Anyone know?

With not much to do, laid up with the lurgy, I’ve thought about this and have changed my mind to Day Lily tubers. That would also go with the long leaves.
They definitely need to be in full sun.

Not a dahlia leaf more like the agapanthus leaf but the tubers are not big about an inch to inch and a half I ll try and get a better photo tomorrow too dark at the moment
Yes it ll be a nice surprise if they do flower this year

They do look like dahlia tubers but 'tall thin green leaves' doesn't sound like dahlias, more like agapanthus. If you type agapanthas bulbs or dahlia tubers into google and then select images you will see some pics which may help you decide.

They don’t look like agapanthus or dahlia to me. They look more like the cultivated bluebells I have to dig out every year. That would explain why there are so many of them in the pot because they’re very prolific reproducers.

Difficult to be sure though without knowing more about the size of bulb and leaf.

Dahlia is my answer too.

Definitely not nerines Lemongrove I ve got a garden full of them they are quite different bulbs to these tubers and I ve also got Montbrezia and it’s not them either

Would also say dahlias..

Yes the pot. It will act like insulation.

Hi J52 - so I wrap it around the pot rather than the plant itself? The pot is a sort of concrete low urn shape about 18 inches square.

Dahlias I think, definitely not frost hardy!

Could be nerines?

Sorry just had another look, they're not Crocosmia.
Whatever they are will be a nice surprise next year!

No idea, they look a bit small for agapanthus ( although if they are, they like being crowded in a pot) so, how tall do the green stems grow?

I think that they could be Crocosmia. They very soon become overcrowded and stop flowering.
If you plant out and they stop flowering eventually, then you have to break up the clump and they will flower again.

Gladioli's ?

Iris's ?

I was going to say dahlia's too.

I think it would be ok. Just watch out for extremely cold weather. If it’s forcasted, wrap some bubble wrap around the pot.

I have just put a "boxberry" into quite a large concrete container. It says it is hardy down to -10 degrees. Not sure whether I might have done the wrong thing.

Yes, the pot gives little protection to the roots as they are all close to the edge of the pot. Wet compost freezes close to the roots, all around the pot.

Ground planted roots are protected by soil layers and frosted soil tends to be on the top.

Are [plants in containers more at risk of frost damage?

These look like dahlia tubers to me.

Some Agapanthus are liable to frost damage and if container grown need to be protected from extreme cold. Easily done by covering with horticultural fleece or popped into a sheltered corner.
They do well in the garden in moisture retaining soil. They do need summer sun to flower, so an open aspect is best.
This year’s sun has been great for them.

What is a frost-free container please?

I have 2 clumps in my clay soil, one near a hedge which flower poorly and others in a more open position which flower really well. They are both better since I needed the pot for something else and thought I'd try then in the garden!