It seemed to happen almost over night. Leaves on ground are green, not yellowing. Another holly bush 20 feet away is fine. Have had these bushes for years without a problem.
Disease or infestations would usually show some other indications on the plants.
Damage to leafs or discolorations.
Could the plants have been had an accidental spray from a herbicide?
Also if the plant is suffering from drought it could drop leaves, but generally yellowing of leaves would precede this event.
How much sun does a holly tree need? I am going to buy one.
Plan on a full sun planting location.
Here are some links for you.
https://www.gardeningknowhow.com/ornamental/shrubs/holly/common-types-of-holly.htm
https://www.gardeningknowhow.com/ornamental/shrubs/holly/common-types-of-holly.htm
The leaves on my holly bush are disappearing. In some areas, all that remains are stems which eventually die. Out of 50 plants, 6 have been defective. Two of the plants are together but the others seem random. The leaves do not appear to be eaten or fallen to the ground.
There could be many reasons for the die back of Holly.
Inspect the plants carefully for more clues as to the issue.
Look for insects and or damage to leaves.
Remove any dead or diseased material and clean up the fallen leaves--dispose of this material.
Here is a link that lists the most common insects and disease.
Should I spray them with winter spray and rap with burlap? Every year all the leaves turn brown and fall off in spring.
Winter damage is a common problem for Holly growers.
Since you have had issues each year, I would certainly go ahead and use a
anti desiccant spray.
Follow the directions on the solution.
Also creating a barrier from the wind will help. I don't recommend wrapping the Holly tightly; rather create a circle of burlap around the plant using posts. Leaving space between the burlap and plant allows air flow and the plant won't heat up when the sun shines.
https://www.gardeningknowhow.com/ornamental/shrubs/holly/leaf-scorching-in-holly.htm
https://www.gardeningknowhow.com/plant-problems/environmental/winter-burn-in-evergreens.htm
https://www.gardeningknowhow.com/plant-problems/environmental/protecting-plants-winter.htm
What kind of holly do I have? How should I trim/prune it? Thank you!
Here are some links to help you identify your holly and pruning information.
https://www.gardeningknowhow.com/ornamental/shrubs/holly/common-types-of-holly.htm
https://www.gardeningknowhow.com/ornamental/shrubs/holly/how-to-tell-the-difference-between-a-male-and-female-holly-bush.htm
https://www.gardeningknowhow.com/ornamental/shrubs/holly/trimming-holly-bushes-how-to-prune-holly-bushes.htm
Do holly bushes grow well in Southern California? Hot, dry summers and some very cold winter nights. How best to plant and grow a holly bush in a pot? Thanks.
The variety of holly called Toyon is a good shrub for your growing zone.
Hardy down to -15 degrees F.
Here are some links on care requirements.
https://www.gardeningknowhow.com/ornamental/shrubs/holly/common-types-of-holly.htm
https://www.gardeningknowhow.com/ornamental/shrubs/holly/growing-holly-bushes.htm
Can I transplant a wild holly tree in the winter? It's been out of ground since early Nov. I think my daughter dug it up from the woods. Can I transplant the holly tree now or keep in 5-gal bucket with dirt to cover roots and keep in garage that has no heat?
I would keep the pot in the garage for the winter.
Check the soil throughout the winter and add a small amount of moisture if the soil begins to dry out to much.