· Brent Wilson's Answer
· Without seeing the plants and the soil they are planted in, it's hard to say precisely what the problem is with your Dwarf Burford Holly. If you have watered the plants every day, it shouldn't be that they are too dry. But the symptoms and effects you describe could be caused from the roots and plant drying out. That being said, new plants would have to go several days, or even over a week, to dry out like this. It might take a month or two for well-established plants to dry out.
If the problem is not caused from too dry of soil, the other possibility is that the soil is too wet. Consistently wet and mucky soil can cause root rot that then causes leaves to turn black and eventually fall off the plant. This is a process that usually occurs over a period of time when there has been too much rain or the plant roots are just sitting in wet soil.
If it's not a soil moisture problem, it could be over-fertilization or the effects from spraying with too strong a solution of insecticide. If the plants were extremely root-bound in the containers they were growing in this could cause transplant shock. If plants are rootbound the roots should be loosened. Transplant shock can also occur as a result of the plant being fertilized daily with liquid feed at a growing operation, and then being transplanted into the ground without receiving it's daily "fix."
At our nursery, we refuse to sell plants that have been grown and juiced with liquid fertilizers. Instead, we only carry plants that have been grown and fed with slow-release granular fertilizers. Unfortunately, at the big box store chains, many of the plants they sell have been liquid fed.
As for a remedy, I would pull one of the plants out of the ground to check for soil moisture. If the soil is too wet, and there's not much you can do to dry it out, you'll need to replant all of them with about half or more of the rootball above ground level. Then build a mound of soil around the rootball that starts at the top edge of the rootball and tapers gradually to ground level. This will keep the roots above the water table so they can grow down to it instead of standing in it.
If the soil is too dry, water more regularly until average rainfall resumes and cooler weather sets in. Apply a two-inch layer of landscape wood mulch to help hold moisture. To rejuvenate the plants that have lost a good deal of foliage, pruning about 1/3 of the height of the plant would help as well, then applying a well-balanced, slow-release shrub and tree food.
Hope this info helps.)