South Dakota Trees: Black Walnut

Black Walnut with spring leaves—its "yearly trick of looking new" (Philip Larkin, The Trees). Union Grove State Park, South Dakota.

Walnuts from a previous year, still unopened. Is extreme toughness adaptive?

Continuing my quest to get to know South Dakota's trees, I chose Black Walnut (Juglans nigra) for this month's tree-following. It's native to the state but barely, probably just in the far east. This is another deciduous hardwood that's common in the midwestern and eastern USA, but rare in South Dakota. Humans have long contributed to the spread of these species, so it can be difficult to pin down their "native" range.

Black Walnut trees can reach 150 ft in height. On open sites the crown is large and rounded. In forested habitat it's smaller, atop a tall mostly unbranched trunk. 

Black Walnut is popular in landscaping; Victoria, British Columbia (TreeLib).

Juglans nigra was once "a dominant and majestic canopy species of primeval midwestern and southeastern forests." But with clearing for agriculture, and harvest for railroad ties, gunstocks, log cabins, furniture, ship-building and more, it became much less common (GoBotany). The venerable giants—to 6 or 7 ft in diameter—are gone. Even so, Black Walnut wood is widely available and quite popular—prized for its dark grain (more information at The Wood Database).

Black Walnut in cross section; photo by Roger Culos.

Black Walnut bowl and photo by Joe Nestlerode.

Juglans nigra leaves are alternate, but often cluster at branch tips and appear whorled (MWI).

Black Walnut usually can be recognized by its leaves, which are long (to 6 dm) and pinnately compound with 8–23 leaflets (terminal one often reduced or lacking). Leaflets are lanceolate, to 15 cm in length, and have serrate margins.

Carl Linnaeus, who named and described the species in 1753, included leaf features in the polynomial name: Juglans foliolis lanceolatis argute serratis—a Juglans with lanceolate leaves with serrate margins. Did Linnaeus mistake leaflets for leaves? Perhaps there was no such distinction in his day.

Black Walnut in Linnaeus's Species Plantarum (1753). Note "nigra" in fine print on right.

In the image above, "nigra", "alba" and "regia" on the page margin hint at a revolution underway. The long descriptive polynomial names were being replaced with binomials (still in use). Species Plantarum is considered the first major botanical work to use binomials consistently. This is where Juglans foliolis lanceolatis argute serratis; exterioribus minoribus became Juglans nigra L. (L. refers to Linnaeus, the authority).

Juglans nigra L. from The Linnaean Herbarium, with permission. Linnaeus did not cite a type specimen in his description, so this one was selected as the lectotype (Reveal et al. 1987).

Like all walnut species, Juglans nigra has unisexual flowers and trees bear flowers of both sexes (i.e., are monoecious). Flowers are inconspicuous—small, yellowish to greenish, with no petals and only tiny sepals. Males form catkins (elongate pendulous clusters) to 10 cm long, with numerous flowers. Female flowers occur in little clusters of 1–4 in leaf axils (where the leaf stem attaches to the branch).

Catkins of male flowers, each with numerous stamens (MWI).

Three female flowers in a leaf axil, each with 2 feathery stigmas (TreeLib).

A female flower has a single pistil. With fertilization, it matures to become ... well ... that depends on whom you ask.

 Juglans nigra fruit, fibrous covering partly removed. Is this a nut? drupe? pseudodrupe? (Plant Image Library)

In their treatments of the Black Walnut, early botanists just described the fruit. The first to do so may have been Mark Catesby, an English naturalist who studied the flora and fauna of the American colonies. In his Natural History of Carolina, Florida and the Bahama Islands (1731) he wrote:

"The thickness of the inner shell requires a hammer to break it. The outer shell is very thick and rough on the outside. The kernels are very oily and rank tasted; yet, when laid by some months are eat by Indians, squirrels, etc." [Kernels are seeds, also called nutmeats.]

Illustrations in Catesby's book "were etched by the author"; plants and animals often were paired, e.g., Black Walnut and American Redstart (relative sizes of fruits and bird are correct) (BHL).

In his 1819 American Sylva, François-André Michaux (featured in this post) provided a bit more detail:

"The husk is thick, and ... when ripe it softens and gradually decays. The nut is hard, somewhat compressed at the sides, and sulcated [with narrow grooves]. The kernel, which is divided by firm ligneous partitions, is of a sweet and agreeable taste, though inferior to that of the European Walnut." 

