There are brown and black spots on the back of the leafs. Could you tell me what is causing it and what can I do to correct it? Thank you.
Crown of Thorns
Certified GKH Gardening Expert
This is normally caused by overwatering. This is an easy fix though. the leaves that are affected already will retain the spots, but the new growth will be fine. Although it will not cure the damage done already, it will prevent it from spreading.
The treatment that I recommend for this is to add a few capfuls of peroxide to the next watering. You should let the soil dry out almost completely between watering.
This article will refresh you on the care of this plant: https://www.gardeningknowhow.com/houseplants/crown-of-thorns/crown-of-thorns-houseplant.htm