My Epigenetic Epiphany and the Gingko Hermaphrodite



High up in a white pine last summer, on our farm in Salvisa, Kentucky, I spotted something odd. I called my neighbor Otis Knox and asked him if he’d ever seen a Witches’ Broom. He came down to investigate.

 Bill Barnes with the wonderful and capable interns of the Morris Arboretum and their completed grafts of Pinus strobus 'Otis Knox'
Bill Barnes with the wonderful and capable interns of the Morris Arboretum and their completed grafts of Pinus strobus ‘Otis Knox’

I pointed toward the 30” diameter growth. Otis said he had seen Witches’ Broom before, but hadn’t known that’s what they were called. He had not seen this one.

Witches’ Broom is caused by a peculiar, and not fully understood, epigenetic gene expression that goes haywire in trees and occasionally in shrubs. A switch on a gene, ordinarily turned off, is turned on. Or vice versa. The DNA is the same as that of the parent, but an abnormal growth occurs on a portion of the plant due either to a fungus, bacteria, virus, stress hormones or possibly mitochondrial mischief.

Witches' broom in white pine
Witches’ Broom in white pine

Holly Cooper, my sister-in-law, was the first to notice the white pine Witches’ Broom. I’d walked past it hundreds of times and not noticed a thing.

Holly is not named Holly for nothing. She’s a great gardener and photographer. Her grandfather, Theodore Klein, was a legendary plant collector and Kentucky nurseryman. Mr. Klein had a fondness for hollies, hence Holly’s name. Yew Dell, his home, nursery and garden, in Crestwood, Kentucky, has a beautiful holly allée. Yew Dell Botanical Gardens, since Mr. Klein’s death in 1998, has become a popular public garden.

Otis Knox had brought young white pine, Pinus strobus, seedlings from the mountains of Wolfe County, Kentucky, and planted a sweeping curve of them along our gravel drive in 1976, at what was then his new Salvisa home. The property has changed hands several times since, but Otis didn’t move far away. He lives on a farm across the Salt River from his old home place.

Otis Knox and his white pines
Otis Knox and his white pines

My arborist friend Robert Rollins gathered scion wood from the Witches’ Broom in late January with a long pole pruner. These pieces were sent the next day to two growers to be grafted onto white pine seedling understock.

Robert Rollins holding witches' broom
Robert Rollins holding Witches’ Broom

“Witches’ Broom,” according to Sidney Waxman, in the 1983 Proceedings of the International Plant Propagators Society, “… are dense shrub-like growths that occur as a result of the mutation of buds. They are found mainly on conifers and generally retain their dwarf and dense character when propagated vegetatively.” Witches’ Brooms have been grafted onto seedling understock since 1874, according to Waxman. Over 20,000 seedlings of pines (including white pine), Norway spruce, Larix laricina and Canadian hemlock were grown at the University of Connecticut between 1964 and 1983.

I named the clone in honor of my Salvisa neighbor, but don’t expect to see ‘Otis Knox’ in a glittery rollout, with a brand-marketing program, anytime soon. The beach-ball-sized white pine mutant needs a few more years in Santa’s workshop before it, or its progeny, are unwrapped.

Bill Barnes, and interns from the Morris Arboretum, have grafted a few of these pines. So has Karl Klein, the uncle of Holly Cooper and the son of Theodore Klein of Yew Dell.

Karl Klein with finished graft of 'Otis Knox'
Karl Klein with finished graft of ‘Otis Knox’

According to Bill Barnes, a Pennsylvania nurseryman, the grafted Witches’ Broom may not amount to much. The modified plants don’t always behave as they did when they clung to mama. The real action, he says, may come in the next generation. And though white pine Witches’ Broom are a dime a dozen, it will be interesting to watch what happens from the progeny of ‘Otis Knox’.

I could see, from the cut pieces of scion wood, that the remaining Witches’ Broom, hanging in the pine, will be flowering this spring.  Let me do the math…. That certainly means that pinecones could be produced in two years. Seedlings could be underway in three years.  It might take a few more years to see what becomes of the offspring of the Witches’ Broom. They might all die immediately, or they could produce perfectly normal trees. Or there’s the slim chance a few might resemble, well, who knows what?

There’s nothing wrong with normal, of course, but it’s the peculiar outliers that get gardeners’ tongues wagging.

Gingko at Cave Hill Cemetery
Gingko at Cave Hill Cemetery

There’s a fascinating Witches’ Broom in a huge and spectacular Gingko at Cave Hill Cemetery in Louisville, 63 miles from Salvisa. The male tree was barren and produced no seeds. The tree, planted in the mid 19th century, suddenly produced a peculiar, stubby growth, high in its branches, late in the 20th century.

And guess what: The Witches’ Broom was a seed-producing female.

The once male Gingko is now a gender-bending, street-legal hermaphrodite.


