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The American holly, Ilex opaca, is celebrated for its berries in shades of red, orange and yellow and its glossy green foliage and perfectly pyramidal shape.
The deciduous holly (Ilex decidua) and the winterberry (Ilex verticillata) lose their leaves but reveal thick clusters of berries along their stems for dramatic effect through much of the winter. Once the berries come ripe enough for the birds to eat in February, they are usually gone in a day.
These are three of the more striking plants in our landscape during the winter months. Those berries can’t be beat.
If you are a plant that is celebrated for its berries, then great disappointment occurs if you fail to produce, and sometimes hollies fail to produce. If you have a holly that fails to produce berries, it may be a pollination issue.
One male holly will effectively pollinate three female hollies within a hundred feet. However a tree up to a mile away can pollinate female trees if the conditions are ideal. Pollination is an issue with hollies because they are dioecious.
Stearn’s Dictionary of Plant Namesdefines the term “dioecious” as having the male reproductive organs born on one plant and the female on the other. This is an important definition for plant lovers to understand because it will tell us whether we need a pollinator in order to get fruit. This certainly applies to many of our orchard trees; but it also applies to some of our favorite ornamentals, particularly hollies.
Warm spring weather is ideal for pollination because insects are more active, but cool spring weather means that they are not. Bees, ants, wasps and night-flying moths are among the insects that aid in carrying pollen from one tree to the next.
If the weather is on the cool side, they will not be efficient pollinators. A late-spring frost also will eliminate a season of berries if the flowers are damaged.
Another fruiting problem may be that your holly is male and will never bear because of its dioecious nature. But, please, please, do not take an axe to a male holly out of frustration. He may be the only male in the neighborhood for all the other females in need of some pollination.
So how do you tell the difference between male and female hollies? You have to wait until spring, when they are in bloom.
The flowers produced on male trees appear in groups of three or more, and those on female trees are born singly. The flowers are distinctive, as well. If you look into the center of the female flower, you will see an ovary-like, pistillate in the interior of the flower.
The male flower is staminate, meaning that there is no round, ovary-like component to the flower, only stamens that emerge from the flower center. You get the picture.
If you are certain that your holly is a female but you are still waiting on berries, it may be that the tree is still a bit too young. Seedling hollies take anywhere from 5 to 10 years before they fruit. Give them a chance to reach puberty.
Another way to tell the difference between the male and female of the Ilex genus is to go by the cultivar name. Many of the female cultivars have feminine-sounding names like “Judy Evans” and “Jersey Princess,” with male pollinators in “Jersey Knight.”
But this is not always perfectly clear because my all-time favorite American holly is “Chief Paduke,” and she is definitely a female, full of bright red berries by Thanksgiving.
Your best bet is to check always with your local nursery about which cultivars are needed in your landscape, and you could make a holiday visit to Bernheim Arboretum to see its American holly collection, considered one of the best in the United States.
Check out gardening columnist Jeneen Wiche’s work at www.SwallowRailFarm.com. You can find her columns also at www.SentinelNews.com/agriculture. She answers questions once a month in SentinelNewsPlus. To submit a question, send an E-mail to firstname.lastname@example.org type “Sentinel-News” in the subject field.