I'm in zone 6. I have several flower-box style plastic planters with different kinds of mint in them, and 2 or 3 of them are wilting significantly. The two that are wilting the most are the spearmint and the chocolate mint.
These planters are about 2 ft x 9 inches, and I used Miracle Gro organic potting soil to plant them. The planters were outside in pretty full sun, and I've been watering thoroughly daily.
I went on vacation for a week, and a friend was watering my plants. About day 4 or 5, she noticed the spearmint wilting significantly and moved it under the deck, where it receives some sun through the decking and then gets about maybe 4-6 hours of sun in the late afternoon.
When I got back in a couple days later, it became clear that my spearmint and chocolate mint were having real wilting problems, although the lemon mint, orange mint and peppermint were all doing just fine in the same spot. After some quick research that made me wonder if they were getting too much sun and drying out, I moved all mints under the deck.
After a couple of days now under the deck and watering, the spearmint and chocolate mint really don't seem to be getting much better, although the friend who was taking care of them says they look better than they were when she noticed the problem.
Any suggestions here?