Wednesday, June 13, 2018

Boxelder & Dock at Sunset

Boxelder (Acer negundo) in nook formed by warehouse walls.

The weekend came and went. Weekends are when I usually visit the boxelder I’m following—when no one is working at the warehouse where it grows. But last weekend was really windy, from dawn to dusk. So I waited for a calm evening, and after everyone had left for the day. Finally last night the wind died down at about 8 pm. After dressing for mosquitos, I walked over during the golden hour before sunset, when the sun’s rays pass through more atmosphere and the light is warmer, softer. The smoke plume from a forest fire southwest of town added to the effect.
Smoke plume from Badger Creek Fire.
The boxelder has changed dramatically since my last visit. A month ago, there were no leaves at all, and flower buds were opening on just one branchlet. Now all that’s left of the flowers are dead shriveled stamens (this is a male tree). Now it’s all about leaves—and leaflets, the boxelder’s leaves being compound.
Dangling remains of male flowers.
Boxelder's compound leaves are unusual for its genus—Acer (maples).

There were other changes. Along the base of the warehouse wall, sand dock, Rumex venosus, is in its full glory. Last month it sported flower buds. Now the achenes (seeds) have fully matured, and each is enclosed in inner tepals (undifferentiated petals) which have enlarged, developed reticulate veins, and turned bright pink … or rather a warm rose color in the golden light.
Reticulate veins visible to right of mid photo.
There are now Canada thistles (Cirsium arvense) mixed in with the dock.

Walking home, I saw a shaded patch of dock with the colors I'm used to:

This is my contribution to the June virtual gathering of tree followers, kindly hosted by The SquirrelbasketTree-following is fun! Consider joining us. More info here.

Thursday, June 7, 2018

Botanical Perplexity in the Southern Utah Desert

The bush on the left isn’t dead.
On the Waterfall Trail behind the San Rafael Reef, west of Arches National Park, I came across an unfamiliar shrub. From a distance it looked dead, but up close I saw small green oval leaves with serrated upper margins, and fruit that looked like tiny immature apples. These suggested serviceberry, the genus Amelanchier, and I felt that pleasing cognitive dissonance that comes when something is both familiar and strange. I looked forward to solving the mystery, putting a name on this shrub.
The small glabrous (not hairy) leaves were problematic.
Developing fruit, with anthers and styles still visible.
Serrated leaves and pomes of Amelanchier (Juneberry, Serviceberry); source.

This was supposed to be a short post—put together quickly, just a few photos and some information about the serviceberry, finishing with a sunset. But identification proved elusive, in part due to the small glabrous (hairless) leaves that didn't fit any Utah species, but mainly because of the legacy of struggling Amelanchier taxonomists.

The overlapping and highly variable “species” of this genus confound even the experts. In 1946, eminent botanist Merritt Lyndon Fernald went so far as to claim that no other genus in North America, except perhaps Rubus and Crataegus (raspberries and hawthornes), offered as much “perplexity” as Amelanchier (1).

The serviceberry I saw along the Waterfall Trail is a case in point. For a century botanists have debated its status, moving it from species to subspecies to synonym and most recently back to species. Not surprisingly, my path through the literature was tortuous. But I did meet some interesting characters, starting with Ivar Frederick Tidestrom.
I.F. Tidestrom, photo courtesy USGS.
Ivar Tidestrom ran away from home in Sweden in 1880, and headed for the United States. He served in the US Army (cavalry), enrolled in the University of California as an engineering student, and soon switched to botany. In 1919 while collecting plants in the Charleston Mountains northwest of Las Vegas, Nevada, he found an unfamiliar serviceberry with small glabrous leaves in the “piñon belt near Wilson’s ranch”. Four years later, he published it as a new species: Amelanchier nitens.
Amelanchier nitens, collected by Ivar Tidestrom on May 27, 1919; US National Herbarium.

In the late 1930s, Ira Waddell Clokey, a mining engineer and botanist, was finishing up his intensive study of plants of the same Charleston Mountains. He went to Tidestrom’s site to collect more material of Amelanchier nitens. He concluded it didn’t warrant full species status. Instead, he called it Amelanchier utahensis ssp. covillei (Clokey 1945).
Ira Clokey died in 1950, just after his Flora of the Charleston Mountains was accepted for publication (source).

Around the same time, G. Neville Jones took on a revision of North American Amelanchier, published in 1946. He described Tidestrom’s serviceberry from the Charleston Mountains as an “extreme form” that “intergraded completely with the typical pubescent [hairy] forms” of Amelanchier utahensis, a widespread and highly variable species (2). Thus Amelanchier nitens was reduced to synonymy, becoming part of Utah Serviceberry, where it remained for almost 60 years.

