Ilex verticillata, berries, and the definition of a cultivar

Ilex verticillata 'Winter Red' (Winterberry)

This shrub should be quite a bit more recognizable, as it is quite common both in cultivation, as well as in the wild where it particularly stands out this time of year. Native to the wetlands of the Eastern and Central United States, as well as a similar range in Canada. It generally reaches 6-10' in height with a similar spread.

The characteristic berries actually appear in late summer, but persist well into winter. I'm not sure as to exactly how long the berries remain on the plants, but I've found birds generally pick these clean by the time the spring plants start putting on their show.

In terms of color, shape, and timing, some might pick up on these as looking similar to berries from the evergreen Holly Tree. The winterberry is actually in the same genus as hollies (Ilex) so obviously shares some of its characteristics. Primarily, the fact that these winterberries are dioecious, meaning each shrub is either male or female, but not both. Therefore, in order to get a fruit set at all, one needs to have both a male and at least one female plant (though generally most gardeners will have at least 3-4 females). The male plant will not produce berries, so the general convention is to hide the male behind the females.

Crushed winterberry. Note the multiple seeds

We've already covered drupes, so this seems like a logical place to mention another type of wet fruit, the berry.

Until I started paying attention to such things, I would generally refer to larger fruits such as oranges as "fruits", and smaller ones such as blueberries as "berries"

It's not the size of the fruit that botanists use to make this distinction, but the number of seeds it contains. Some of the largest fruits we see in the produce isle, such as the grapefruit (Citrus x paradisi) and watermelon (Citrullus lanatus), are defined as berries due to having multiple seeds, where even the smallest cherries are considered drupes due to having one solitary pitted seed.

So next time someone acts all smug by bringing up the fact that tomatoes are fruits and not vegetables, you can smile to yourself secure with the fact that you know more, as the tomato is a berry.


Alright, now for a bit of horticultural terminology: I threw around the term "cultivar" a few times in the entry on Prunus mume, which though second nature to those of us in the horticultural field, is not exactly standard vernacular. It's a fairly easy concept though. I'll walk you through it.

We've defined Winterberry above as a shrub possessing red berries. But say you have quite a few of these on your property, and one day as they all produce fruit, you discover a freak of nature which looks like this:

Ilex verticillata 'Winter Gold'

Plants, like any other form of life, have a certain amount of variability to them, be it leaf shape, flower size, resistance to a certain pest. or in this case, fruit color. As a result of sexual reproduction between two plants, a mutant occurred which has a dark yellow or golden berry as opposed to the traditional red.

Now being a plant enthusiast, this excites you and you can't wait to share your new plant with all your friends. You give them all a few of your prized golden berries and they begin growing new plants from their seeds. However, a few years later, when the offspring produces fruit of its own, only a scant few of them produce these golden berries, the majority of them reverting back to the standard red. And most disappointingly, about half didn't even produce berries at all.

So where did we go wrong? By choosing to hand out berries, and having our friends grow these plants from seed, we distributed plants which had our golden winterberry as the female parent but with an unspecified male. Sexual reproduction took place, so the seeds we handed out do not have identical DNA to our parent, golden-fruited plant. The 50% that didn't fruit are probably male offspring, and the female offspring which produced red berries likely did so as a result of genes from the male parent.

In order to distribute identical plants, we need to produce clones of our golden-fruited winterberry. For shrubs, this is typically done by taking cuttings. Tips of some of these branches would be removed, then the cut end dipped in a plant growth regulator such as Indoleacetic Acid (an Auxin). These cuttings are then stuck into a medium and kept in a high humidity environment, where the hormone will stimulate the cut ends of these twigs into producing roots. Usually 4-6 weeks later, the roots have grown to a significant enough size for the cuttings to be transplanted into a pot where they can continue to grow until big enough to be planted. If you give these to your friends, they'll all be female, and will all produce gold berries.

One step remains, we need a name for our plant, especially if we're proud enough of it we want to try to get local nurseries to distribute it further. In the case of this golden-fruited winterberry, the introducers chose the name "Winter Gold". The golden-fruited winterberry is a cultivar (which I believe to be shorthand for "cultivated variety"), and Winter Gold is the name of this cultivar. When using this as a part of the botanic name, Ilex verticillata, "Winter Gold" follows it in single quotes but not italicized, making the correct botanic name of this plant Ilex verticillata 'Winter Gold'
Another common (though now outdated) convention is to write the name as Ilex verticillata Cv. Winter Gold. You may see this occasionally on old botanic garden labels, or those produced with a label maker which cannot handle punctuation.

At the end of the day, I think I prefer the bright red of the straight species to the duller gold of this particular cultivar, but a little variety is always nice and a few plantings of these can help to break up the monotony where winterberry is used heavily.

Unlike Prunus mume, this plant is ubiquitous in cultivation, particularly in native-themed gardens, and a wide variety of cultivars are readily available in any nursery. The three I am most familar with are 'Winter Red' and 'Winter Gold', pictured above, and 'Red Sprite'. Winter Red and Gold are both taller forms of the species, reaching 7-9' at maturity whereas Red Sprite is smaller, reaching only 3-5'. Most Ilex species can tolerate fairly heavy pruning however, so it should be fairly easy to keep this plant to an appropriate size without fear of harming it too much. Note that for fruiting though, you will still need a male plant, of which a few cultivars exist. 'Southern Gentleman' is typically sold as a pollinator for the taller cultivars, whereas 'Jim Dandy' is more similar in height to 'Red Sprite' and the smaller cultivars, so often sold alongside them.

First snow of the year today here in Delaware, though it's predicted to soon turn to freezing rain. Might be able to get a few neat photos of these winter-interest plants with snow as a backdrop while doing some work for the botanic garden tomorrow.