Sweet Potatoes

[ameno]

This is question I've been wondering for a while, but at what temperature do you find sweet potatoes stop any meaningful tuber growth, and therefore may as well be harvested?

For the past three years, I've been growing them in pots in my conservatory. All the stuff I read says for crops outdoors, dig up when the leaves are touched by frost, and for crops under cover, harvest when the vines start to yellow and die back.
Problem is, that has never yet happened. The vines always remain green and healthy. Year before last, I got bored of waiting and harvested them in early December, and the leaves where still green and healthy.

They're a sub-tropical crop, though, so even if they survive in cooler temperatures, there must surely be a point where it is too cold for them to really grow much, even if it is not cold enough to kill them (and my conservatory can get pretty chilly in the winter, although it never freezes).
So what is that point?

[roitelet]

I have them in the border of a poly tunnel. From what I have read they take 4-5 months to produce tubers. Mine were planted in June from slips taken from an organic commercial sweet potato so I have no idea what variety they are. It seems that they shouldn’t be watered for three weeks before harvesting. I stopped watering on the 1st October and will dig them up at the end of the month. There are some showing at the base of the plant stems. At the moment the vines still look fairly good although not quite as green and fresh as when they were watered regularly. The tubers are not produced until towards the end of the growing season.

I will report back when I have lifted them.

[ameno]

Mine in the conservatory (I planted them at the beginning of May) already have some pretty large tubers on them, based on fumbling around in the pots. One is poking halfway out of the compost, and looks to be at least half a kilo in weight.
The top growth is growing rampant, too. Real triffids. They have smothered almost all of the windows and a quarter of the roof, and have also escaped through every open window and are colonising the outside walls.

I could probably harvest them now, but I want to leave them as long as possible, to allow them to grow as big as possible. Hence the temperature question. I want to know at what point there would be no point in leaving them longer, as they wouldn't get any bigger.

I've got three in the ground at the allotment, too. Those will obviously have to come out sooner, probably after the first light frost kills the leaves.

Also, before your plants die completely, I'd advise taking cuttings and rooting them, then overwintering them. Saves buying new ones next year, and it's easier than sprouting a tuber. I did it last year, and they seem to have done really well.

[Vegi potager]

First time growing them this year so cannot offer advice as was pretty poor showing so far.

First lot: Beauregardsupposed to mature in 90 days had lots of fat roots (not tubers,) scraped with a spoon and roasted made some tasty oven chips sadly only 350gm from 1 plant. Now obviously I was too keen. So am waiting on bonita which is supposed to be ready 105-110 days and Muraski (120 days) (all went out into a pop up in potato growbags 2nd week of May.)

I think my main failures for larger yield were watering or lack of even though the pop up was always looking to be well humidified; and 2, my previously mentioned temptation to harvest. According to the supplier I should get 5kg in total from the 3 plants. So am hoping for at least 1.5 kg each from the others. ( I have always been over optimistic, which is why I garden!)

They are just beginning to show signs of yellowing so have 5 cuttings from each in the kitchen. Each cutting is 30cm long with roots coming from each "side shoot" along the length. Hoping to pot up leaving just the top few leaves showing and overwinter on a sunny windowsill. Too expensive to buy slips each year and these cutting have been surprisingly easy to take. Planning on trying again next year if I don't manage to do anything stupid over the winter, cos these things really want to grow in spite of me

[ameno]

I found cuttings easy to overwinter, so they should be fine. Just don't overwater them.
Also, they will probably be a bit potbound by next spring, so your best bet, rather than planting them as-is, is to either root prune them before planting, or give them a liquid feed and move them somewhere warm early April or so, and then take fresh cuttings from the new growth and use those cuttings for you actual plants.
I did both this year, and they seem to be doing well.

Also, if you're growing in pots, I'd actually recommend keeping cuttings short. They seem to produce most tubers from the roots sprouting from the lowest point on the stem, so if you plant long cuttings you end up with all the tubers cramped up in the bottom of the pot. I grew some long and some short last year, and the long ones were all like this.
I'd recommend no more than 3 inches below soil level,
Small cuttings do just as well as long ones in the end. In fact, the one this year which seems to be doing best was from a cutting only 2 inches long in total.

[Vegi potager]

Thanks for the advice Ameno, I need all the help I can get !

[ameno]

Sweet potatoes root from cuttings incredibly easily. Even the tiniest piece will root and grow if given warmth and moisture. I don't know why more people don't just take their own rather than buying expensive slips each time.

[bikermike]

oooh, how does one take cuttings? is there a how-to somewhere?

I have some growing in the greenhouse, and it'd be nice to keep them going if it can be done.

[ameno]

oooh, how does one take cuttings? is there a how-to somewhere?

I have some growing in the greenhouse, and it'd be nice to keep them going if it can be done.

Just snip off a length of new shoot about 3-6 inches long, strip the lower half of leaves, and put it in water until it roots, then pot it up. In fact it doesn't really even need to be a new shoot. Practically any piece of stem will root from the leaf nodes.
They root incredibly easily. You should see root growth within 3 days of putting then in water, as long as they're somewhere warm.

The plants don't like the cold, so need overwintering somewhere above about 10c ideally (although I had mine in my conservatory last year, which went down to 2c on cold nights, and four out of six survived), but not too warm so they don't grow too much. A cool room within your house would probably be ideal.

[bikermike]

ooooh! that's a plan for this weekend...

(I'm quite enjoying the sweet potatoes in the greenhouse, they grow exuberantly and anarchically - they even mug the cucumbers)

[Vegi potager]

oooh, how does one take cuttings? is there a how-to somewhere?

I have some growing in the greenhouse, and it'd be nice to keep them going if it can be done.

There will be a video (or several 100) out there on the interweb thingy somewhere. Basic instructions: you cut off the growing end, trimming of leaves to leave just 2-3 on the top stick em in a jar of water on a sunny windowsill and roots will grow at every side shoot where you trimmed off the extra leaves. (mine only took a couple of days to start.)

Follow Amenos instructions for more details... I will be