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  • Writer's pictureBrooke Bowen

Spooky Forests, Tree Migrations, and Judi Dench the Dendrologist

Updated: Dec 2, 2020

“The trees have their requirements, with arboreal stoicism they edge toward the peaks, and from there they cannot levitate.”

"Nature is a Haunted House - but Art a House that tries to be haunted."


1. Plant Blindness

Part of this blog is an effort to encourage people to see plants in new ways, with the hope that an increase in knowledge fosters increased respect. One of the great things about this work is the growing community of people doing it. The In Defense of Plants podcast refers to the work as “curing plant-blindness”, in reference to a term coined in 1998 by Elisabeth Schussler and James Wandersee, a pair of US botanists and biology educators hoping to encourage more plant-focused discussion in introductory biology classrooms.

What do you see in this photo? Likely, you didn’t answer sausage tree. Photograph: Alamy Stock Photo

Plant blindness is “the inability to see or notice the plants in one’s own environment”. People, in general, have a tendency to ignore the plants in their lives. Humans are also prone to an “anthropocentric ranking of plants as inferior to animals and thus, as unworthy of consideration”, Schussler and Wansersee show.

When people are unable or uninterested in recognizing and identifying plants in their daily life, they are less likely to value them and less inclined to learn about them, and less likely to protect them.

According to a study by the Chicago Botanic Garden and the Botanic Gardens Conservation International, the number of undergraduate degrees in botany is rapidly declining. And even though 57% of endangered species in the US are plants, they only receive 4% of federal endangered species funding.

This human propensity to overlook the biological importance of plants in the natural word and in human affairs may have a huge impact on how we solve critical problems as a society. An article from The Conversation states the issue clearly. “Many of our biggest challenges of the 21st century are plant based: global warming, food security and the need for new pharmaceuticals that might help in the fight against diseases. Without a basic knowledge of plant structure, function and diversity, there’s little hope of addressing these problems.”


2. The Great Migration of Trees

When we think of migration, what comes to mind? Hooved animals kicking up dust as they cross hundreds of miles between the Serengeti and the Maasai Mara savannah each year. The epic journey of humpback whales swimming thousands of miles between Central American and Antarctica. Birds in flight overhead each changing season. Monarch Butterflies miraculously making their way to and from places they’ve never been.

It’s time we add a few members to the great migrators of the world. Sequoias, for one, migrate south when the weather gets too cold. Spruces resettle lands that have been recently-cleared. Trees are capable of migrating thousands of miles, sometimes up and over entire mountain ranges, and then back again. Many plant species are, in fact, on the move.

How can trees relocate?

Since we think of plants as sessile beings, fixed in one place, the image of traveling trees is hard to conjure. To better visualize what is going on in tree migration, there is an important distinction. The process of individuals moving away from their place of origin is known as dispersal. The process of entire populations moving to a new place is referred to as migration. Individual trees move only as seeds or spores. But a population, an entire forest, is a mobile organism. Author Zach St. George, in his new book The Journey of Trees, explains that “The migration of a forest is just many trees sprouting in the same direction.”

The speed at which forests move is excruciatingly slow. What we may witness in a human lifetime of a migrating forest is like seeing one flap of a migrating Monarch’s wings. Here’s how it works: The tree produces seeds and those seeds arrive in new places (via wind, water, or animal dispersal). Some of these seeds may land beyond the edges of its community’s current range, beyond the edges of the forest. If the place where the seed arrives is optimal for survival, and the tree grows, the forest edges have now shifted. If the forest shifts northward, for instance, it is because that direction offers a more optimal habitat than places in other directions, not because the forest only sent seeds north.

A Maple seed can travel hundreds of yards on the wind. Photo from Ohio State University

Why would a forest need to move?

This phenomenon has happened since the beginning of forests. St George writes, “Through the fossils that ancient forests left behind, scientists can track their movements over the eons. They shuffle back and forth across continents, sometimes following the same route more than once, like migrating birds of whales.” So what is the main driver behind the migration of trees? The ever-changing climate.

In a recent episode of the In Defense of Plants podcast, Angelica Patterson, a PhD student at Columbia University studying how climate change is affecting trees, explains that “The climate has been changing since the last ice age. The climate is always changing, but it’s the different rate of change that’s important. And we’re seeing this increased rate that is putting a lot of pressure on the natural ecosystems and the things that live within it.” After glaciers retreated across North America, trees moved in from the south, claiming the now optimal lands for their forests. This was a gradual change in climate, a pace the trees could match. The problem today is that climate change, the increasing global temperature, is happening too quickly for the trees to keep up.

Angelica Patterson studies how trees adapt to changing air temperatures. Photo from The Guardian

Which species are migrating?

