THE BIRDS AND BEES OF HOLLY TREES.
With Valentine’s Day quickly approaching folks are looking for love! Lots of individuals are looking for partners, and we aren’t just talking about people. Many varieties of plants need partners in order to produce fruit and berries, including the holly. A holly’s berry display creates great winter interest so ensuring that berries are produced is vital if you want a winter landscape that stands out. Let’s jump into the reasoning behind the need for hollies to find love!
Most all hollies are dioecious meaning that male and female flowers are on separate plants. Berries are only produced on female plants when flowers
have been fertilized by the pollen from a male flower, usually with the help of bees or other pollinators. There are, however, a small number of holly varieties that have adapted and found other methods of reproducing.
One way of producing berries without the need of a male plant is through parthenocarpy, the Chinese Burford Holly being a key example. With parthenocarpic hollies female flowers develop berries without having been fertilized with pollen. This process produces a sterile, or seedless, berry which may not be helpful for carrying on the genetic line but is great in your landscape. Parthenocarpic hollies can still be fertilized and can produce much larger displays when a compatible male holly is present. Finally, there are a select few hollies with perfect flowers, these are most notably the Oakland and Oakleaf hollies, perfect flowers are those with male and female parts. These hollies not only self-pollinate but they can be used successfully as pollinators for the more common dioecious holly. So, what if you have found what you thought was the perfect match for your beloved holly and it still is not producing berries? Let’s take a deeper look at the factors that contribute to berry production.
Assuming the specimen you have is a female, there are some other factors that may inhibit the production of berries.
- Age: The age of the specimen may play a role; it takes some hollies three to five years to be able to produce berries.
- Planting Area: The conditions the specimen is in must be suitable to give plants the extra energy they need to produce berries. If you have planted your holly in a less than ideal environment it will become stressed and may be forced to spend resources on staying alive, not reproduction. Be sure to follow all growing advice regarding sun exposure, drainage levels, and protection from wind or cold.
- Weather: Speaking of the cold, weather can also play a role in reproduction. A late freeze in the spring after flowers have already bloomed can cause flowers to drop before berries are established.
- Lack of Pollinators: The weather and other factors can also negatively affect how many pollinators are in the area. With a low bee population, the pollen from the male plants may never make it to the female flowers.
Red Sprite Winterberry - Proximity to Males: It is important to make sure the holly is in proximity to a male that is compatible. Some hollies are quite picky about their Romeos take for example the famous Winterberry pair Jim Dandy and Red Sprite, and the Blue Holly lovers Blue Prince and Blue Princess. Others like American, Chinese, or Red Hybrid hollies are more right time – right place romantics, taking any male holly that flowers at the same time. Advice varies on the male to female ratio and distance between each, but generally one male can pollinate 5 – 10 females within a quarter mile radius.
If your holly is older, in the perfect location, has had plenty of bees around for the past few seasons and still isn’t producing berries, maybe your she-holly is a he-holly. The only way to easily identify the difference between a male a female holly is by identifying the flowers. Holly blooms often come and go unnoticed, so diligence and patience are required. Flowers arrive anytime from March – June depending on the variety and produce small white, cream, or light pink flowers. See below illustrations showing the difference between the male and female hollies.
Notice how the female hollies have an enlarged and rounded center, or pistil. The green pistil when fertilized will grow and turn into the bright red berries that brighten up our landscapes. On the male flowers you should see four or more stamen that have tips covered in yellow powder, which of course if the pollen! Female flowers are often singularly stemmed, while males tend to exist in larger clusters. Their sweet fragrance draws bees quickly and soon pollen will be travelling from plant to plant.
Now that you have the tools to ensure your hollies have berries come next winter, go out there a become a plant matchmaker!
