Naturally Ilex species are dioecious. Dioecious means "two houses" in Latin to reflect the fact that Ilex has male or female flowers on separate plants. Only about 10% of plant species have this condition. Most plants have "perfect" flowers, or male and female parts on each flower. For the benefit of future generations of plants being more fit for their changing environment, plants usually have various mechanisms in place to avoid self-pollination. Dioecy is just one such manifestation. The number of variations on this theme are amazing and clever. Mother Nature is the master at improvisation! Look at the two photos below. The first one is of a female flower. These are easy to distinguish from the berry-like protuberance in the center of the flower. Male flowers lack this structure and have pollen-bearing anthers. The male flowers are so numerous and carry such a large pollen load, that blooming hollies are irresistible to bees. To get berries on your hollies, you must have a male holly that blooms at the same time as the females. As long as there is a male somewhere in the vicinity, bees will locate it and pollinate your female hollies. Bees are amazing!
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| Ilex female flowers Wikipedia |
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| Ilex male flowers Wikipedia |
Plant breeders have managed to cross several species to achieve various goals, such as greater cold tolerance, and fruit set. Some crosses resulted in female plants that can set fruit without a male holly. These crosses usually contain some Ilex cornuta, or Chinese Holly, since Chinese Holly exhibits a condition called parthenocarpy. Parthenocarpy is the ability of a female plant to form sterile fruit in the absence of a male. Several plants can do this. The trait of parthenocarpy was used to breed "seedless" citrus and other plants. To complicate matters, Ilex cornuta, and its hybrids, sometimes have perfect flowers on male plants, followed by red fruits. These fruits contain four apparently normal-looking carpels, which may-or-may-not be viable.
And then it becomes complicated! There is a group of hollies bred for size and color, referred to as "Red Hollies." They were developed by Mitch Magee's Evergreen Nursery in Poplarville, Mississippi. The name comes from the red tint on new growth. These are upright attractive plants with a strong pyramidal growth habit. This group includes Ilex 'Festive", Ilex 'Cardinal', Ilex 'Oak Leaf', Ilex 'Little Red', and Ilex 'Robin'. 'Oak Leaf' Red Holly has a confusing and complex breeding history. I was curious if parthenocarpy or plant sex through pollination was working to form berries. In an effort to understand the formation of fruit on the Oak Leaf Red Holly, I emailed several holly experts, and did some research. 'Oak Leaf' Red Holly has functional male and female flower parts, perfect flowers, so it can pollinate itself, so no parthenocarpy, just fertilization. The parent is an open-pollinated Mary Nell holly. Mary Nell is a three-way hybrid. Oak Leaf has an unknown male parent. Unlike normal dioecious hollies,‘Oak Leaf’ is not female but a hermaphrodite.
The Red Hollies, as a group, are a perplexing bunch of hybrids. All are claimed to be open-pollinated seedlings of 'Mary Nell', which is itself the result of controlled hybridization and is Ilex (cornuta 'Burfordii' × pernyi) 'Red Delight' × latifolia). You can imagine all of the male pollen flying around at a holly propagation grounds, and that is why the identity of the male pollinizer remains a mystery. Oakleaf holly ('Conaf') and its branch sport Oakland ('Magland') are variously listed on gardening websites as male, female, and both. The US Plant Patents on these cultivars says the flowers are "perfect", meaning having functional male and female parts. These plants do not have female flowers, as are present in most familiar hollies, (i.e. lacking a visible pistil), nor do they have male flowers (which lack functional pollen-bearing anthers). Rather, their flowers have small pistils surrounded by four pollen-bearing anthers. Botanically speaking, these would be considered androgynous, or hermaphroditic.
There is another Oak Leaf holly, Ilex 'Festive" ('Conaf'), which displays a different twist on plant sexuality. This plant appears to be andromonecious, that is, bearing both traditional male flowers, as well as occasional perfect flowers. It does not, however, seem to bear any female flowers. In each blooming season, the vast majority of the flowers are male, and appear to have moderate amounts of pollen. The perfect flowers tend to appear at the end of the blooming cycle, and produce misshapen, red fruits.
There is another Oak Leaf holly, Ilex 'Festive" ('Conaf'), which displays a different twist on plant sexuality. This plant appears to be andromonecious, that is, bearing both traditional male flowers, as well as occasional perfect flowers. It does not, however, seem to bear any female flowers. In each blooming season, the vast majority of the flowers are male, and appear to have moderate amounts of pollen. The perfect flowers tend to appear at the end of the blooming cycle, and produce misshapen, red fruits.
As for male pollenizers for Oakleaf holly, it seems that this plant does not produce a lot of fruit because of its complicated genetics. I communicated with Dr. James Resch, Ilex specialist, and he says even in nursery settings, where pollen from many species and hybrids is available, Oakleaf holly never seems to develop numerous fruits. It may be that the plant's complicated pedigree has created so many chromosomal mismatches, with would-be pollenizers, that effective pollination can only rarely happen.
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| Ilex aquifolium Wikipedia |
Two other super popular hollies are also the result of genetic crosses. They are gorgeous with their pyramidal habit, large and glossy foliage, and, of course, the beautiful berries. Both Ilex 'Mary Nell' and 'Nellie R. Stevens' have anthers that do not produce pollen, meaning that they do not have functional male flower parts. These two plants produce fruit through parthenocarpy and by being pollinated by a male I. cornuta or I. pernyi. A male selection suggested as a pollenizer is 'Edward J. Stevens'. 'Nellie R. Stevens' is the result of a cross between Ilex cornuta and Ilex aquifolium. Normally, Ilex aquifolium does not grow well in the heat and humidity of the South, but with the addition of Ilex cornuta genes, 'Nellie R. Stevens' is a long-standing staple in Southern gardens. 'Mary Nell' is a three-way cross with Ilex cornuta, Ilex pernyii, and Ilex latifolia. It is still helpful to have a male holly that blooms at the same time to increase fruit set. It is thought the almost ANY male holly that blooms at the same time will work, but I do not know this as a fact.
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| Nellie R. Stevens Hollie John Paul Endicott |