Imagine visiting Saguaro National Park and seeing none of the cacti for which it is named. Think of what Joshua Tree National Park would be like without its iconic namesake. An increase in global temperature means many places are getting hotter and drier each year. These changes mean that many plant communities currently live on land that may not be able to sustain them in the near future. Some species, like certain oaks and maples, are heading west in response, where the weather is wetter. Some species might not have anywhere else to go.

Take the majestic sequoia (Sequoiadendron giganteum), for example, which thrives in only one place in the entire world, a limited area of the western Sierra Nevada mountains in California. St. George traveled with ecologist Nate Stephenson to Sequoia National Park, a place that St. George reveals may not hold Sequoias much longer. He explains that Sequoias were rare about 10,000 years ago, when the Sierra Nevada was warmer and dryer than it is today. “They huddled at the very edges of streams, teetering on the brink of extinction. Then, about forty-five hundred years ago, the Sierra Nevada grew a little cooler and wetter, and the trees spread out into their current distribution, reaching their modern abundance just two thousand years ago.” When California was hit with a major drought in 2013 & 2014, the sequoias started losing their leaves, an adaptation to restrict water loss. Stephenson and his cohorts were worried about what this meant for the future of the sequoia groves because no one had ever seen this happen before. When the heavy snows returned in 2017, the sequoias “flushed with new foliage” the following summer. This provided a mini preview of what might happen to the trees in a hotter, dryer future.

“Between 1985 and 2015 the average temperature in the sequoia groves of the southern Sierra Nevada increased by about four degrees Fahrenheit,” states St. George. There are no signs to indicate this increase will stop or reverse, so the sequoia will eventually need to find a new habitat with cooler temperatures and more water to survive as a species. The individuals will not all make it. When you remember that some Sequoia trees are over 3,500 years old, you start to grasp the great loss we face.

The famous General Sherman might need to be watered in the future to survive. Photo by Gabriela Quirós/KQED

What role should humans play in tree migration?

The eminent threat of lost forests has scientists all over the world working towards conservation of endangered species. St. George’s book explores the evolving movements of five tree species and reveals the ways that human actions have helped and hindered in their attempt to save the species they love. From his travels around the world to connect with ecologists, biologists, conservationists, and foresters, he exposes some of the stories of people moving trees. “These people”, he says, “have called what they’re doing by many different names: horticulture, forestry, ex situ conservation, assisted migration. Sometimes these actions seem likely to help either the tree or the people, but sometimes - as ever, when we use human hands to shape that which is not human - they seem just as likely to make things worse.”

Patterson urges for deep understanding before any action is taken. “Land changes all the time, land use changes all the time. Human responses depend on the goal and require an understanding of how plants work and what they need to optimally survive.”

One of St. George’s sources, Connie Barlow, admits that since she’s accepted the implications of climate change she’s accepted the end of civilization. She cheerfully says “I’m a collapsitarian”. Barlow is a fervent believer in assisted migration, a woman evangelically planting Florida Torreya pines up and down the east coast. It stands to reason that if you think the end of ordered life on earth is around the corner you’ll try anything to save it because it’s lost already. If you think the planet has a way of balancing itself out, that humanity is not lost, you may have a more measured approach. It depends on the perceived end and the amount of time left to carry methods out.

Each species and forest will need its own solution, and these solutions may be extremely sophisticated or as easy as walking away. But all will require a deep understanding of the full ecosystem in which the trees currently live and the one to which they might move. Good science takes time, something we’re running out of.

The debate on assisted migration is far from over. And the variations of this method should be considered. Two interesting concepts I’d like to further explore were introduced to me in St. George’s book. One is the method of “assisted population migration”, in which humans plant seeds from a southern population of trees farther north but still within the species’ current range. The other is “assisted range expansion”, where seeds are planted outside a species’ current range. There is no one clear path forward, as the public discourse continues to show. Each species and forest will need its own solution, and these solutions may be extremely sophisticated or as easy as walking away. But all will require a deep understanding of the full ecosystem in which the trees currently live and the one to which they might move. Good science takes time, something we’re running out of.

What does the future hold?

With all of the pressing peril, what St. George’s book reveals is a relatively optimistic vision of the future, spurred on by a determined and hopefully array of humans focused on saving what they can.

In an interview with NPR, he lays it out. “Climate change is going to have these really dramatic effects on forests, we’re going to lose a lot of forests, we’re going to see species rearranged, we’ll probably see more fires and droughts and millions of dead trees.” Grim start, I know.

Photo of Zach St. George, via Twitter

But he goes on to say that “The book is very much about trees but it’s also very much about people, and I met a lot of people in the process who sort of see these changes coming and have mourned what has been lost and what will be lost and are still continuing to try and do good and try and work towards a better future. You can see these vast changes in the future and you can be worried about them but you can still continue to do good and work in the moment for small things.”


