Thyme and mint come back just fine for me. Sage....not so much.

Maybe it's the variety. Maybe it's the location in your garden. Maybe it's how much you mulch. Heck....I dunno.

Linda

Can you describe what you mean by a self-contained permanent planter? Is it a raised planter or bed. If the plants are near the edge of a raised bed they may not be getting enough winter protection.

It's a raised barrel planter. Thanks for responding. Can you recommend anything in particular that might help?

Is it possible to move the barrel into a garage over winter? That might help you gain some extra hardiness. Plants in containers don't have the protection that plants in the ground do.

If you can't move your barrel you could try placing bags of leaves around and over it for extra winter protection. Another option would be potting up small pots of your herbs and keeping them in the garage over the winter. I have not had much success trying to overwinter herbs indoors. Rosemary survives but the others die.

Thanks for the suggestions. I guess I hadn't considered that they might be less protected in the planter than they'd be in the ground. I might have to re-think what gets planted where this year. :)

(For what it's worth, I had great success with overwintering some of my herbs indoors this year in my hydroponic Aerogarden. I'm really pleased with how this worked out, as I too have had trouble keeping herbs alive indoors in the winter in past years. However, I didn't do this with the thyme, sage, or mint, as I had hopes of them surviving the winter outside...)

The rule of thumb over on the bonsai forum is that you plant something two zones hardier that you otherwise would when overwintering outdoors in pots. Therefore, in a zone 4 area, you'd need plants rated down to zone 2 to survive in your set-up.