Tree Following: Killer Cottonwood in Utah

On a hot afternoon several weeks ago, I pulled into Hittle Bottom Campground on the Colorado River in southern Utah. After parking in the only site with shade, I opened the windows, put screens in place, inserted $10 in the payment envelope, and started for the pay station. But I was stopped in my tracks by a Killer Tree, right next to our campsite!

The area around it had been cordoned off with orange caution tape, but I checked carefully to make sure we were safe. Indeed everything was fine. We were out of range of falling limbs.

Click on image to view caution tape, marked by arrows.

The big cottonwoods that grow along lowland rivers in North America—Populus deltoides and P. fremontii —are infamous for dropping large dead branches. As the Colorado AAA has observed:

No one writes poems about “under the spreading cottonwood tree” because it can actually be dangerous to sit under a cottonwood in high winds due to breaking branches.

The technical term for this is "dieback".

Some cities (Denver for example) ban these cottonwoods in part because of dieback. They grow fast (to six feet per year!) and are relatively short-lived, so falling limbs will be a problem. And they grow roots toward and into reliable water sources such as city water and sewer lines! This is an impressive adaptation for the trees but a problem for us (source).

The Hittle Bottom Campground has no water aside from the river, so managers don't worry about cottonwood roots invading plumbing. But dieback is a problem, hence the caution tape. Of course I wanted photos, so I risked my life so in the absence of imminent danger (the day was calm) I stepped over the tape to commune with the Killer Tree.

Zig-zag form due to lost branches.

The bark was especially photogenic, even with tape.

This is Fremont's Cottonwood, named to honor the famous explorer and surveyor John Charles Fremont. However the honor probably celebrates another of his achievements, one less widely known—botanical discovery! Fremont was not a taxonomic expert but he knew how to collect plants. And collect he did—on the order of two thousand specimens. Among these were at least 165 species new to science, some 40 of which were named in his honor. For more about Fremont's botanizing, see JC Fremont was here.

On the afternoon of March 30, 1846, Fremont and his party "encamped on Deer Creek, another of these beautiful tributaries to the Sacramento [River, in California]. Mr. Lassen, a native of Germany, has established a rancho here ...". They stayed for five days, during which time Fremont collected plants, including a cottonwood. He suspected it might be a new species, as he had noted the previous year when he was in southern Utah (no collection was made or survived).

Fremont's 1846 specimen from "Deer Creek at Lassens" (Gray Herbarium). He collected both male (above) and female (below) flowers, demonstrating knowledge and care in collecting plants.

Typical of field botanists at that time, Fremont relied on experts for identification. He sent many of his collections to the leading American plant taxonomist—Asa Gray at Harvard. Gray often passed along western specimens to his colleague, Sereno Watson, who was more familiar with that flora. It was Watson who named and described Populus fremontii.

Sereno Watson (Wikimedia). A colleague described him as "tall, very erect, [with] good features, a high-bridged nose, and a carefully tended beard of great length and whiteness. Almost to the end of his life he walked with a brisk elastic step suggesting physical energy remarkable for a man of his years."

In his 1875 paper, Watson distinguished P. fremontii from its close relatives "especially by the remarkably developed torus" (now called floral disc). He also noted that young growth tended to be somewhat hairy. In contrast, the similar P. deltoides has smaller floral discs and young growth is not hairy.

A century later, James Eckenwalder, expert on the genus Populus, reached the same conclusions, recognizing the larger floral disc and often hairy young growth as distinguishing features for Fremont's Cottonwood (see also his treatment in Flora of North America).

Populus fremontii from Sargent's 1896 Silva of North America; added enlargement shows female flower with floral disc—thought to have evolved from petals and sepals.

Fremont's Cottonwood with capsules and young leaves (TreeLib, J Morefield photo).

Mature leaves and bark, Fremont's Cottonwood (TreeLib).

These last photos are included in part to thank Blake and Nathan Willson for their wonderful Tree Library website—"a digital platform for teaching and studying trees with a focus on promoting awareness and understanding of trees and their global importance to the environment."

