How cold can it get in your region @Nollie ? I have heavy soil where mine are planted I did add extra compost and probably sand.
I dug up my apricot spite agastache last year for over winter protection, all of them died . My mum left hers in the ground with no protection all of them survived and are doing well
So far, @Perki -8 has been the low, plus heavy snowfall the beginning of this year, frequent torrential rain. Nights do get very cold at my elevation up so waking up to frost seems to be the norm in winter. Often followed by lovely sunny days though.
Sorry you lost your Sprite - I think, like your mum, mine stand a better chance in the ground as my house is too warm and my unheated poly had ice on the inside last year, so they are probably better left in the ground. I hope!
Mountainous Northern Catalunya, Spain. Hot summers, cold winters.
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I dug up my apricot spite agastache last year for over winter protection, all of them died . My mum left hers in the ground with no protection all of them survived and are doing well
https://www.rhs.org.uk/Plants/313009/Agastache-Blackadder/Details
Sorry you lost your Sprite - I think, like your mum, mine stand a better chance in the ground as my house is too warm and my unheated poly had ice on the inside last year, so they are probably better left in the ground. I hope!