treesexism

The Horticulturalist Whose Life’s Work Is to End ‘Botanical Sexism’

A day with the man who believes allergies are the result of 75 years of exclusively planting all-male trees in urban landscapes

“I’d say you’re the first reporter who’s ever been offered a ride in my truck,” says Tom Ogren, a 72-year-old Dude-like horticulturist driving a 1999 charcoal gray Mazda B2500 pickup whose odometer tops 270,000 miles, within minutes of our journey through San Luis Obispo, California. My feet awkwardly rest on a pile of nomadic necessities scattered on the passenger side floor — duct tape; a jug of water; a 15-pound dumbbell; a small plant clipper; a smattering of different sized screwdrivers, pliers and Channellocks; instant tire inflator; a knife sharpener; bungee cords, etc. A quick glance at the cargo bed reveals more of the same: adjustable straps for a kayak; solar lanterns; sleeping pads; camp chairs; rock hammers; sledges; chisels; fishing tackle; canned food; and a bottle of brown booze.

“I’m often in places where there’s no one else around, and I need to be able to adapt and improvise as I go along,” Ogren explains, figuring he’s slept in the truck more than a thousand nights, many of which occurred during a coast-to-coast allergy audit of the 11 largest cities in Canada, sponsored by Johnson & Johnson. In each, he studied the urban landscapes and visited local nurseries to see exactly which plants were being sold and how allergy-friendly they were (and weren’t).

Ogren is an allergy expert and patriarch of the allergy-free gardening movement. His first book, Safe Sex in the Garden, introduced a groundbreaking theory: Single-sex male trees and shrubs were making us sick. Plants, trees and shrubs do, in fact, have a gender. Most are monoecious, meaning they have male and female flowers. For example, hazelnut, apple and most citrus trees produce “perfect” flowers containing male and female parts within a single blossom. But a few — like gingko, mulberry and ash trees — are dioecious, meaning each is distinctly female or male. Ogren says the latter are the problem. He argues that while males don’t litter the ground with seeds, fruits or pods, they do emit high quantities of pollen into the air and up our noses.

“If youre not an expert, as most people arent, just look for the berries, though it depends on the species,” Ogren explains. “For example, if its a holly and it has red berries, its a female, even if theres only one red berry on the whole bush. If you have a holly and it never makes any berries, its almost certainly a male. Likewise, if you have a juniper bush and it makes little juniper berries, then its female. If it never makes a berry, its male.”

Although Ogren never finished high school, he did earn a master’s degree in agriculture and horticulture from California Polytechnic State University. That said, most of his expertise in recognizing allergic plantlife has come working in the field (literally): He’s been a lemon picker in Santa Barbara; a dairy farmer in Minnesota; a brakeman on the Santa Fe Railroad; and a landscaper in a prison, which is actually where a lightbulb went off. He was newly married to his wife, Yvonne, who was suffering from allergies and asthma. Attempting to educate himself on her plight, he began reading a book by a psychologist who believed allergies, which tend to hit women hardest, to be psychosomatic. Ogren thought so too and was quite unsympathetic; he still, though, continued to study the connection between plants and allergies.

“I was on a prison landscaping job, and there were lots of acacia trees around,” he recalls. “I noticed my workers sniffling and sneezing a lot, and suddenly, I realized how wrong I’d been.” His exact realization: That the plants producing the most allergy-triggering pollen were male and that most municipal plantings were using just male plants to mitigate the droppings. Further research led to him patenting the Ogren Plant Allergy Scale (OPALS), a first-of-its-kind reference guide of the allergy levels of more than 3,000 common trees, shrubs, flowers and grasses.

Today, in Ogren’s pickup, we’re on the lookout for “tree semen” (i.e., pollen), an overabundance of which he believes has resulted from 75 years of exclusively planting all-male trees in urban landscapes. (In some cities he’s studied, male trees make up more than 80 percent of all those planted.) Along with climate change, Ogren says this phenomenon — which he refers to as “botanical sexism” — is the reason why allergies have gotten so bad.

