I don't know what your zone is, but I'm zone 6a and I prune a Salvia greggii no later than late Summer and wait until late Spring the following year to insure hardiness of the Salvia. Sometimes a Salvia greggii will survive our Winters.
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I'm not familiar with Salvia greggii 'Strawberry'. I'll have to do a search for that one. Sounds like a beauty!