3. Judi Dench, Dendrologist in the making

“My life is just trees now, trees and champagne.”

- Dame Judi Dench in her 2017 BBC Documentary My Passion for Trees.

What a role model. What a charming human jewel who’s given us a heartfelt biology lesson while also introducing us to some of the coolest technology being used in tree research today.

Judi Dench listening to sounds of water movement beneath the bark, Still image from the documentary

This documentary is pure delight. Dench performs Shakespearean sonnets and then crawls right inside of a 1500 year old Yew trunk. She talks of pollen clouds so dense they’re mistaken for forest fires and she explains that her backyard is full of trees planted for loved-ones lost. “It is about remembering, and for me it’s something that’s living, that goes on… and the memory gets more wonderful.”

With the help of some super cool 3D imaging, Dench discovers that her favorite backyard oak is 200 years old, has 12 kilometers worth of branches and is currently storing about 25 tons of carbon. The videography is impressive, especially the shots of fungal threads in action and the hair ice that follows decomposition.

Judi Dench with rare Red Squirrel, Still image from documentary

Genuine amazement mixes with humor throughout. “I shall give up acting and lecture on trees I suspect, quite soon, probably...” Dench says laughing. There are also plenty of knowledge nuggets throughout. Thank you Judi Dench, for providing me with a beautifully simple explanation of how a pine cone forms.

The documentary is a journey of trees through the seasons, with the company of someone in awe of the forests that surround her. “I shall never be able to walk so nonchalantly through a woodland ever again, without thinking about what incredible work is going on under here.”


4. In Honor of Halloween Part 1: Massive Cucurbits

What does it take to make a 2,000 pound pumpkin?

Giant gourds on display at the New York Botanical Garden, Photo from NYBG/Marlon Co Photography

Each October, the New York Botanical Garden hosts a Giant Pumpkin Weekend, where they unveil some of the largest pumpkins in the world - pumpkins weighing in at over 2,000 pounds!

To grow a pumpkin the size of a small car is not an easy feat. It takes commitment, community and a ton of time and money. And not surprisingly, it starts with a seed.

According to a 2015 article in the Seattle times, about 30,000 people grow giant fruits and vegetables competitively, and pumpkins are the most popular produce. In 2012, a country club manager from Rhode Island grew a 2,009 pound pumpkin, barreling through the 1-ton barrier. Since then, seeds from Ron Wallace’s record-breaking gourd have sold for more than $1,000 each.

The value of these seeds derives not only from what they can produce, but how they themselves came to be. “Like most serious growers, Wallace ties plants’ blossoms closed and hand-pollinates them so he can be sure of the mother (the seed) and the father (the pollinator) and protect them from bees carrying pollen from a neighbor’s squash.” The top priority is ipholding the lineage of these massive fruits.

The Half Moon Bay Art and Pumpkin Festival, Photo courtesy of CBSSacramento

The pumpkins grown for size are not the same variety as those we use for jack-o-lanterns and pies. Dill’s Atlantic Giant variety of Cucurbita maxima seeds are the favorite among competitive growers. As these plants grow, the pumpkins can put on up to 45 pounds per day, mostly from water. They add flesh by transporting large amounts of sugar to their fruit, often a couple of pounds a day. This is done by creating more phloem, a complex plant tissue that helps to store and transport nutrients. The pumpkin’s physiology is a large part of the process.

Another large part of the process is human labor. Wallace spends up to 40 hours a week tending to his pastime. He explains that competitive produce growing is not for the casual hobbyist, “For growers who are competitive, it’s year-round. They’re studying, they’re researching, they’re building greenhouses, they’re looking at genetics… Most competitive giant pumpkin growers aren’t taking summer vacations.”

They aren’t doing it for the money either. Most competitive growers rarely make money or even break even. There are a few growers who get both the glory and the gravy. In 2018, a man from New Hampshire won $6,000 at a local fair for his 2,528 pound pumpkin. Another couple from California won over $14,000 for their 2,036 pound champion.

Tim Parks, of the Ohio Valley growers club, harvests his 2010 contender, Photo by Greg Ruffing / Redux)

A lot goes into this type of competitive horticulture - “good seeds, good soil, and good luck” as one user puts it on (yep, that’s a thing). Different growers have different tactics. But the common thread among all of these gardeners is the excitement of a truly gigantic gourd and the possibility of next year’s harvest. Jim Myers, a vegetable breeder for Oregon State University, sums it up nicely. "It's something that's interesting to do. There's not a lot of practicality. There might be a little prize money and it's good for notoriety."


5. In Honor of Halloween Part 2: Haunted Forests

Matador Network came up with a list of the 9 scariest forests around the world and the eerie legends that define them. All the creepy legends and ominous imagery wouldn't keep me away from these understories. Only a global pandemic can. Happy Halloween 2020.

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