Fremont's Cottonwood, Rio Grande, New Mexico. "Trees are our silent partners, sensing us as we move about, providing shelter, offering us beauty, and nurturing and protecting the earth." (TreeLib)

Addendum, 23 Oct 2024. Posch, BC, et al. (2024) found Populus fremontii to be super efficient at leaf cooling (via transpiration) even when temperatures exceed 48 °C (118º F)! But water must be available. Even a minor disruption in availability will shut down cooling, causing leaves to overheat. See Intensive leaf cooling promotes tree survival during a record heatwave. 

https://doi.org/10.1073/pnas.2408583121

Sources, in addition to links in post

Eckenwalder, JE. 1977. North American cottonwoods (Populus, Salicaceae) of sections Abaso and Aigeiros. J. Arnold Arboretum 58:193–208 [P. fremontii p. 198-200] BHL.

Fremont, JC. 1887. Memoirs of my life: including in the narrative five journeys of western exploration during the years 1842, 1843-4, 1845-6-7, 1848-9, 1853-4 Internet Archive.

Sargent, CS. 1896. The silva of North America: a description of the trees which grow naturally in North America exclusive of Mexico. Vol. 9 (P. fremontii p.183 ...) BHL.

Watson, S. 1875. Revision of the genus Ceanothus, and descriptions of new plants ... Proceedings American Academy of Arts & Sciences. Vol. 10 (P. fremontii p. 350) BHL.

This is my October contribution to the monthly gathering of Tree Followers, kindly hosted by The Squirrelbasket.

Desperate to post about a tree

One problem after another, most recently–this morning–a dead laptop, hopefully temporarily. I resurrected an old one, and in spite of being pretty demoralized (this on top of COVID 19 (I mean the craziness, I'm not sick)), I'm attempting to be part of the monthly tree-gathering, so kindly hosted by The Squirrelbasket. More news from tree followers here.

I didn't make it to LaBonte Park yesterday. After "rehearsal" during which we (University symphony orchestra) performed for ourselves, and clapped when we were done (5 weeks of work down the drain due to COVID cancellation), I went outside to snow. That would be Laramie snow, traveling sideways in the strong winds. So we went home.

Instead, we walked down to see an old tree friend, the cottonwood on the Laramie River that I followed in 2015. Here are a few photos.

Reaching and crossing the Laramie River, just a five minutes from home :).

My cottonwood friend, on far side of river, just left of center.

Crossing river on footbridge, with a bit of fresh snow from yesterday.

Ice floating downstream, probably anchor ice from river bed that cut loose.

Tree isn't doing much—of course. This is 7200 ft in the heart of the continent.

No sign of flowers or leaves. How about some bark instead? Old is furrowed, young is smooth and pale.

Best wishes to all, and stay healthy!

Should there be trees where once there were none—even though once (as now) there were many?

Cottonwoods, boxelders and willows along the Laramie River at Fort Laramie, on a hot day in 2016.

In southeast Wyoming, on the Laramie River just above the confluence with the North Platte, Fort Laramie still rises from the prairie. From its beginnings in the 1830s as a private fur-trading post, until the US military abandoned it in 1890, it was the most important outpost on the Northern Plains. Trappers, traders, Indians, emigrants, gold miners, soldiers and settlers all came here—for commerce, supplies, advice, news, negotiations, peace-making and war. For many, it was their only connection to the civilized but hostile world back East.

In 1849, the US Government bought the property from the American Fur Company to establish a US Army post, in part to make clear to Britain and Mexico that this was United States territory. The most important mission was protecting the tens of thousands of west-bound travelers who passed through each year on the Oregon/California Trail—probably the largest single land migration in history.

Most emigrants had “jumped off” at the Missouri River, and had been on the trail for over a month when they reached Fort Laramie. They averaged on the order of just 15 miles per day in the sweltering heat of the Great Plains, breathing dust churned up into great clouds by hooves, wagon wheels and human feet. The Fort was a welcome layover—a place to rest and fatten livestock, wash clothes, and repair wagons. It was one of the few places on the long journey to buy supplies.

Fort Laramie was about a third of the way from the Missouri River to the coast (source).

