Leaves of Crown of Thorns Falling Off

I have a very large crown of thorns. I've had it 10 years or more. In summer, I have it outside and it flourishes. Normally when I bring it in the fall it loses most of the foliage and then starts blooming again.  This year it is just forming green leaves that quickly dry up and fall off.

Dry leaves always lead me to investigate watering and fertilization practices.  If you haven't changed your watering practices you might need to check the root environment to make sure it has not changed.  Potbound plants do not have enough soil to hold moisture causing leaves to yellow, brown and eventually drop. Though cacti and succulents like to be potbound they occasionally need to be repotted.  Carefully slide the plant out of the pot.  If the roots fill or encircle the inside of the pot it is time to transplant.  Loosen the circling roots before moving the potbound crown of thorns to a slightly (1") larger container.  Adjust watering as needed. Overwatering can also lead to yellow leaves.  Make sure the pot has adequate drainage and the plant doesn't sit in excess water.  Not the problem?  Look at your fertilization practices.  Too much fertilizer can damage plants.  Limit fertilization to when the plants need it.  Poor growth, lack of vigor and pale leaves can indicate the plant needs a nutrient fix.  Cacti and succulents need limited fertilization.  Fertilize only when needed and during their active growth period from spring through summer. 

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