The latest revision of Amelanchier was done by Christopher Campbell and five colleagues, for the Flora of North America (2015 online). In it, I found a species description that matched the serviceberries along the Waterfall Trail pretty well—Amelanchier nitens! So we’ve come full circle. Tidestrom’s serviceberry has been resurrected as a species, now with a common name—Shining Shadbush (shining for the glabrous leaves; shadbush is one of many common names for Amelanchier).
Does Shining Shadbush grow in the “piñon belt” of Utah?

Did I finally have a name for my mystery shrub? Maybe. Unfortunately, Shining Shadbush is said to grow only in the Charleston Mountains in Nevada and in a limited area near Sedona, Arizona, i.e., not in Utah. But then I read the fine print (emphasis added):
“The authors have observed incomplete herbarium specimens conforming to Amelanchier nitens morphology from Colorado, New Mexico, and Utah.”
So the serviceberries along the Waterfall Trail may be the Shining Shadbush, Amelanchier nitens. But given the “perplexities” of serviceberry classification, it’s probably best not to worry about a name. Instead, just enjoy Amelanchier’s approach to biodiversity!

Thus ends my winding tale ... except for the sunset. Here’s one looking south from the Waterfall Trail.
West side of San Rafael Reef, Henry Mountains in distance.


(1) In the Introduction to his American Species of AmelanchierG. Neville Jones (1946) summarized the evolving struggle of taxonomists to classify serviceberries, with wild swings in numbers of species (emphasis added):
“The earlier students [19th century] of the North American flora, including Michaux, Pursh, Nuttall, Torrey, and Gray, took the view that [Amelanchier] in the western hemisphere consisted of only one, or at the most very few, highly variable species. … there now may be found in botanical literature nearly two hundred binomials and trinomials representing the species of Amelanchier in America.”
(2) Jones also described convincingly the challenge of serviceberry identification:
“Anyone who studies Amelanchier in the field, or who examines large series of specimens in herbaria, is at once struck by the extraordinary variation of the foliage that occurs even in the same species, as manifested in different stages of development and from various habitats. … When placed side by side, specimens of the same species in these different stages of development often show an almost incredible dissimilarity and have been not infrequently mistaken for different species.”


Most of these were accessed online via the Biodiversity Heritage Library. Their wonderful collection is newly enhanced with Full Text Search, more information here.

Campbell, CS, et al. 2015 (online). Amelanchier, Flora of North America vol 9.

Clokey, IW. 1945. Notes on the flora of the Charleston Mountains, Clark County, Nevada. Madroño 8:56-61.

Clokey, IW. 1951. Flora of the Charleston Mountains, Clark County, Nevada. University of California Press (Amelanchier pp 119-120).

Jones, GN. 1946. American species of Amelanchier. Urbana: The University of Illinois Press (A. nitens pp 92-93). 

Tidestrom, IF. 1923. New or noteworthy species of plants from Utah and Nevada. Proceedings of the Biological Society of Washington 36:181-184.

Tidestrom, IF. 1925. Flora of Utah and Nevada. Contributions from the United States National Museum 25 (Amelanchier nitens pp 282-284).

Tuesday, May 29, 2018

Dodder—a Dangerous & Desperate Lover

Dysfunctional relationship visible just left and above mid-photo; closer view below.
Driving through the Mojave Desert south of Baker, California, I saw bushes entangled in what looked like finely shredded orange plastic. It was dodder (Cuscuta sp.), also known as the Love Vine. Like a passionate lover, it becomes firmly and intricately entwined with its partner. But this is an insidious embrace. Unable to photosynthesize, the Love Vine repeatedly pierces the vascular system of its host, sucking out water and nutrients.

Dodder has other names, many of which reflect its parasitic nature, for example Witch’s Hair, Witch’s Shoelaces, Devil’s Hair, Devil’s Guts. Damage to the host varies, from minor to deadly, and some dodder species are serious agricultural pests (1).
Unable to stand on its own, devoid of chlorophyll, and with only tiny scale-like leaves, dodder hardly looks like a plant, or maybe a primitive one at most. Yet it’s an angiosperm, a flowering plant, specifically a member of the morning glory family (Convolvulaceae). Most likely the dodder I saw was Cuscuta denticulata, by far the most common one in the Mojave Desert region.
Dodder stems tightly twine around anything within reach.
When I enlarged this photo, I saw I had captured flowers and fruit! (click on image to view)
Toothed petals are source of specific epithet denticulata (S. Matson, Attribution-NonCommercial license).