In the early 1850s, some 50,000 travelers were arriving at Fort Laramie each year! The total between 1841 and 1866 may have been 350,000, or as high as 500,000. These numbers speak to how difficult and dangerous life was for many people in the early days of our country. More than a few had lost everything to events beyond their control. What else could they do but leave, in hopes of something better? We were fortunate to have the huge sparsely-populated West and all it promised.

Immigration—ever the hopeful path to a better life. Painting by Alfred Jacob Miller (wikimedia).

My first visit to Fort Laramie was in July 1999, to prepare a vegetation map for the National Historic Site. It was hot! One afternoon while surveying open rolling country covered in sagebrush and grass, we came upon deep wagon ruts. They were overgrown but still obvious—remains of the Oregon Trail. Standing in the broiling sun, I looked down on the Laramie River several miles away, and was struck by how blessed and inviting its lush green gallery forests must have appeared to early travelers.

But I was wrong. There were no trees along the river at Fort Laramie during the great migration, no shade to soothe weary souls. They had been cut down years earlier, for buildings and fuel.

My misguided historical imaginings fell apart last week, when I returned to the Fort and saw this photo:

Crow delegation at the Fort Laramie council site in 1868 (from park interpretive sign).

Fort Laramie was an important council site. Indians set up camp on a large flat area east of the Laramie River, and prominent tribal leaders—Smoke, Red Cloud, Man Afraid of His Horses, Spotted Tail—met and negotiated with representatives of the US Government. Today, an interpretive sign near the river explains: “The ridgeline in this image [above] can still be seen if one looks east across the Laramie River.” But one has to look carefully to spot any landmarks, as the council site is now largely hidden from view by trees.

Should trees blocking the historical view be cut down? (arrows mark points on ridge visible in old photo)

In the absence of trees, what was used for fuel? I asked the friendly historian at the Visitor Center, who explained that the Army had a timber reservation on Laramie Peak 50 miles to the west; there was a lumber mill nearby. Soldiers were detailed to cut wood, and haul milled lumber and firewood back to the Fort. Though it was nice to get away—tedium and boredom being the biggest problems at Fort Laramie—it was dangerous. Lieutenant Levi P. Robinson met his end on a wood-cutting detail, killed by Indians. (Though there were skirmishes nearby, the fort itself was never attacked, being large and well-defended.)

When the Army closed Fort Laramie in 1890, trees were returning to the river. A century later, with cottonwood groves well established, a debate arose: if there were no trees during the historical period of interest, do today’s interfere with re-creation of those times?

Fort Laramie in 1875, viewed from across the tree-less Laramie River (source).

Fort Laramie in 1889, a year before it was abandoned. Trees line part of the river (source).

Fort Laramie in 2009, with cottonwoods, boxelders and willows along the river (Google Earth).

In 1980, historian Merrill J. Mattes argued in defense of historical accuracy:

“… need to have proper understanding and respect for the Fort's historic setting as well as its buildings. Over the decades the persistent efforts to plant parade ground trees which never existed during the "period of maximum importance," and to defend the post-1890 cottonwood grove along the river from any historical vista clearing … suggest that Park Service planners and managers have never been overly concerned with the sanctity of the historical setting.” (Mattes 1980; italics added).

I have to admit, the "cottonwood grove along the river” definitely confused my interpretation of the historical setting! It was more harsh than I had imagined. Perhaps some trees could be cleared to restore the historical view of the council site, but I think it would be fine to leave the rest. Last week, with temperatures in the 90s, I happily took a break in the shade of cottonwood trees along the river. It didn’t diminish at all my appreciation for how tough those early travelers were!

During our mapping project in 1999, we often took our lunch break in the saloon, cooled by an electric fan. “I’ll have a cold sas’sprilla” I’d say, pounding my fist on the bar in true Western style. Did soldiers and emigrants at Fort Laramie really have the option of an ice cold drink in the sweltering heat of midday? Most likely not, but I was sure glad we did!

On my return visit last week, I again headed over to the saloon, pounded my fist on the bar, and said, “I’ll have a cold sas’sprilla.” The bartender obliged. It was just as refreshing as I remembered.