Black Walnut, by the great botanical illustrator Pierre-Joseph Redouté, in Michaux 1819 (BHL). Male flowers upper left; fruit with green husk lower right next to brown nut.

However it wasn't long before botanists were attempting to assign fruits to defined types. Asa Gray, the eminent Harvard professor of botany, included a system of fruit types in his 1868 Lessons in Botany and Vegetable Physiology. Now 156 years later, it's still in use because botanists haven't come up with anything better. This is not for lack of trying (see Judd et al. 2002, for example).

So what did Professor Gray call the walnut? Well, actually ... he hedged!! In his New Manual of Botany. A handbook of the flowering plants (1908) he called it a "a kind of dry drupe". Dry drupe? But Professor, you defined a drupe as having a fleshy outer part and hard inner part, both derived from the pistil. You provided the cherry, plum, and peach as familiar examples.

As Professor Gray demonstrated, the walnut is not easily categorized. And it's not alone—more than a few fruits confound us in this way.

Parts of a walnut: husk, shell (nut), nutmeat (seed). Wild Harvests.

Some botanists take a strict approach: a fruit must develop from a pistil. This is where the fruit of the walnut—specifically the husk—causes problems. "[It] superficially resembles a drupe, with a hard 'stone' surrounded by a soft, often fleshy husk. The husk, however, is not part of the fruit wall (it develops from the involucre and calyx), and the fruit is actually a nut." (Juglandaceae in Flora of North America).

The Wikipedia Walnuts article mostly agrees, but calls them "accessory fruit because the outer covering [husk] of the fruit is technically an involucre and thus not morphologically part of the carpel [pistil]; this means it cannot be a drupe but is instead a drupe-like nut."

Other botanists are more broad-minded. A fruit with a (relatively) soft outer part and hard inner part can be a drupe, no matter the origins of the parts. Some avoid the controversy altogether by calling the walnut fruit a "drupe or nut" or explaining that it's a nut "but some experts call it a drupe."

That's more than enough discussion of disputed terminology. Let's turn now to something for which there is widespread and probably unanimous agreement. The Black Walnut is a tough nut to crack, in fact one of the toughest!

Cracking a Black Walnut Appalachian style (Blind Pig & the Acorn).

Black Walnut nutmeats are available commercially thanks to "high-tech" processing (video here). But there are alternatives. For those who aspire to collect, clean and crack Black Walnuts themselves, a wealth of helpful information is available online. The most common approach is a hammer, as Mark Catesby recommended nearly three centuries ago. Iowa State University Extension and Outreach explains:

"The hammer method involves placing the nut, pointed end up, on a hard surface and striking the point with the hammer until it weakens and splits into sections along its axis ... shattering of the kernels is often a problem. Shattering can be reduced by soaking the nuts in water for 1 or 2 hours before cracking. The soaking process allows the kernels to absorb enough moisture to become somewhat flexible, resulting in larger kernel pieces."

"Once split, use a pick or plier to remove the kernels inside." (ISU Extension & Outreach)

And for those of us with less patience, John Sankey includes a variety of tools on his Black Walnut Crackers webpage, with tips on use.

The Duke Black Walnut Nutcracker is highly-recommended ($78 on Amazon).

Sources, in addition to links in post

Catesby, M. 1731. Natural history of Carolina, Florida and the Bahama Islands. Volume 1 (Black Walnut p 67). "The illustrations were etched by the author from his own drawings and hand colored under his direction." Catesby also paid for printing. BHL

Gray, A. 1868. Gray's lessons in botany and vegetable physiology. NY: Ivison, Blakeman, Taylor & Co. (BHL).

Gray, A. Circa 1908. Gray's new manual of botany. A handbook of the flowering plants and ferns of the central and northeastern United States and adjacent Canada. NY: American Book Co. BHL

Judd, WS, et al. 2002. Plant Systematics, 2nd ed. Sinauer Associates, Inc.

Linnaeus, Carl. 1753. Species Plantarum 2, p. 997. BHL.

Michaux, F-A. 1819. The North American sylva, or A description of the forest trees of the United States, Canada and Nova Scotia. BHL

Nelson, G, et al. 2014. Trees of eastern North America. Princeton University Press.

Reveal, JL, et al. 1987. On the identities of Maryland plants mentioned in the first two editions of Linnaeus' Species plantarum. Huntia 7:209–246. PDF

South Dakota Trees—why a mulberry is not a blackberry even though it looks like one

Geek alert! (ʘ‿ʘ)╯(photo modified from Flickr).

