/name/llame is Dioscorea spp, several of which are eaten throughout the world. If you have this genus Dioscorea esculenta and Dioscorea trifida are possibilities. I'm still thinking your expert was dead on calling it sweet potato, and that it is an Ipomea batatas.

I've intentionally grown both Ipomea spp. and Dioscorea spp. in the past, but the latter only as nonedible curiosity. That genus has several invasive species in my part of the world.

Also I'm pretty sure that the green part of the tuber is not poisonous or a problem, given that it is Ipomea.

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garden5 wrote: That's exactly what I was thinking about suggesting! I think that may be the best, most definitive option. Perhaps you could show her the potato or email her a pic?

Until then, [url=https://www.google.com/images?q=white+sweet+potato&oe=utf-8&rls=org.mozilla:en-US:official&client=firefox-a&um=1&ie=UTF-8&source=univ&ei=LyHITKC9FoL-8AbR6InJDw&sa=X&oi=image_result_group&ct=title&resnum=2&ved=0CCwQsAQwAQ&biw=1366&bih=588]here[/url] are some pics of white sweet potatoes :).
Pics #2 and #5 look VERY similar to the type of sweet potato i have. And I finally ate the darn thing (without the green bits)! It does taste sweeter than regular potatoes, and has a somewhat denser texture. It's basically like eating an orangey-pink coloured sweet potato. Maybe a bit less sweet? Or it could have just been my imagination... :shock:

Cheers for the input as well thanrose :) yes, the plant has sprawling vines and it also climbs. Has the milky substance when stems are cut.

I have also emailed said gardening expert and and will hopefully hear from her soon. We will then be able to confirm once and for all if it's the Ipomea batatas or not!! :lol:
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I kind of saw the resemblance to yours in a few of the photos as well.

Looking at the pictures of the plant that you posted, it does look like a traditional sweet potato plant. I'll be you've got a white one :o.

I'll be waiting for the update :wink:.
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The final word

Well I received an email response from the local tropical gardening expert.

She says:

"It is just a cultivar of the normal white sweet potato - called Oenpelli White."

Apparently it was produced by the local agricultural department in the '80s to grow in tropical climates such as ours in the north of Australia.

Oenpelli (now more commonly known as Gunbalanya) is an Aboriginal community on the eastern border of World Heritage listed Kakadu National Park at the base of the Arnhem Land Escarpment.

I have also looked up some info surrounding sweet potatoes grown in Australia (and other parts of the world), apparently there are three varieties according to the article below:

https://www.abc.net.au/gardening/stories/s1664919.htm

Also according to the local expert, the best way to harvest this potato is to look for a thickened stem going into the ground, which will indicate a growing tuber.

Off I go to do more harvesting then! :P
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Cool, thanks for the update. Let us know how you like them.

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The mystery is solved :clap:!

Glad to hear what you have is something edible. Let us know how they taste when you have some.

Here's wishing you a great harvest.
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