Fort Laramie National Historic Site is open year-round, no charge. Dogs are allowed on leash (outside). Summer days are hot, but maybe that’s the best time to visit if you want the real emigrant experience (peak visitation back then was late May to early July).

• • •

This is my contribution to the July gathering of tree-followers, kindly hosted by The Squirrelbasket. In lieu of following a specific tree (too much work and travel), I’m posting about trees, at least for a few more months.

Sources

Buck, R. 2015. The Oregon Trail. Highly recommended (The New York Times agrees).

Mattes, MJ. 1980. Fort Laramie park history 1834-1977. National Park Service. Last updated 2003; available here.

National Park Service. 2014. Fort Laramie brochure. Available at the park.

Old photos, drawings and other images of Fort Laramie are available here (no charge for non-commercial use). Unfortunately there’s little information about the scenes and sources.

Winter on the Laramie River—great food, wrong trees

Would you camp here for five months?

On September 4, 1831, twenty-one fur trappers packed their mules, saddled their horses, and rode up the Laramie River from the North Platte. They would travel until they found beaver, then trap until snow and cold sent them back downstream. But things did not go as planned. It would be May before they finally returned, and they would have to walk back.

Among the trappers was 22-year-old Zenas Leonard, one of the many young men who joined the fur trade for economic gain and adventure. He left the family farm in Pennsylvania the year before after announcing, “I can make my living without picking stones.” Zenas was a literate man, and kept notes during his travels. In 1839, he published a book about his five-year journey through the Rocky Mountains: Narrative of the Adventures of Zenas Leonard (available free here). The following account of a winter on the Laramie River is based on Leonard’s Narrative.

NOT Zenas Leonard; added in error by GoogleBooks. See note at end of post.

Traveling was easy at first. “… found the prairies or plains very extensive—unobstructed with timber or brush—handsomely situated, with here and there a small creek passing through them, and in some places literally covered with game, such as Buffaloe, White and Black tailed deer, Grizzley, Red and White Bear, Elk, Prairie Dog, wild Goat, Big horned mountain Sheep, Antelope, &c.”

But when they arrived at “the foot of a great mountains through which the Laramies passes” they found it impossible to continue, as “huge rocks projecting several hundred feet high closed it to the very current.” Instead, they traveled along the base of the Laramie Range to a buffalo trail leading to the crest, where they made camp. At midnight it began snowing hard, and they were forced to stay put for three days.

Not bothered by the early-October blizzard, the party continued on to the Laramie Valley. Leonard described it as long and broad “with the river Laramies passing through the centre of it, the banks of which are covered with timber, from 1/4 to 1/2 a mile wide … on a clear morning, by taking a view with a spyglass, you can see the different kinds of game that inhabit these plains, such as Buffaloe, Bear, Deer, Elk, Antelope, Bighorn, Wolves, &c.”

Beaver were abundant; they trapped twenty the first night. Then they continued upstream, periodically stopping for a few days to trap. Clearly the Laramie Valley was worth the trouble of getting there.

Base map by John C. Fremont (drawn by Charles Preuss), 1848; from David Rumsey Historical Map Collection. Insert below; click on images for larger views.

Trappers' route from the confluence of the Laramie and North Platte Rivers to the Laramie River campsite (X). Precise locations of their route across the Laramie Mountains and campsite are unknown. At that time, the Laramie Mountains were often called the Black Hills.

By October 22, the days were consistently cold and snowy. All agreed it was time to return to winter quarters on the North Platte. They followed the Laramie River back downstream to the buffalo trail across the mountains. But … surprise! It was no longer passable—there was too much snow. Several men searched for an alternative route but found none. In the discussion that followed, “a majority of the company decided in favor of encamping in the valley for the winter.”

The river was the obvious place to stay. Game was abundant. Cottonwood trees would provide wood for shelters, fuel for heat, and nutritious inner bark for horses and mules when grass was buried in snow. Camp was established on November 4.

