It’s hard to know, but it could be the excessive heat. They prefer temperatures around 60 to 80F. When such days occur, it might help to provide a little shade. Mints do like moist soil, but not overly so. During hot days, it may appreciate watering twice a day, but check the soil first to make sure that it isn’t soggy. Overwatering often appears on the plant as yellowing wilting leaves that feel soft, and also soggy soil. Underwatering, the leaves are crisp and brown, with dry soil. If the plants are very crowded, your mint might also be under stress, as the roots like to spread. Also make sure they haven’t been overfertilized, which sometimes turns leaves brown.
You can trim off just the browning leaves.
It’s hard to know, but it could be the excessive heat. They prefer temperatures around 60 to 80F. When such days occur, it might help to provide a little shade. Mints do like moist soil, but not overly so. During hot days, it may appreciate watering twice a day, but check the soil first to make sure that it isn’t soggy. Overwatering often appears on the plant as yellowing wilting leaves that feel soft, and also soggy soil. Underwatering, the leaves are crisp and brown, with dry soil. If the plants are very crowded, your mint might also be under stress, as the roots like to spread. Also make sure they haven’t been overfertilized, which sometimes turns leaves brown.
You can trim off just the browning leaves.