When I was a kid, my mom would always note a holly tree and say – “That holly must have a partner nearby.” At that age, I was intrigued by this secret relationship that this holly had that only my mom knew about!
The holly is an example of a dioecious tree. That means the sexual system of an individual specimen is binary, either male or female. It has to have another plant nearby of the opposite gender to reproduce.
In dioecious trees, the male tree distributes pollen from its staminate flowers and the female receives pollen on their pistillate flowers. This is a necessary action to bear fruit. Without pollination, blooms will still form but the fruit cannot form, neither can the seeds to produce the next generation.
Other examples of diecious trees include the aspen, bayberries, boxelder, date palm, ginkgo, holly, kiwifruit, Osage orange, mulberry, papaya, persimmon, pistachio, red cedar, spicebushes, sumacs, white ash, wax myrtles, willow. There are many others. It is estimated that 29% of trees are diecious.
The rest fall in the other three types of systems: co-sexual, monecious, or polygamous.
But let’s stick with the holly for now – because this is important to factor in dioecious plants for a well-planned landscape.
Hollies are often used for developing a hedge along a property line or as a visual backdrop for a garden. They are deer resistant due to their prickly leaves. And their evergreen nature provides for both color and vegetative screening year-round. The show-stopping female hollies produce a gorgeous display of red berries in the winter months.
And for those berries to form, sexual reproduction must take place. It doesn’t mean a male has to be planted directly beside a female, nor does it mean multiple males are needed if there are fewer than ten females. It only means there must be at least one male plant in the vicinity of that hedge – ideally within 50 feet for winterberry, or within 500 feet for evergreen holly.
So how do you tell male and female hollies apart?
It’s not easy. The easiest way is to look for berries on a female plant. But you can also look at the flowers, which are located between the branch and leaf joint. The male flowers have four yellow/white stamens extending from the center that support the anthers, which are pollen sacks. The female flowers have a green ovary (berry-like bump) in the center of the bloom. When pollination doesn’t occur, the female will drop its blossom and not produce berries.
Before I remove a damaged dioecious tree from a customer’s yard, I always pause and check – am I cutting down another tree’s partner? If so, I tell them to not let it stay lonely for long.
Manor Tree Service has been working as professional arborists in the greater Glen Arm area for over 40 years! Our clients love our complimentary tree evaluations to identify any issues that may need to be addressed or managed.