Continuing my exploration of the South Dakota sylva, this month's featured tree is the mulberry. Supposedly there are two species in the state, more on this later. The fruit is much more interesting.

A mulberry looks a lot like a blackberry—enough so that the Wikipedia article on blackberries mentions mulberries. But blackberries are in the genus Rubus in the Rose Family, while mulberries are in the genus Morus in the Mulberry or Fig Family. And though the "berries" look alike, botanists who know them (as I now do) will tell you they are very different.

Wild blackberry harvest, by Gandydancer.

Fallen mulberries in peak season, by Awinch1001.

Botanically speaking (vs. grocery store produce classification) fruits develop from flowers, specifically the female sexual part(s). Pistil(s) containing ovules mature to become fruit(s) containing seeds. If we run this film backwards—i.e., reverse development—it becomes obvious how different mulberries and blackberries are.

A blackberry consists of tiny fleshy seed-containing units called drupelets, making it an "aggregate fruit". If we run the film backward, we see that each drupelet started as one of many pistils in a single flower.

Blackberries in a range of ripeness, each one a cluster of drupelets; by Ragesoss.

Blackberry flower with many yellow-tipped pistils in the center. Each pistil will become a drupelet; together they will be a blackberry. By I, Luc Viatour.

But if we run the mulberry film backward, we're in for a surprise (I was anyway). A mulberry also is a cluster of little fleshy units, but each of these units started as the single pistil of one flower. In other words, a mulberry develops from a cluster of several to many flowers—an inflorescence! 

Back to the first photo. It's a mulberry—a cluster of fleshy modified flowers.

Female mulberry flowers, each with a single pistil (two styles at tip); the four inflorescences (clusters) will become four mulberries (Minnesota Wildflowers).

Morus flowers are unisexual (often trees are as well). A female flower contains a single pistil that develops into a small dry fruit (achene), while the outer whorl of flower parts (the calyx) becomes fleshy. The result looks like a drupe but is a modified flower. Fruits such as these—formed from multiple flowers—are categorized following a long and venerable tradition.

The great Asa Gray of Harvard University, whose 150-year old system of fruit classification is still in use (because botanists haven't come up with anything better) covered fruits in Lesson 20 of Lessons in Botany and Vegetable Physiology. He started with a brief definition—"The ripened ovary with its contents, becomes the Fruit"—and then immediately addressed an especially problematic situation.

"Some fruits, as they are commonly called, are not fruits at all in the strict botanical sense. ... mulberries, figs, and pineapples are masses of many fruits ... resulting from several or many blossoms, aggregated into one body" (italics mine).

Gray assigned them to the category Multiple or Collective Fruits, as many of us do today (more here).

Asa Gray, "the most important American botanist of the 19th century"; photo from 1870s, source.

Both White and Red Mulberries have been reported for South Dakota. The former, M. alba, is non-native, used for landscaping, and occasionally escapes and persists. Red Mulberry, R. rubra, is said to be native to southeast South Dakota, but so far I've seen no reliable specimens, partly because the two are tough to tell apart.

Their names don't help. The fruit of both can range from white to red and is usually black at maturity but sometimes remains white in White Mulberry. Both have edible fruit, but while red mulberries are sweet and delicious, white mulberries are said to be bland.

Leaves are highly variable in shape, ranging from deeply lobed to entire in both species.

Leaves of White Mulberry, Morus alba, c. 3–4 inches long; Minnesota Wildflowers.

Red Mulberry, Morus rubra, entire and lobed leaves on the same branch! TreeLib.

Flora of North America offers hairiness of leaves as a way to distinguish between the two species (see key to species), but then warns that hairiness is variable in both, perhaps due to hybridization.

During my recent trip to southeast South Dakota, I met a mulberry. Whether it was white or red I can't say. If you-the-reader have mulberry identification tips, please leave a Comment below.

Mulberry tree (Morus sp.) front and center; Union Grove State Park, South Dakota.

Three young mulberries (clusters of flowers).

This is my monthly contribution to the gathering of Tree Followers kindly hosted by The Squirrelbasket. It also contributes to a web-based Guide to South Dakota Trees and Shrubs currently under construction.

Missouri River, South Dakota's Great Divide

"What does the Missouri mean to you?" I was asked.

