I don't think you can treat them like Dahlias. If you see basal growth of white new stems, this means that the plant was not hardened off or is too warm.

You will have to allow the new growth to green out in order to replace the storage that was used to grow them, and to form new fine roots, which will be needed when it breaks true dormancy in the spring. Too much wet with cold will kill them.

Here is a copy of a response I gave from another forum

Overwintering in a basement or a garage of a tuberous sage is more likely to be successful if the temperatures will be around 35 - 40 degrees.

The bulkhead (I assume this is the same structure as a hatchway, a covered stairs leading upward from a basement to the outside and not usually insulated) is essentially a covered cold frame collecting residual heat from a basement. For those of us with basements, these bulkheads are ideal storage areas.

The only caveat is to add a little heat for really cold nights. Guaraniticas are much more durable than patens, which are very fussy about storage.

Remember that tuberous sages do not have nodes (eyes) on them, and need some attached stem with nodes to reactivate. This section of stem is the most vulnerable part of the dormant plant and can rot out, making the tuber useless as a means of resuming growth.

Salvia guaranitica survives every winter here with a good mulch of shredded leaves. S. g. 'Omaha' is more tender, but is fairly reliable with mulch.

Hi all,

Has anyone ever managed to make a salvia patens survive a Canadian winter in zone 5 or colder?

If so, apart from mulch, what is needed?

-ChrisL