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Question of the Week © 2017 Mike McGrath
Note: Hundreds of Mike's informative articles are available (in alphabetical order!) right here at the Gardens Alive website. To find Mike's answers to your specific garden problem, Click here and find your topic (like Weeds, Worms, Rhododendrons...) in our complete alphabetical archive of Questions of the Week.
The Problem with Paw-Paws
Q. I have two pawpaw trees planted about ten feet apart (I think the varieties are 'Wells' and 'Sunflower'). They're around five years old and growing well. For the past two springs, they've set blossoms nicely, raising my hopes of getting my first crop of fruit, but within a few days, the flowers all dropped and no fruit developed. Not one. The trees appear very healthy otherwise. What could be wrong? I remember you fondly from your Organic Gardening days and appreciate your guidance!
--- Ron in Cold Spring, New York
A. Ah yes; it was a genuine privilege to serve as editor of 'OG' back in the 1990s; those were the days….Oh well, out of La-La-Land and back to Ron's lack of pawpaw land.
For those of you who follow these adventures on a regular basis, it will be no surprise that, yes—I did ask for help from our resident fruit growing expert Lee Reich, author of numerous excellent books on pruning and backyard fruit growing.
I also went back and re-read sections of Andrew Moore's great 2015 book on the famed 'banana of the North': "Pawpaw—in search of America's Forgotten Fruit". We had Andrew on the show shortly after the book came out and it was a great interview. But let's start with Lee Reich. His thoughts:
Lee: "The most obvious possibility is that Ron does not actually have two different varieties. His plants may have been mislabeled at the nursery, which is more common than you might think—and two different varieties are needed for successful pollination." But Lee adds that he has twenty trees that definitely include a good number of different varieties and his have also borne very little to no fruit for the past two years.
Which he attributes to…?
He wavers. First, he speculates that the failure two years ago was due to that late and severe Spring frost that nailed so many plants in the mid-Atlantic—in my case (and in many other cases) hydrangeas and peaches especially. But he then acknowledges "that this past spring's weather was perfect for fruit set in virtually all fruits."
So—no sudden freeze to damage the flowers. And it's hard to imagine a lack of pollinators at Lee's place; he probably has as many native bees in residence as I do. Ah, but bees and other pretty things like butterflies don't pollinate pawpaws. As Lee notes, pawpaws are pollinated by flies and beetles—so he says that next spring, he's going to hand-pollinate some trees "in an attempt to verify whether pollen not being transferred is the problem."
Flies? And beetles?
Yes. Like the famed 'corpse flower' that put on a magnificent show at the National Arboretum last month (August of 2017 if you're taking notes), pawpaw flowers smell like rotting flesh. And so insects that take care of things like roadkill are attracted to the plants and go from flower to flower, just like bees do with flowers that smell nice. Or at least that don't smell like rotting flesh. Ahem.
So we suggest that Mark also hand-pollinate his flowers. Or turn to the trick that pawpaw author Andrew Moore explains many growers rely on: Drag some roadkill under the plants or dress the branches with chicken skins. That'll bring in the flies!
Oh dear; there goes our last Vegan follower. Let's discuss some less charming thoughts, shall we? Like location. In his fine book, Andrew Moore goes into great detail about the pawpaw's native range, which includes all of Ohio, Kentucky, Indiana and Virginia South to where winters start to get too warm for the trees to get enough 'chilling hours'—plus up North to roughly the Southern half of Pennsylvania and even a little bit of Southern Michigan….
But not even the tiniest sliver of New York state….
Now, New York stater Lee says that he has gotten fruit in the past, and he's much further North than Mark—who, ideally (Mark, that is), is located just across the Hudson from West Point; and pawpaws are known as a 'river fruit'. So his location is technically twice better than Lee's—its less cold in winter and right on the water.
And, if they were correctly named, the varieties he's growing are ideal. "Wells" won a famous taste test conducted at Kentucky State University (and popularized in the pages of Organic Gardening magazine decades before I was the editor). And Andrew Moore describes "Sunflower" as "a favorite among growers" and speculates—like Lee—that it may even be self-fruitful (needing no other-variety pollinator).
So theoretically, both these guys should be eating pawpaws right now.
Like many experienced gardeners, Lee has learned that some things just defy explanation. As he explained in his email: "I'm not sure why I would have a lack of pollinating insects, but gardens are complex biological systems" that can always surprise us.
Small comfort to Mark?
Not at all. Despite his being outside the dedicated native range, I like his location. And his trees flower. So I suggest he plant a third named variety just in case Lee's labeling suspicions are correct, be prepared to protect the flowers if temps drop sharply while they're open, and…
Voice of reason: And what?! Two weeks ago, it was snakes and rats! And now we're telling people to hang festive chicken skins in their orchards?!
Mike: I was going to conclude with "and gently transfer pollen from flower to flower with an artist's paintbrush…"
VOR: You were not!
Mike: Was too.
VOR: Were not!
Mike: Was too….