Crown of Thorns cactus
have had the plant for years always have trouble getting it to bloom now the plant has yellow spots all over all the leaves. It is almost 4 ft. tall. What is wrong. ( I have 8 more cr. of thorns but they all have smaller leaves, this one has large leaves0 what is the difference?
Certified GKH Gardening Expert
Newer cultivators have larger leaves then older varieties.
Crown of Thorns are susceptible to fungus issues. You can use a fungicide on the plants.
Bacterial leaf spot can also be found on these plants. The disease is characterized by circular gray to brown leaf
spots surrounded by distinct yellow halos. The infected leaves often turn
yellow and fall off the plants. Leafs should be removed from the plant and disposed of. Make sure the plants have adequate air circulation.
Avoid getting water on the leaves and stems.