It wasn’t always this way. Before 1950, most of the trees in the U.S. urban forest were grown from seedlings and evenly split among genders. That all began to change in 1949, Ogren says, when the USDA Yearbook of Agriculture offered the following advice: “When used for street plantings, only male trees should be selected to avoid the nuisance from the seed.”

He claims the epidemic of allergies started shortly thereafter. The numbers more or less back him up. That is, while in 1952 only two percent of the U.S. population had allergies, 30 percent of adults and 40 percent of children now have some form of allergic reaction to pollen. “We’ve got a serious problem, and it’s getting worse,” Ogren says. Male trees spew their gametes in every direction indiscriminately, he adds, which is all well and good in the wild, where female trees soak up pollen, but as urban forestry is now dominated by male trees, city-dwellers are being drenched in tree spunk. Among the worst, he says, is the ginkgo tree. “Take some ginkgo pollen, add a little warm water and check it out under a microscope,” he suggests. “It looks just like bull semen!” Worse yet, he continues, “Once the pollen gets in your nose, it will germinate and start swimming up there to get to where it’s going.”

“That’s implausible,” counters Sheila McCormick, a professor emerita in pollen and plant fertilization at the University of California, Berkeley, who laughs off Ogren’s contention. (A 2006 paper from the National Institutes of Health, however, found that, indeed, ginkgo biloba “are the only seed plants with motile sperm cells” — while human sperm each have a single tail, or flagellum, gingko sperm have around a thousand.)

But back to the inequality of it all: “This is just like typical sexism,” Ogren says, pointing to a row of identical cloned cypress trees lining a sleepy San Luis Obispo cul-de-sac. “It’s the old boys club: Males are preferred, and females are considered to be shit. Despite there being thousands of trees they could have used, all we see now are the same male clones.”

Ogren’s hypothesis is echoed by Ravishankar Palanivelu, associate professor of plant science at the University of Arizona. “People trying to solve a problem [all-male plants are ‘litter-free’ because they shed no messy seeds, fruits or pods] inadvertently created another one — having too much pollen in the air, leading to many intangibles relating to people’s exposure to excess pollen,” he explains.

“There’s no quackery associated with that,” agrees David Neale, a professor of plant sciences at the University of California, Davis, who confirms that there’s a widely understood strategy of planting male-only trees to mitigate the nuisance of female droppings. “Planting these male-specific pollen producing trees in abundance in the urban environment is just adding to the problem. It’s not the sole source of pollen, but it certainly has contributed.”

In Ogren’s truck, a pair of well-defined biceps peek through the sleeves of a T-shirt reading “Beers Not Bombs,” as Ogren points to a row of xylosma hedges in front of a home, all of which he says are male and highly allergenic. The biceps are evidence of a 20-plus year career as a boxer. Ogren ran away from home when he was 15 and joined a traveling carnival, where he immediately strapped on a pair of gloves and hopped in the ring. If he stayed in for three rounds, he’d typically win $25 or $50. Meanwhile, the guys from the carnival would go around and place bets with the locals. “If a mark wasn’t very tough, we’d lose the second round on purpose to get more bets down. My folks didn’t know where I was for a long time until the cops grabbed me,” he says with a sigh, before pointing to four more male ash trees alongside a house. “There are 9,000 ash trees in San Luis Obispo and only six or seven are female,” he says. “One of which is in my collection.”

Ogren — who calls himself a “botanical feminist” — cultivates trees from cuttings taken from the female branches of monoecious trees (again, those bearing both male and female flowers) in his backyard as a chivalric gesture for Yvonne, re-landscaping their home to remove any plants that might trigger her allergies. “This tree alone will produce over a billion grains of pollen,” he says of a giant male oak in front of an elementary school. “But there are no females to pick it up. So where’s it gonna go? In our noses and in our eyes, that’s where.”