“… we arrived at a large grove of Cottonwood timber, which we deemed suitable for encamping in. Several weeks were spent in building houses, stables, &c. necessary for ourselves, and horses during the winter season. They [the best hunters] killed buffalo and dried meat in case the herds left the valley. They killed deer, elk, antelope and other game & dressed the hides to make moccasins.”

By early December, the horses were struggling to find grass. The men collected armloads of cottonwood bark, but “to our utter surprise and discomfiture, on presenting it to them they would not eat it, and upon examining it by tasting, we found it to be the bitter, instead of the sweet Cottonwood.” By the end of December, most of the horses had died (apparently the two mules were less picky). They celebrated the New Year anyway.

“On new-years day, notwithstanding our horses were nearly all dead, as being fully satisfied that the few that were yet living must die soon, we concluded to have a feast in our best style; for which purpose we made preparation by sending out four of our best hunters, to get a choice piece of meat for the occasion. These men killed ten Buffaloe, from which they selected one of the fattest humps they could find and brought in, and after roasting it handsomely before the fire, we all seated ourselves upon the ground, encircling, what we there called a splendid repast to dine upon. Feasting sumptuously, cracking a few jokes, taking a few rounds with our rifles, and wishing heartily for some liquor, having none at that place we spent the day.”

Food and fuel remained abundant, but the men grew restless. Someone had heard they could buy horses in Santa Fe, so all but four men headed south on foot with beaver skins to trade. Two weeks later, they were turned back by snow and dwindling supplies of food. By the time they returned to the Laramie River camp they were gaunt and hungry, but quickly fattened up on game.

Finally, on April 20, they loaded what they could on the two weakened mules, cached everything else, and headed east across the Laramie Mountains through deep snow. Back on the plains, they stopped at the first sweet cottonwoods they came to and let the mules feast on inner bark for several days. They reached the North Platte on May 20, 1832.

Why no one in the group recognized the Laramie River cottonwoods as the bitter type is puzzling. Travelers as far back as Lewis and Clark could distinguish between the sweet and bitter types, even without leaves, and knew that horses would not eat the bark of the latter.

Were they an ignorant bunch? After all, they crossed the snowy Laramie Range in October, trapped beaver in the Laramie Valley into early November, and rang in the New Year with gusto in spite of losing all their horses, intending to walk to Santa Fe to get more.

Or were these trappers skilled adventurous men not averse to hardship? Maybe for them it was no big deal to spend five wintry months camped on the Laramie River before walking back to the North Platte!

Bitter cottonwoods (left; now called narrowleaf cottonwoods) grow at higher elevations, including the Laramie Valley (7000 feet). Sweet cottonwoods (Plains cottonwoods) are trees of lower elevations.

ADDED NOTE (May 21, 2016): In digitizing Leonard's narrative, GoogleBooks added a portrait to the cover as an enhancement—but it was the wrong one! Thanks to Scott Stine for tracking down the source of the error, and notifying Google:

[the] "digitized version of the 1904 edition displays a portrait, labeled 'Zenas Leonard,' on the first (digitized) page. But that portrait is not of Zenas Leonard; rather, it is of Michel Sylvestre Cerré. The portrait comes from (opposite) page 146 of the 1904 book (which appears on page 143 of your digitized version), where it is correctly labeled 'Michel Sylvestre Cerré.'"

• • •

This is an expanded version of an article I wrote for Laramie's Living History—a series produced by the Laramie Boomerang and the Albany County Museum Coalition.

Hollis Marriott
Contributing History Columnist

Getting to Know a New Friend(s?)

Lucy of Loose and Leafy has stepped up her efforts to organize and encourage tree-followers.  This is very kind, as tree-following is always interesting and it's fun to share discoveries.  We choose a tree to follow through the year, and there's so much to learn.  What kind is it and how do we know?  When do leaves appear? flowers, fruit?  Who lives there?  How does it catch the sunrise?  Does it do justice to the golden hour just before sunset?  These are all important things, and it’s our responsibility to find out.

Stirred by Lucy’s enthusiasm, I took my camera with me on my morning walk along the Laramie River.  It’s still winter here, so I got side-tracked by the beauty of river ice.

