have had claret cup cactus from sw Colorado approximately 15 yrs old. It usually has 25- blooms in spring. for past two years, blooms form but never fully open. what could be problem. cactus stays outside in middle Tennessee.
Claret Cup Cactus
Certified GKH Gardening Expert
Excess salts that build up in soil can cause this.
A fresh cactus soil mix can help the cactus.
Disease or pest can cause buds to abort.
Don't move the plants around during buds forming.
Make sure the cactus is getting adequate sunlight and heat.