Japanese holly and Boxwood have a very similar leave and habit. Telling them apart requires that you look closely at the plant.
Japanese Hollies and Boxwoods
Japanese holly (Ilex crenata) has a very different leaf form to European holly. They look and behave far more like boxwood than holly. So when I unearthed a few large bushes in the garden, I was forced to look at the leaf structure to decide which was which.
In essence to tell the difference you need to look at how the leaves are placed on the stem. A boxwood (Buxus) has opposite leaves along the stem. Holly, on the other hand has alternate leaves. Both have elongated, smooth leaves that are about ¼” – ½” in length and both have a similar green color. The holly though has a few very small spines toward the tip of the leaf. Holly will also flower in the summer, though it may not be seen as against boxwood which flowers in the spring. The fruit from Japanese holly is black rather than red and does not show up as well as red against the foliage, so may be missed.