South Dakota is one of those roughly rectangular states in the heartland of the USA. The Missouri River runs through it north to south, dividing it into two nearly equal but very different halves. To the west landscapes are mostly rugged and sparsely vegetated. To the east they're subdued and covered in plants. So after pondering the sign's question, I decided that was what the Missouri meant to me—South Dakota's Great Divide.

Modified from this map; original source not given.

The difference can be seen even from afar: brown west of the river, green to the east (Google Earth, modified).

The contrast west and east of the Missouri has long intrigued those travelers who pay attention. In 1839 Joseph Nicollet, surveyor with the US Corps of Topographic Engineers, led an expedition up the river as far as Fort Pierre, and then northeast by land. They experienced a dramatic change in landscape almost immediately. The "Great American Desert" west of the river was gone. Instead ...

"... the vast spaces opening to your gaze, the astonishingly richer vegetation, the smoother undulations breaking the monotony, the purity of the water in the streams and rivers flowing into the Missouri, the nature of the woods shading them—everything proclaims a favorable change in the physical aspects of the country." (Nicollet 1843)

Why the sudden change? It can't be moisture. Precipitation does increase going east but only gradually. And there's no significant change in elevation, nothing to disrupt South Dakota's gentle downward slope from the Rocky Mountains eastward. But there is a huge difference in substrate, as Nicollet noted:

[Land east of the river] "is covered by a species of deposite of the kind for a long time known by the name of diluvium; but as this word implies a theoretic idea as regards the accumulation of such deposites, the cause of which is still open to controversy, it is now very generally abandoned, and the designation of erratic deposites, among others, adopted in its stead. I have, therefore, used the latter expression, as comprehending a vast deposite of sand, gravel, pebbles, and clays, ... and masses of rocks transported to a distance from their original position, usually called erratic blocks."

Nicollet's "vast deposite" east of the Missouri is fine ground-up material rich in plant nutrients, with "erratic blocks". Farmers call it "boulder clay". Photo courtesy Dave Rintoul.

In the above description, Nicollet alluded to a controversy surrounding these deposits. In fact, it was a raging debate. Similar material in Europe had long been attributed to the Biblical Flood, but some geologists were pushing a radical new idea—glaciers! After all, these kinds of deposits were associated with modern-day glaciers in the Alps. Even so, most geologists considered the "glacial theory" complete nonsense. Ice sheets at lower elevations in Europe? or on the plains east of the Missouri River? Ridiculous! Nearly three decades would pass before climate change, ice ages and continental glaciers were widely accepted (1).

The Missouri is the west boundary of land once glaciated. But why? (modified from Johnson & Knight 2022).

It's very hard to imagine massive sheets of ice covering eastern South Dakota, especially on a torrid summer day. But they did, and multiple times. Starting about 2.6 million years ago, glaciers advanced south from the Arctic six or seven times, sometimes reaching as far as Kansas and Missouri. Advances alternated with interglacial periods, when the ice melted back. In South Dakota the last ice melted just 11,000 years ago (Gries 1996; Johnson & Knight 2022).

As it flows, a glacier grinds and planes the land and carries off the fragments in its base, making it even more abrasive. When it melts, it leaves behind thick deposits of ground-up material—Nicollet's "erratic deposites", now called ground moraine. After multiple advances and melting during interglacials, eastern South Dakota was covered in ground moraine—the source of the fertile soils east of the Missouri River.

Nicollet's "astonishingly richer vegetation" east of the Missouri River was mostly tall grass prairie. But now it's largely gone, replaced with crops.

Some readers may be wondering, as I did: Why are there glacial deposits east of the Missouri but not to the west? Did the river block the ice? That explanation is tempting, but there's a better one. Look at the map below for clues.

Major streams of South Dakota; modified from Gries 1996.

In the late 1850s and again in the late 1860s (before and after the Civil War), Gouverneur K. Warren of the US Army Corps of Engineers studied the Missouri River and its tributaries. In his 1869 report he described the extensive glacial deposits ("drift") and explained why they stopped at the Missouri, why there were none farther west.

"I have determined the south western limit of the glacial drift action to be the Missouri river ... From the Missouri river to the Rocky mountains, over a space varying from 300 to 500 miles in width, no drift is found ... There, then, on that limit a river must have been formed to carry away the melting water from the glacier, and this limit was the Missouri river, and that was the river formed thereby. It cut along this glacial limit because all the streams west of it came from the mountains toward it, down the inclined plain, and there their old course was terminated" [italics mine].

