container orange defoliation
I have 2 container orange plants about 12 years old growing in 12 gallon pots, the larger about 6x5 feet. They stay in a sunlit inside room during the cooler seasons and outside during the warmer. Two years ago, the pot of one of them developed drainage problems and the tree defoliated and ended up losing about 2/3 of the branches. My salvage efforts at the time included changing both trees to larger pots, enlarging and increasing the number of drainage holes and changing to a faster draining mix. Both trees steadily improved over the past 2 years, and the larger set a large number of blossoms which began opening earlier this month. Then about 4 days ago, the larger tree began to defoliate especially new upper leaves and unopened blossoms. It has since lost about 3/4 of its leaves. At first, I suspected inadequate watering and gave extra, but leaves continued to fall. I then pulled the tree up out of its pot to examine the roots and medium. The tree was not rootbound, There was no trapped water and the medium if anything looked dry and the roots looked dry and in poor condition. The other tree sits right beside and is unaffected. Over the years, I've neglected the watering of this tree on many occasions and it had never defoliated, so I'm hesitant to chalk this up to just inadequate watering. Might it be that during the blossom period orange trees are particularly sensitive to water requirements and much more prone to defoliation than at other times? Or am I missing something?