Did You Know? Hollies are Dioecious

 

Yep, it’s true. Hollies are one of the plants that have to have a male and female to produce berries. They’ll each flower separately but if there’s not a man around, girlfriend’s not producing any fruit. And many hollies are grown for their beautiful red berries that are borne in the fall and persist until winter when they are picked clean by the birds.

Let’s discuss the sexuality of the Ilex genus a bit further to fully understand what requirements hollies have for pollination. Hollies are considered dioecious which means that male flowers are produced on one plant and female flowers are produced on another. Whether it be through the wind or by insects, the pollen from the male flower must make it to the female plant’s stigma for pollination to occur. When the flower is pollinated, a berry is produced as the result.

Some people wonder if a native American holly (Ilex opaca) can pollinate the other hollies in their yard and the general answer is no. Mother Nature knew better than to let that happen; otherwise we would have a jumble of hollies that had crossed with each other and no individual species. There are some species that can be pollinated by Ilex opaca and they include Ilex attenuata and Ilex aquifolium. In the nursery trade, male and female hollies are labeled and sold as such. For instance, Ilex x meservae ‘China Girl’ is pollinated by ‘China Boy’. And Ilex verticillata ‘Apollo’ pollinates Ilex verticillata ‘Red Sprite’. With all of that being said, there are some exceptions to the rules and they include the ever popular Ilex x ‘Nellie R. Stevens’. Nellie, as she is lovingly referred to, is partially parthenocarpic which means that she is self-pollinating but the fruits she produces are sterile. Even with that, she will produce better fruit set if an Ilex x ‘Edward J. Stevens’ is close by.

So how close do your hollies need to be to each other for good fruit set?

In the case of Ilex opaca, a quarter of a mile will suffice for high quality fruit set. In the case of Ilex verticillata, you’ll need one male for every 5-6 females. As you can see in the picture to the left, it’s best to plant your males in the back where there fruitless stems won’t be so apparent.

I hope that you’ve learned a bit about holly berry production today. If you have any experience with your hollies having exceptional fruit production or very poor production, leave me a comment below or e-mail me at stacey@midatlanticgardening.com. Happy gardening!

December 19, 2011Permalink Leave a comment

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