Getting More Berries on Winterberry
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Q. Ken in Sellersville, PA (home of the esteemed Sellersville Theatre, where I recently saw the Harry James Orchestra) tersely writes: "could you please tell me the best time of year to prune my winterberry bushes?"
A. In response I asked Ken two questions. 1) Does your email charge you by the word? And 2) Why do you think they need to be pruned?
Q. Ken wisely ignored question #1 and responds: "They're on either side of my entrance gate and have gotten a bit too large. They also bloom beautifully in the spring but fail to produce many berries. I thought pruning might put a bit more energy into the fewer berries."
A. As my late father, a Philadelphia Police Homicide Detective, once taught me: "keep the suspect talking long enough and you'll figure out what's really going on". Great example here, as the actual problem is only related in the follow up email—although the subjects of pruning and fruiting ARE related.
Winterberry (also known as Coralberry and Black Alder) is a native American holly—and, come to think of it, a native Canadian holly as well, as its range extends North into Newfoundland and Ontario (then down the coast West to Tennessee and South to Alabama). It's deciduous—it loses its leaves in the winter—but is still a full-fledged cold-weather ornamental as it often produces so many bright red berries that you can't see the branches underneath.
Unless you are Ken, of course.
Luckily his solution is easy; he just needs another man around the house; specifically, a male holly. Like almost all members of the Ilex genus, Winterberry requires a male pollinator somewhat nearby to produce lots of berries. But not just any male holly—Winterberry's consort must be a gent with good timing as well, as both male and female plants need to be in bloom at the same time.
And to somewhat complicate the matter, there are many different 'named varieties' of Winterberry (including Afterglow, Berry Heavy, Berry Nice, Red Sprite, Sparkleberry and Winter Red); and they bloom at different times. Some flower early in the Spring, while others don't flower heavily until mid-June. To get barrels of berries, you need a male plant in the neighborhood whose bloom time overlaps that of your females as much as possible.
I say 'in the neighborhood' because I have a 'blue holly' that is covered in berries most years without my personally ever having secured a boyfriend for her—or even spotting the cad responsible in the neighborhood. But the berries are proof that the right kind of guy is somewhere in the area. Bees are known to carry the pollen quite a distance, so the male pollinator plant doesn't have to be right next to the female plants in question. And that's a good thing—since males don't produce berries, they're not very showy in the winter and good candidates to tuck into out of the way places.
Now—if you saved the plant tag or recognized one of those variety names you should be able to find the perfect pollinator; the Internet is filled with charts of perfect matches. But you can also observe when your girls' flowers open and then make an educated guess.
If they flower in May, you want one of the 'early males' like "Jim Dandy" (love that name). If they wait until the middle of June, you want a 'late male' like "Southern Gentleman". And you have a good amount of wiggle room, as both males and females flower for about three weeks, and many males overlap a good number of female varieties.
But horticulturists still stress that getting an exact match will produce the most berries. That's why some males share a similar variety name of their spouse-to-be, like the "Blue Prince" that's recommended for my "Blue Princess" (who is not 'blue' because she does have a guy somewhere nearby).
So pruning will not produce more berries; just the opposite. Pruning now would remove the buds that would have otherwise flowered in May and/or June. Then it doesn't matter how many men come calling.
If you can discern the variety name, be ready to provide the perfect paramour this spring. Get one that's already a good size, leave it in its pot and put it close by your ladies (one male can pollinate half a dozen female plants) for the best first-season results. Then you can plant it someplace else close-by but out-of-the-way once the berries start to appear on your girls.
At that point you can do some gentle pruning if the plants are getting in the way. Otherwise, be patient until next winter, when you can selectively prune entire branches for home-made wreaths and swags during the holidays. (Do this during the first extended cold spell when the leaves are gone and the plants are dormant.) But don't be too aggressive, as the berries are a favorite late-winter treat for robins. If you wake up one morning and most of your berries are suddenly gone, you'll know that Spring can't be far away.
One other thought: Winterberry hollies like a wet soil but don't require it (all plants with waxy leaves hold their water well); and some sources suggest that the plants tend to spread out "into a thicket" in really wet soil but stay nice and tight when the soil is on the dry side. So if your plants are just a bit unkempt as opposed to overgrown, try to cut back on any extra watering in that area.