I've always loved holly especially around Christmas time. I once hand carried a holly wreath home on an airplane after a trip to Seattle. Not wanting to do that too often, I decided I would have to get a holly tree.  I found I would need two trees a male and a female if I wanted berries. My local nursery kindly ordered them for me. (Note this was at least a decade ago). 
     These being my pre- Master Gardener days, I am not sure what variety of holly I have. I suspect it is either Ilex aquifolium, English Holly, or an English Holly cross breed.  I put them promptly into containers where they languished for the next several years.  I finally decided I had to do something so I transplanted them into the ground in my side yard.
     Both trees perked up immediately.  The male tree which got put in the shadier spot is about three feet tall. The female who ended up in the sunnier spot shot up to five feet.  Over the past year or two I was able to pick some sprigs to put into arrangements, but I was afraid to cut too much and didn't have many berries.
     This year the female tree  has exploded with berries.  I even cut enough branches to make my own small holly wreath.  (I now realize why we don't use holly at the wreath workshop, you need major protection for dealing with those spines.)
     I've been trying to watch the berries, but I haven't seen any birds eating them yet. One Internet source suggested that the berries needed a few freezes to soften.  I am going to continue to watch and will see what happens. Robins and mockingbirds are supposed to like them.