Old leaves does not matter. Good root system is most important + young shoots. They will be happy in the tunnel, but direct hot sunlight is even better.

I guess raggy/dead old leaves have been cut off. Some older leaves remaining are still sick.

New season started, hot weather conditions: https://i.imgur.com/wahFrIm_d.webp?maxwidth=640&shape=thumb&fidelity=medium Some of them don't like high uv level, but I think it will be fine: https://i.imgur.com/ji6jhw1.jpg Special containers for sweet potato: https://i.imgur.com/Itlmidu.jpg

No any dogs or cats here, so I guess my plants are safe

10 days ago:




Now:




They grow very fast.

First roots appear in soil:



No any single shot though. So, need to keep waiting. It's still alive, maybe it will wake up. It takes long time, as I can see. Either it will grow or it will rot away, there is no other scenarios

I think you will eventually get slips, worth to try. End of January/begin of Febrauary is good time to start to get slips at the spring time, ready to plant. It usually takes 2-3 months for them to arrive and grow. In most cases, roots appear first, so be patient.

It's time to another experiment. Some people recommend to try wit soil, this way: https://i.imgur.com/Ot501Tr.jpg https://i.imgur.com/OjvxKQv.jpg https://i.imgur.com/5SySJnO.jpg https://i.imgur.com/9dM3PDj.jpg January 23th today, they say it should take not less than one month until first shoots arr...

It looks healthy, 45 cm tall, +10 cm/each 2 weeks:


And, other small guy:


Both of them grow since November, rooted from old plant's green. 10 died, one barely alive, remaining 2 are healthy

Link is nice, but it does not say anything where to buy Canadian variety. Btw regarding to cold, -20 tomorrow expected here

Do you know new variety from Canada?
https://european-seed.com/2018/12/a-new ... he-market/

If it grows just fine there, it is suitable for all temperate zones. Canada is not warm country

Hard to say. Sweet potato definitely does not like to stay indoors. All of above is more my guess why, there may be more factors. The fact is, some plants are able to grow indoors just fine, some others, not. Sweet potato is rather second group. You can't grow it as home plant, you can only try to k...

Current humidity is 35%. You should not care about low humidity in my opinion. Worst things are lack of daylight and lack of wind or draft. All of it causes inability to dispose water by leaves. Especially, young small plants are affected by oedema and all leaves die eventually. I think that's becau...

How do you think, any chance it's going to survive winter indoors? 10 are dead, this one has decided to grow. That's my last one.

As you are located in UK, you are probably never getting winter frosts. That makes a lot of things easier, especially if you also own tunnel. I am experiencing even -10 or -15 frost sometimes - even greenhouse or tunnel is useless when outdoor temperature is so low. From my experience, sweet potato ...