    • Love this article, and indeed the explanation of “witches’ brooms” is the answer to a long overdue and forgotten websearch I meant to undertake.

      This Pagan Witch loves the idea–although most of our ritual broom have broomcorn bristles. I have no idea if they would make long-lived besoms or not, but a pine whose witches’ broom needles were of sufficient length to make a basket would be in demand in our communities, ore at least by the makers of besoms.

  1. Thanks for posting this! Every day I drive by a tree with a Witches’ Broom in it–now I know what to call it. I’ve been wondering for months what it is, thinking some huge bird built a nest or a bunch of branches fell into the same spot in the tree and so on. Now I know!

      • It’s in a very large Lodgepole pine, growing in the middle of a dense grove of Douglas fir, at about 500 feet in elevation (to field Joe’s question about higher elevations and radiation exposure). The witches’ broom is way up in the tree, about 30 feet up, just sitting there all by itself. I bet the birds and squirrels love it.

        Actually, when I think about high elevation and radiation exposure and trees, I am reminded that in all parts of the world, there is usually a point above which trees don’t grow (the tree line). So I wonder if they grow high enough anywhere to be really exposed to much radiation–anyone know?

        • I used to work at a lab (as a computer geek, not a technician) which analyzed samples for pollution of all kinds, including radioactive. Living in Boulder, CO, I was told, exposed you to extra radiation about equal to one dental X-ray per year. This radiation has an effect, but it would be very, very small. Since witch’s brooms aren’t that common, I would think that many trees would have to be looked at to see an statistical variation. And since there are so many other variables associated with high altitude environments and adaptations, it would be a real feat to establish this with any degree of confidence. (For example, suppose the minor variations in species X which suited it better for colder average temps also made it more susceptible to witch’s broom? Nailing down the cause of a barely measurable difference in occurrences would be a challenge.)

  2. First of all, best rant title ever (not to mention excellent names for a pair of rock bands, which, of course I just did mention, which makes that preliminary phrase pretty silly, no?). Must remember we all speak a language in which one first cuts a tree down and then cuts it up. But I digress.
    I remember reading a lot of years ago that witch’s brooms occurred more at higher elevations, suggesting that greater exposure to natural radiation had something to do with the phenomenon, but a quick, half-hearted Google search produced no results to corroborate that. Is that a debunked notion, or maybe too simplistic and failing to take into account all of the other potential causes of atypical growth? Am I too eager to discover a unified theory of witch’s brooms? Does the fact that all witch’s brooms float prove that they all are indeed witch’s brooms? Has all of this research been swept under the rug?

    • Joe, I hadn’t thought that the title of this piece might be worth a band name or two!

      I dug only a little into the science of the Witches’ Broom. There is a lot more out there. I can’t imagine that any of the WB
      science is being covered-up.

  3. All of the red (I think) Maples on my property behave normally (growing tall, with six – 12 inches of new growth a year) except for one, which in the past 10 years since I’ve noticed, grows about an inch a year. Many large leaves are produced on tiny spurs coming from the trunk (which grows in diametre about half as much as a ‘normal’ maple would) and tiny (ie really short) branches. It’s about three feet tall now – trees that would have germinated at the same time are 15 – 20 feet tall.

    Do you think a similar thing is happening as what produces Witches’ Brooms?

    • Chris-PEC, Your description of your red maple makes it sound like it is a seedling variation, and not a Witches’ Broom. It might be something to keep an eye on. A Witches’ Broom would have growth, perhaps like you describe, but occurring on a plant that is, otherwise, normal.

  4. Forgot–I’m used to some fishes and amphibians who switch sex/gender, but not plants!

    Transsexual trees, quelle idée! Do they desire different pronouns to be used at any point in their life spans? Some members of the LGBTQIA (etc) communities, who feel that they don’t identify with either male or female might find this transformation interesting.

    • Since I usually refer to plants as “it” no matter what gender they express (if they even have a preference), they probably just write me off as hopelessly insensitive, or at best clueless.

      • Anyone else remember the days when, in response to a child referring to an adult woman as “she”, the child would be sternly told, ” “She” is the cat’s mother”? Pronouns have always been a bit of a minefield, including the royal “we”. Personally, I hope we never widely adopt a gender non-specific pronoun like “co”, as was proposed a few decades ago. I enjoy the awkward dances we do around the subject that tend to keep it in sharper focus.

  5. Is that a record Ginko? There’s a large one at the Crawford Museum in Devou Park, Covington, KY, that might have been sent by Thomas Jefferson, but I don’t think it’s as big as the one pictured.

    • Tom, Lee Squires, of Louisville’s Cave Hill Cemetery, said he thinks this is Kentucky’s biggest. I’ll check-out Covington’s Gingko later this year. Thanks for the lead.

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