Answer: I'm not sure if you're referring to herbal sages (Salvia sp.) or to the Texas sages/Rangers (leucophyllum sp.), both of which are commonly called sage. However, you're right that neither of these plants would like roots sitting in wet soil. Good drainage is essential. We had so much rain in November that even if you cut back on watering, your soil may still be wet several inches below the surface, especially if it is heavy clay. Stick a soil probe (any long thin piece of metal) into the soil and see where it stops. It will move easily through wet soil and stop at dry soil. For leucophyllum, you should be able to reduce watering in the winter to once every 3-4 weeks. Salvia would probably need more frequent watering, depending on soil conditions.
Also, some dieback is normal in the fall. If you don't think wet soil is the problem, please send another email to the Q&A site (not to my email address) with more description of the problem.
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