If dodder finds itself on an appropriate host (verified by chemical sensing), it tightly twines around stems and leaves, growing haustoria in the process—projections that penetrate the host’s vascular tissue.
Developing haustoria of Cuscuta gronovii (courtesy BlueRidgeKitties, some rights reserved).
Haustorium of Cuscuta reflexa in shoot of Nicotiana benthamiana (Kaiser et al. 2015).

But to live the easy life of a freeloader, dodder must first overcome a major challenge—establishment. Its seeds germinate indiscriminately, no matter where they land (seeds of some parasitic plants germinate only in response to chemicals from suitable hosts). Even worse, a dodder seedling has no roots and little in the way of embryonic food reserves, so it must find a host soon, within just a few days (2).

It would seem that only if a seed falls very close to a host plant could the seedling become established. But the situation is not as desperate as it appears. Dodder seedlings are able to “forage” for host plants! After germination, a seedling immediately sets off in search of a suitable host. If it “smells” one nearby, it adjusts its growth accordingly.

Justin Runyon and colleagues (2006) demonstrated that given the opportunity, seedlings of five-angled dodder grow toward their favorite hosts, tomato plants. Using 30 seedlings, the researchers put the basal end of each in a vial of water in the center of a paper disc 9 cm in diameter, with a tomato plant at the edge of the disc. Over four days, they marked on the paper disc the seedling's path of growth (diagrams below are composites for 30 seedlings). For comparison (i.e., a control), they did the same for 30 more seedlings but using pots with just moist soil—no plants.
X marks positions of “targets”: control pot with only moist soil, and pot with tomato plant.
The results were convincing: 80% of dodder seedlings with a tomato plant nearby grew toward the plant, and fairly directly. Those with only a pot of soil wandered more, and were evenly distributed between semicircles (3). The researchers then repeated the experiment using chemical extracts instead of entire plants, and got similar results—73% of seedlings grew toward the tomato-plant extract, and with less wandering. Thus directed growth was specifically in response to volatile chemicals released by the tomato plants (vs. light or color or something else). In other words, a dodder seedling follows its nose (4).

Five-angled dodder also parasitizes wheat, but it prefers tomatoes if given a choice. When Runyon and colleagues isolated the various chemicals in the volatile extracts, they found out why. In addition to several appealing chemicals, wheat contains one that dodder finds disgusting. Tomatoes have no such defense.
Desperate Love Vine approaches its victim.


(1) Dodder can cause significant damage to crops, and is on the USDA Top Ten Weeds List. Eradication is difficult to impossible. Rarely can dodder be eliminated without also harming the host plant. Instead, it’s recommended that the host be removed, and a different crop planted. See Dodder (Cuscuta spp.) Biology and Management.

(2) Some reputable sources say a dodder seedling produces an anchoring root, which dies once a host is found. Sources also differ on survival time for unattached seedlings; they might survive for as long as a week. Perhaps these features vary with species. Cuscuta pentandra seedlings can grow just a few centimeters on their own, but even so, in a field of tomatoes or wheat, plenty of seedlings will find a host.

(3) Runyon and colleagues also did these experiments with paper discs divided into quadrants rather than two semi-circles, and obtained similar results.

(4) In their supplementary materials, Runyon et al. provide a very cool movie of a wandering dodder seedling searching for and finding a host! Click on “Movie 1” to download.


Kaiser, B., et al. 2015. Parasitic plants of the genus Cuscuta and their interaction with susceptible and resistant host plants. Front. Plant. Sci. 6: 45.

Runyon, JB, Mescher, MC, and De Moraes, CM. 2006. Volatile chemical cues guide host location and host selection by parasitic plants. Science 313: 1964-1967.

