By Kerry Ann Mendez
Are you frustrated that despite your best intentions to see your holly covered in red berries, there are zilch? Assuming the shrub is planted in the right spot and you're pruning correctly, it may just need a partner. Some shrubs are dioecious, meaning male and female flowers appear on separate plants, and therefore cross pollination must occur for seeds or berries to appear.
Both evergreen (Ilex meserveae) and deciduous hollies (Ilex verticillata) fall into this category. Many cultivars are clearly labeled to insure you that they are a good matchmaker. For example, 'Blue Prince' dates 'Blue Princess' and 'Mr. Poppins' pairs with 'Berry Poppins', but sometimes the relationships aren't so clear.
Ilex verticillata 'Jim Dandy' will cross with many ladies, including 'Red Sprite', 'Berry Heavy', 'Berry Nice' and 'Afterglow'. No comment on that one. If you are not sure which hollies are compatible couples, be sure to ask an Estabrook's nursery person for help.
Both male and female hollies will produce flowers, but with closer inspection, you can determine if the flowers are female or male. Male blooms have four stamens in the center while the female has a small green bump (pistil). The flowers will appear in late spring, so you might want to take a peek at your berryless hollies to see what partner is missing in action.
Lastly, don't make the mistake of assuming it's a one to one ratio (one male to one female) for dioecious shrubs. In many cases, one male can cross pollinate ten or more neighboring females.