Why are the leaves on My St Johns Wort turning red?
I moved it because it was getting dry too fast. It\'s in a NE window and leaves The leaves turned red. Too much sun? Would a W window work better?
Certified GKH Gardening Expert
St. John's Wort will handle full sun with no problem. Red foliage is common with a phosphorus deficiency. If you are using miracle grow with slow release nitrogen, then this can be the cause. This tends to lock out phosphorus for awhile to allow for uptake of nitrogen, which in this case is not a good idea.
If you are using a low fertility soil, then this can be a general deficiency. I recommend feeding potassium phosphate, or a bloom formula feed with less, or very little nitrogen than an all purpose.
This article will give you more information on the care of these: https://www.gardeningknowhow.com/edible/herbs/st-johns-wort/st-johns-wort-plant-care.htm