Many years later, USGS geologist Richard Foster Flint agreed with Warren. "The belief, advanced as early as 1869, that an ice sheet flowing southwestward blocked these valleys and detoured the drainage so as to form the Missouri River is confirmed." As evidence, Flint described three anomalous features of the Missouri (two can be seen in the map above). First, it doesn't follow the gradual decrease in elevation west to the east. In fact it flows mostly south, perpendicular to regional slope. Second, its valley generally is steeper-walled than those of its tributaries, indicating youthfulness. Finally, distribution of its tributaries is very lopsided—all major streams enter from the west (Flint 1955).

In summary, the glacial deposits covering eastern South Dakota end at the Missouri River because that was the limit of glacial advance. But glaciers didn't stop there because of the river. In fact there was no river until ice blocked east-flowing streams, sending them south along the margin of the ice sheet to become part of the longest river in North America—the great Missouri, 2546 miles in length from its headwaters in the Rocky Mountains to its confluence with the Mississippi (2).

President Thomas Jefferson by Rembrandt Peale, 1800 (source).
The Louisiana Purchase was one of Jefferson's greatest accomplishments.

In December of 1803, the United States bought the Missouri River from France as part of the Louisiana Purchase. For only $15 million ($18 per square mile) the young country doubled in size. Six months later, in May of 1804, the Corps of Discovery led by Meriwether Lewis and William Clark started up the Missouri from its confluence with the Mississippi. They had been commissioned by President Jefferson to explore, survey and document the new territory—including its plants, animals, useful resources and human inhabitants. But above all, they were to determine whether the Missouri was part of a water route to the Pacific Ocean.

Travel up the swift-flowing river was terribly slow and arduous. The men paddled, sailed and too often pushed or pulled their boats, including a heavy metal-framed keelboat. (It was sent back down the river from their winter camp, with collections, reports and a map.) It's thought that each boatman ate on the order of nine pounds of meat per day! Fortunately game was abundant (Johnson 2022).

The Corps of Discovery reached the Pacific Ocean in November of 1805, but only after leaving the headwaters of the Missouri, crossing the continental divide, and traveling months by foot and canoe to the Columbia River and on to the coast. Clearly the Missouri did not offer a water route to the Pacific. Even so, it would be an important transportation corridor ... in spite of its treachery.

Navigating Old Misery; from exhibit at USACE Lewis and Clark Visitor Center.

The Missouri, or "Old Misery", was notorious for its unpredictability and lurking hazards. Here's how Joseph Nicollet described his trip on the steamboat Antelope.

"But, notwithstanding the great skill with which the navigation of our boat was managed, and the high power that propelled it, our voyage was sometimes interrupted for weeks, owing to the numerous obstacles presented by the river. It would seem that a Missouri pilot ought to possess not only a quick sight, but an intuitive perception to discover through its turbid waters the channel which yesterday had no existence, presents itself today, and will most probably change tomorrow." (Nicollet 1843)

Hazards included sand bars, snags, and wrecked boats. An estimated 400 steamboats were sunk or otherwise destroyed on the Missouri; the average lifespan of a steamboat was five to seven years (Johnson 2022).

Snags (sunken trees) on the Missouri; by Karl Bodmer c. 1839–1840 (source).

Wrecked steamboat on the Missouri; USACE.

Even after trains and trucks largely replaced boats for transport, the Missouri remained a dangerous river. Large floods were common, causing widespread damage to communities and farmland. But times have changed; the Missouri has been tamed. Between 1933 and 1963, six large dams were built on the river in South Dakota, North Dakota and eastern Montana to provide flood control, irrigation water, hydroelectric power and recreation. About 75% of the river's length in the Dakotas is now reservoir water (Johnson 2022).

In terms of storage capacity Lake Oahe is the largest reservoir on the Missouri. From Oahe Dam near Pierre, SD it extends upstream 100+ miles as the crow flies (modified from Google Earth).

Lewis and Clark Expedition, 150th anniversary issue, 1954 (source).

On a hot day near the end of my trip, I walked four miles sometimes shaded by cottonwoods but usually not and often accompanied by dust and flies, and stood on the bank of a free-flowing stretch of the Missouri River. Why? Because the Missouri means more to me than I first thought.