Next to it, stand a pair of male Chinese Elm trees. “In the fall, those will make kids sick. A lot of the most allergenic landscapes I find are at schoolyards,” he explains. “I imagine the natural testosterones in pollen makes the boys so horny that it’s hard for them to concentrate on school, while large doses of it could even lead to things like road rage.”  

My eyebrows sufficiently raised, I turn to Theodore C. Friedman, an endocrinologist in L.A., to see if inhaling natural testosterone could actually have such an effect on humans. While he can’t speak to the horny schoolboy claim, aggressive behavior like road rage is “possible,” he says, adding that for women, it could lead to extra hair growth, acne and infertility, and in children, it could result in starting puberty earlier and a shorter stature. And he does think environmental factors are affecting men’s lower testosterone levels and sperm counts, both of which have declined over the last 40 years. “Something in the environment is causing this, but nobody seems to know what that is. Yes, it could be related to pollen, but it also could be a host of other things — like pesticides.”

Others are far more skeptical. “Ogren’s theories aren’t scientifically sound in any way,” counters Matt Ritter, a botany professor at California Polytechnic State University and author of California Plants: A Guide to Our Iconic Flora. “For one thing, all xylosma trees in California, and the world, are female and male, so I have no idea what Tom’s talking about. He comes up with this idea, writes a book about it and it’s scaring people who don’t know what he’s talking about. It doesn’t make any sense because it’s not scientifically proven. It’s based in fear, which takes you a long way in the world. Just look at Trump.” (“100 percent wrong,” Ogren rebuts. “All of the xylosma in California are clonal males, with the exception of a few I have in my own yard that are fruit-producing female plants.”)

Ritter’s not the only plant scholar poking holes in Ogren’s misogynistic botany claims. “Mr. Ogren’s theory is unfounded, purely because there are no numbers to support this idea that male cultivars dominate the landscape,” says Sean Halloran, plant propagator at The Arnold Arboretum of Harvard University, adding that numbers and data analysis are what matters, not what we believe to be true. “Confirmation bias lets you see what you want to see. It’s possible that in one small area of an urban park, Ogren is correct. But when you look at the industry as a whole, I very much doubt this idea has legs.”

Nonetheless, Ogren’s mission continues. Urban foresters in San Luis Obispo have recently contracted him to design the landscaping for a new housing project, the San Luis Ranch, which is presently an open field extending as far as the eye can see. Soon, however, it will have 580 new homes, a hotel and a commercial area. “The whole thing is going to be done according to OPALS,” he says, barely able to contain his excitement. That’s because it will be the first-of-its kind, entirely non-allergenic landscape in the U.S. with zero male-only clonal plants and trees, which he believes should be replicated nationwide.

The biggest challenge to this effort, he says, will come from Big Nursery, the $41 billion garden store industry. Ogren wants them to follow the lead of Nigel Clarke, owner of Queux Plant Centre on the island of Guernsey in the English Channel, who labels every plant he sells with an OPALS number. “By doing this, I’m not adding to the stigma already experienced by allergy suffers, and I’m showing them that I genuinely care,” Clarke tells me, adding that his business has significantly increased since he began the OPALS labeling and that doctors have begun recommending that their patients shop there. “But as I’ve been the first in the world to do it, there’s a long way to go.”

Ogren’s been knocking on the door of U.S. nurseries for years, offering to develop a line of female, allergy-free trees and shrubs. “If I buy a can of beans and have high blood blood pressure, I wanna know if it’s loaded with sodium. Why should plants be any different?” But he believes Big Nursery continues to thwart his efforts. “Some of that crap you bring home could cause problems for you and your family for years,” he warns. “It may even cause problems for your dog. But they don’t want that idea to get into the public and think of me as the enemy who’s trying to destroy the horticulture trade. They won’t even return my calls.”

Nevertheless, the botanical feminist persists.