Center foreground -- our tracks from last week, now inverted because most of the snow has blown away.

Footbridge across the river, once a railroad bridge.

Shadow patterns cast by grass, brush and trees.

My field companion, as faithful to me as his shadow is to him.

I returned to my mission and soon chose a tree for 2014 (below left).  Or maybe I should say “trees” as there are multiple trunks.  Most of the trees along the river grow this way, in clumps.  Is this a single individual, connected underground?

Winter landscapes can seem so dreary.  But if we can get out of that black-and-white mode caused by snow, we realize there's quite a bit of color after all.

Another view -- the tree stands over its cousins, the willows.

Its twigs appear bare at first glance.  A closer look (click on image) reveals buds ready for spring.

Trees often are challenging to identify without leaves, but I gave it a shot.  I ran a dead leaf through the Rocky Mountain Tree Finder, partly because I love dichotomous keys and this one is so easy to use.  How does it work?  At each step I pick one of two choices, thereby eliminating a substantial number of tree species from consideration.  I continue this way until the only one left is the one I’m standing under!  It seems like magic, even after all these years.

In this case, the path to identification required 14 steps, including the following:

1) Leaves needle or scale-like OR ordinary?  ordinary

2) Leaves compound, composed of several leaflets OR simple?  simple

3) Leaves paired on opposite sides of twigs OR not?  not (no leaves, so checked leaf scars)

4) Leaves lobed OR not?  not

5) Leaf stalks (petioles) longer than 1 inch OR less than?  less than

... etc. ...

10) Leaf margin with big & little teeth OR single-sized teeth?  single-sized

Leaf margin with single-sized teeth.

and finally:

14) Leaf tips often blunt rather than sharply pointed OR not?  often blunt rather than sharply pointed (see illustrations below)

It appears to be the narrowleaf cottonwood, Populus angustifolia (click on image for more information).

I also attempted to identify the tree with the Winter Tree Finder.  This is challenging because the useful characters are harder to see and not as familiar.  I had to look at terminal buds, leaf scars and vein scars -- so let’s digress.

From the Winter Tree Finder.

The terminal bud is where the twig will start the year's growth.  Leaf scars are left when leaves fall off.  They contain vein scars -- remnants of conduits (phloem, xylem) for transporting water, nutrients, carbohydrates and more.

Now back to identification.  I went straight to the cottonwood section.  The Winter Tree Finder says terminal buds of cottonwoods are symmetrical.  According to the Audubon Society's Field Guide to North American Trees, Western Region, terminal buds of the narrowleaf cottonwood are resinous and smell of balsam.  Let’s look:

The terminal bud is indeed symmetrical, and somewhat resinous too.  I didn't detect a balsam odor.

The Winter Tree Finder says leaf scars of cottonwoods are crescent-shaped with three vein scars.  Sure enough, there are three vein scars on each crescent-shaped leaf scar:

The leaf scar below the bud is from last year; the one near the base of the twig is probably two years old.

The terminal buds, leaf scars, and vein scars of my tree all match those of cottonwoods.  But I couldn’t go any further in the Winter Tree Finder because it covers the eastern USA, and Wyoming is in the west.

I'm sure this is a cottonwood and probably a narrowleaf cottonwood.  The bark looks right:  “smooth, becoming gray-brown and furrowed into flat ridges at the base” (Audubon Society Field Guide to North American Trees, Western Region).  It's growing in the right kind of habitat -- lowlands or near water -- and well within its range (see previous map).

I will check my tentative identification after the tree leafs out, but first it will bloom and I'll need to investigate that as well.  Cottonwoods have unisexual flowers, either male or female, and the sexes are on separate trees (dioecious).  Thus I’ll learn whether this clump is male or female -- or maybe both, suggesting these are separate trees after all.

Cottonwoods along the Laramie River, in winter morning sun.

However I shouldn't dwell on tree activity right now.  It's only February.  Cottonwood flowers and leaves won't appear for months yet, probably in May, at least that's what I think I remember.  I don't always notice -- but this year I will.

Are you following a tree?  Sign up here or here to join the fun.