Memories had been surfacing of a little girl and her younger brother playing Lewis and Clark long ago. Those legendary explorers had struggled up the Missouri, enduring summer heat and mosquitos, surviving winter cold and food shortages, all the while not knowing what lay ahead, what discoveries awaited! Lewis and Clark captured our imaginations, and for me they still do. We lived far from the Missouri then, but now I had a chance to travel where they had traveled, to see the great river flowing as they had.

I started from the parking lot of the Adams Homestead and Nature Preserve north of the Missouri River in the southeast corner of South Dakota. The route followed dirt roads and was well signed. You can tag along on this aerial photo (modified from Google Earth).

Early on we passed Mud Lake, the remains of a meander in the Missouri River before it was tamed (3), and continued past fields being tilled. Then there was a handy rest stop, with a water tub that my field assistant enjoyed in spite of all the flies on her ears (a photo would have been rude). I tried rubbing mosquito repellant on her head—it worked!

A short distance further we reached a viewing platform on the bank of the mighty Missouri.

View downstream. One of the Missouri's nicknames is Big Muddy because its sediment load is huge! (4)

As directed, I looked across the Missouri into Nebraska. Much of the river's broad valley bottom is cultivated but this area looked abandoned, in both the photo below and the previous Google Earth view.

Looking south into Nebraska. The forest in the distance is the valley wall.

Artsy abstract photo for my memory collection :)

Once home I opened the Map of Lewis and Clark's Track, Across the Western Portion of North America to locate the spot where I had visited the free-flowing Missouri. The Corps of Discovery traveled this stretch in late August 1804 after burying Sergeant Charles Floyd, the only death on the expedition (perhaps due to a ruptured appendix). His grave is labeled on the map—Floyds Grave.

From Map of Lewis and Clark's Track. Floyds Grave is right of arrow tip marking my visit (click image to enlarge). Courtesy David Rumsey Map Collection.

Notes

(1) For more about the raging flood vs. glaciers debate and Nicollet's involvement, see Mssr. Nicollet & I consider Glacial Theory and Glacial Beauty in South Dakota.

(2) At their confluence, the Missouri River is longer than the Mississippi River (upstream). By convention the longer river retains its name. Why did the Missouri lose out to the Mississippi? See discussion here.

(3) Nearby McCook Lake (in the upper part of the aerial photo) also is an abandoned meander but is older, being shown on a map dated 1895. Perhaps it's a natural one.

(4) Construction of dams and levees drastically reduced the amount of sediment carried by the Missouri River, to 1% of what it had been (Johnson 2022). Even so, it continues to deliver more than half the silt emptied into the Gulf of Mexico! (more here)

Sources (in addition to links in post)

Flint, RF. 1955. Pleistocene geology of eastern South Dakota. Geol. Surv. Prof. Paper 262.

Gries, JP. 1996. Roadside Geology of South Dakota. Mountain Press Publ. Co.

Johnson, WC. 2022. The Missouri River. Chapter 10 in Johnson & Knight 2022.

Johnson, WC, and Knight, DH. 2022. Ecology of Dakota Landscapes; past, present, and future. Yale University Press.

Nelson, Mike. 2014, Jan 29. Geology: eastern South Dakota in CSMS Geology Post. I also thank Mike for directing me to Flint's 1955 paper.

Nicolett, JN. 1843. Report intended to illustrate a map of the hydrographical basin of the upper Mississippi river. US Senate, 28th Congress, 2nd session, no. 237. BHL

Warren, GK. 1869. General considerations regarding the physical features of these rivers: US Army, Corps of Engineers, Rept. Chief of Engineers, 1868, p. 307-314. Full report online. (Conflicting years are puzzling but real.)

Tree-following: Basswood in South Dakota (barely)

From Trees as Good Citizens (Pack 1922).

"The man who loves trees should be able to identify them at a glance. ... he should make himself familiar with the trees most commonly found in his own section of the country and learn to know them by the names in everyday use." (Charles Lathrop Pack)

Like all tree-followers I love trees. And as Charles Pack advises, I'm on a quest to get to know trees of my "section of the country" (South Dakota). This month I made myself familiar with one common in the far eastern part of the state but otherwise absent—American Basswood, Tilia americana, also known as American Linden or Lime (but not a Citrus or even close). "Bass" probably refers to the tough fibrous inner bark or "bast", used to make ropes and mats.

Basswood in Newton Hills State Park, southeast South Dakota.

Basswood can sprout from stumps, and clustered trunks are common (Minnesota, Eli Sagor photo).