Monday, May 14, 2018

The Mailbox on the Sill—the short & the long of it

The Palisades in Cimarron Canyon, northern New Mexico.
Browsing through my photos of the Cimarron Canyon Palisades, I spotted an odd form on the crest which I hadn’t noticed when I was there. Is that really rock? Zooming in showed nothing to suggest otherwise. But how improbable!
I’m hardly the first to spot this weird finger of rock. Years ago someone thought it odd enough to add to the Devil’s collection of landforms and landmarks—Devil’s Postpile, Devil’s Backbone, Devil’s Thumb, Devil’s Racetrack, Devil’s Marbles, Devil’s Gate, etc. In this case, we have the Devil’s Mailbox.
Devil’s Mailbox; Pomona Public Library, Frasher Foto Postcard Collection, 1938.
Unfortunately, the Mailbox story ends here, as my “research” (Google) produced no further details. In contrast, the story of its context is much longer, on the order of 40 million years. The Mailbox is part of the Palisades sill, a massive sheet of igneous rock intruded into sedimentary strata of the Cimarron Range. This may have happened during creation of the range, part of the Laramide Orogeny, the mountain-building episode that built the Rocky Mountains. In a later episode of uplift, maybe 20 or 30  million years ago, the Cimarron River cut down through the range revealing part of the sill, in cross-section. The dramatic exposure is called the Palisades, and is part of Cimarron State Park. There’s a convenient pullout at the base, along US Highway 64.
Actually, the details are still being debated.
As of 2002, geologists were still debating the exact age and composition of the sill. Dating has produced ages ranging from 35 million years to as young as 26 million. Rock composition also has been hard to pin down (see this page for citations):
“Based on mineralogy and chemical composition, the Palisades consist of biotite-diorite porphyry. Other geologists have called the rock type of the Palisades a monzonite porphyry, quartz monzonite porphyry, dacite porphyry, a granodiorite porphyry, or a transition from trachydacite to dacite. Although these terms describe the rock properly according to its composition, some terms are inconsistent with its texture. Therefore, the term porphyritic dacite seems the best description of these sills.”
The rock looked porphyritic to me, i.e., large phenocrysts in a matrix of fine-grained rock. This is easy to see in the blocks lining the pullout.
The columns and towers of the exposed sill are spectacular. They're separated by long vertical joints that formed as the intruded magma cooled, underground. Later, water seeped into the fractures, and froze and expanded in winter, slowly breaking the rock. This went on for millennia, producing talus slopes at the base (and rock blocks for the pullout).
Talus slope at base, apparently stable enough for trees to grow large. 
The Palisades Sill Official Scenic Historic Marker is on US Highway 64 in Cimarron Canyon State Park, about 8.3 miles east of Eagle Nest and 15.5 miles west of the town of Cimarron (36.537449° -105.152374°). The Mailbox stands near the northwest end of the ridge visible from the highway.


The Palisades sill is included in New Mexico’s Virtual Geologic Tour, a terrific trip-planning resource. The Cimarron Canyon State Park page includes a substantial list of references.

Monday, May 7, 2018

Boxelder News: some sensationalism this month

Photo by M Nelson.
The standard approach shot—boxelder in shady nook, with no obvious changes.
When I rounded the corner of the warehouse yesterday, on my monthly tree-following visit, I could see no obvious changes in the boxelder. But as I got closer, I saw that its neighbors were coming to life, like dandelions along the ramp to the warehouse door.
And what looked like windblown debris from a distance turned out to be sand dock, Rumex venosus, currently in bud. The red winged fruits are spectacular, but we will have to wait at least a month for those.
Sand dock in bud.
As for the boxelder … buds were opening, but only on one branchlet, one of the first to catch sun in the afternoon. These look like flowers buds with emerging anthers, therefore a male tree.
Male boxelder flowers, photo by Kruczy89; source.

Meanwhile, 177 miles south of Laramie and about a thousand feet lower, a boxelder at Lowe’s is fully leafed out, displaying fresh green foliage with a hint of copper. In summer, the leaves will be rich green, and then turn pale red in autumn—hence the name, Sensation Box Elder. It’s said to be “the best known plant discovery of Warren Carnefix, the Idaho plantsman and nurseryman whose family will mark 100 years in the nursery industry this year.” (J. Frank Schmidt & Son Co.)
Sensation Boxelder front center, among arboreal offerings at Lowe’s (M Nelson).
A hint of copper in spring leaves (M Nelson).
Fall foliage (source).
The Colorado Springs Rock Guy was surprised to find a boxelder in a nursery, having lived around boxelders and the notorious boxelder bugs as a kid in Kansas. “I have never, never seen anyone, at least from Kansas, plant a boxelder tree. I have seen many persons cut them down or grub them out.”

But according to J. Frank Schmidt, the “seedless nature of this male clone makes it less attractive to box elder bugs, a pesky but harmless insect [trees show no obvious signs of injury] that feeds on the flowers of female trees and takes refuge in houses in the fall.”

The University of Minnesota Extension says the same: “Starting in mid‑July, they [boxelder bugs] move to female seed-bearing boxelder trees where they lay eggs on trunks, branches, and leaves. They are rarely found on male boxelder trees.” Even female trees get the Extension’s support: “In our opinion, the benefits of having these trees in a landscape outweigh the problem of occasional infestations.”

More than a few people agree. There are even boxelder bug fans, some of whom adopt and name the invaders of their homes. See Thank Goodness for Boxelder Bugs by the Prairie Ecologist, and the numerous comments, almost all positive.

This is my May contribution to the virtual gathering of tree-followers, kindly hosted by The Squirrel Basket. More news here.