Basswood is a tree of the great Eastern Deciduous Forest ecosystem of midwestern and eastern North America. It reaches the western edge of its native range in southern Manitoba (or possibly Saskatchewan), the eastern Dakotas, and eastern Nebraska, Kansas, Oklahoma and Texas.

Dots mark states and provinces with Basswood, but not specific locations; FNA legacy map, labels added.

This map is common on the Web; arrows added where Basswood ranges farther than shown (Tree Library).

The map above is incomplete because it was made back when plant taxonomists recognized three species of Tilia in North America. But no longer. In his treatment of Tilia americana for the Flora of North America, John L. Strother explained why he recognized only one species and no varieties:

"I tried to see merit in taxonomies in which more than one Tilia species native to the flora area are recognized. In the end, my experiences with specimens and my attempts at using taxonomies that purport to delineate distinct species and/or infraspecific taxa of Tilia in the flora area led me to agree with [a long list of botanists] that taxonomic recognition of more than one native Tilia species in the flora area is not tenable." [This is followed by a thorough discussion of formerly-recognized taxa—read here.]

Strother's decision is fine with me. Being an identifier rather than a classifier, I tend to favor lumpers.

Basswood leaf, flowers, fruit (Pack 1922).

In the case of Basswood, Charles Pack's advice is easy to follow ... sometimes. Trees can be recognized "at a glance" when in flower or fruit. The small yellow flowers form distinctive drooping branched clusters attached by stalks to prominent leaflike bracts. This arrangement persists in fruit.

Distinctive inflorescences of Basswood, in bud; arrows mark where stalks emerge from leaflike bracts.

Basswood flowers are very fragrant and loved by bees (Tree Library).

Basswood fruits are hard round nuts (some sources say drupes, berries, or berry-like; Tree Library).

But without flowers or fruit, Basswood identification can be challenging. Consider the leaves. They are oval to almost round and fairly large (to 15 x 12 cm), with a heart-shaped asymmetric base and serrate margins.

Above and below: broadly ovate Basswood leaves—note asymmetric bases, serrate margins.

Unfortunately Basswood leaves are similar to those of Common or Western Hackberry (Celtis occidentalis), which also grows in hardwood forests in eastern South Dakota. In both species the base of the leaf blade can be asymmetric and margins are serrate. Supposedly Basswood leaves taper to a longer pointed tip (acuminate) while Hackberry leaves have short pointed tips (acute). But in the illustrations and photos I've seen the difference is subtle or maybe nonexistent. Leaf width and shape may be more reliable. Hackberry leaves usually are narrower than Basswood's.

Common Hackberry, Celtis occidentalis (Tree Library).

Bark on mature trees can be helpful. Basswood bark has narrow well-defined fissures, while Hackberry has bark with irregular thick corky ridges or protuberances.

Basswood bark (Tree Library).

Basswood trunks on either side of a corky-barked Hackberry, Newton Hills SP.

Basswood-canopy-gazing on a dreamy afternoon.

In reading about Basswood I couldn't resist a rabbit hole into the world of wood. There I learned that Basswood has extremely fine-grained wood (sometimes described as having no grain). Cells making up the vertical fibers of the tree are small, regular in size and densely packed, producing wood perfect for carving. "A sharp knife or gouge slides through it as if cutting butter" (source).

Basswood lobster under construction, by Dr.DeNo.

Another common use of Basswood is in solid-body electric guitars, for the same reasons. The fine grain and uniform density make machining and finishing easy (source).

Fender JV Modified '50s Stratocaster Electric Guitar, with Basswood body; available at Sweetwater.

Sources (in addition to links in post)

Johnson, WC, and Knight, DH. 2022. Ecology of Dakota Landscapes; past, present, and future. Yale University Press.

Nelson, G, et al. 2014. Trees of eastern North America. Princeton University Press.

Pack, CL. 1922. Trees as Good Citizens. Washington, D.C, American Tree Association. BHL. [This is a guide to planting shade trees.]

Charles Lathrop Pack, 3rd-generation timberman and one of the wealthiest men in the USA in his time, was passionate in his promotion of trees, including proper forestry and conservation. He wrote at least six books on the subject. Date of photo unknown, before 1918 (source).

This is my contribution to the monthly gathering of tree-followers, kindly hosted by The Squirrelbasket. Are you a tree lover? Consider joining us—more information here.