Weakley Flora to the Rescue! (With a Primer on Using Botanical Keys)

upper stpem, leaves, and inflorescence

upper stem, leaves, and inflorescence

The day after writing the previous post, I returned to Serpentine Barrens Conservation Park armed with a 10X lens, a small knife, a ruler, a notebook, and most important, a printout of page 1126 of the Flora of the Southern and Mid-Atlantic States by Alan S. Weakley, determined to key out my unknown goldenrod species.

Success! I keyed it out in the field, but collected a sample to photograph at home with the macro lens.

If you’re interested in how botanical keys work, keep reading. If you just want to know which species it is, skip to the end.

The first couplet in Weakley’s key reads:

1  Leaves with numerous slightly raised, pale, translucent, blister-like pustules; leaves transmit light when held up; plant glabrous………E. leptocephala
1  Leaves without pale pustules, or if present then leaves opaque and do not transmit light; plants glabrate to pubescent.

Glabrous is smooth, glabrate means “almost smooth”, and a pubescent area is covered in short hairs.

closeup of stem and leaf base showing hairs

closeup of stem and leaf base showing hairs

 

Have a look at this photo. Clearly the plant is hairy, so I chose the second line, which leads to this couplet:

 

 

 

2  Major veins on leaf underside 3-5 (if 3 then all 3 veins bold), leaves 5-12 mm wide; heads with 20-50 flowers.
2  Major veins on leaf underside 1-3 (-5) (if 3 or 5 then only the midvein bold), leaves <6 mm wide (-8 mm wide in E. gymnospermoides); heads with 10-20 flowers.

leaf base, underside

underside of leaf at base

In the field I measured the largest leaves that were still intact on the plant. (All the lower, presumably largest, leaves had turned brown and curled up and many had fallen off.) Most of them were in the 7-8 mm range. Every leaf I examined had five veins, though some were pretty hard to see. Given these facts, I chose the first line of couplet 2 (more about the flower heads later), which leads to

3  Leaves 3-6 (-8) mm wide, punctae on leaf upperside bold, flower heads 10-20 flowered………..E. gymnospermoides
3  Leaves 5-12 mm wide, punctae on leaf upperside obscure or not bold, flower heads 20-50 flowered.

Again based on leaf width, and the fact that the punctae (dots) were not bold, I chose the second line, which leads to

4  Leaf undersides, upper stems, and branches glabrate, often with villous hairs on midrib of leaf underside …………………E. graminifolia var. graminifolia 
4 Leaf undersides, upper stems, and branches copiously to moderately short villous
…. E. graminifolia var. nuttallii

Look at the first picture again; I’d call that copiously villous. (“Villous” means covered in soft hairs.)

flower heads (7/32" long)

flower heads (7/32″ long)

About the flowers… Remember that plants in the Asteraceae have composite flowers. That little thing next to the ruler in this picture, measuring only about five and a half millimeters long, is a flower head – a collection of flowers. At least, it was, as these had all turned to seed. I was able to cut some open and tease out the seeds. I didn’t count more than 20 in any single head, which suggests about 20 flowers (each flower produces one seed). But, they were minute, and I was working with a small knife and a 10X hand lens, so it’s quite likely my count was inaccurate. Since I couldn’t get a true count of flowers per head, I ignored that part of the key.

seeds

seeds

So there it is. My mystery grass-leaved goldenrod/goldentop is Euthamia graminifolia var. nuttallii.

The More I Learn, the Less I Know

Readers of this blog will have noticed that I am fascinated by names. It isn’t enough for me to spot a plant and say “that’s a goldenrod”; I need to know which goldenrod, the actual species name, what other common names there might be for it and what the Latin words translate to and how it relates to other species… and pretty much anything else related to its taxonomy.

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No plant has led me into taxonomic Wonderland like this one —>.
I first saw it at Serpentine Barrens Conservation Park, in late August in bud, then in October in flower (kind of).

Right away I recognized it for a goldenrod, yet it looked a little different from other goldenrods. The flower heads weren’t in plumes or in the leaf axils like other goldenrods I know. So I took a few pictures, went home, and opened the books. It was easily categorized into “flat-topped goldenrods”, sometimes known as goldentops, for which Newcomb lists two Solidago species and Peterson lists four; Clemants and Gracie list two Euthamia species and two Oligoneuron species.

Hmm. Time to open more books.

Melanie Choukas-Bradley, in An Illustrated Guide to Eastern Woodland Wildflowers and Trees (2004), describes a lance-leaved goldenrod, Solidago graminifolia, noting that it’s also called Euthamia graminifolia, and also noting that “some botanists…consign the flat-topped goldenrods to a separate genus (Euthamia).”

Fleming, Lobstein, and Tufty, in Finding Wildflowers in the Washington-Baltimore Area (1995), report seeing “lance-leaved goldenrod (Solidago graminifolia)” in the area where I found this plant (they call the area the Potomac Power Line).

At this point I had tentatively decided that what I found and photographed would currently be called Euthamia graminifolia. I decided to run it by a few experts for confirmation. That’s when I learned that Euthamia is a “problem genus”.

Now I was really interested in learning what was going on, so I consulted a bunch of internet sources, and that’s when things got a little crazy.

In short, the USDA PLANTS Database lists six Euthamia species, not all of which are found in the Maryland Piedmont. BONAP lists five, only one of which is in the Piedmont. MBP lists four, only one of which is in the Piedmont. ITIS recognizes four species, and lists thirty-six Latin synonyms for E. graminifolia. Thirty-six!

Now totally confused, I consulted even more authorities, and found the following:

from EOL

 Euthamia is a genus of flowering plants in the aster family, Asteraceae.[2][3] They are known commonly as goldentops[4] and grass-leaved goldenrods.[5][6]

The species were formerly classed in genus Solidago, the goldenrods. They were separated on the basis of morphological differences, such as the arrangement of the flower heads in the inflorescence and the glands on the leaves, and of DNA data.[7] Authors have recognized 5 to 10 species.[5]

from the Astereae Lab:

Euthamia… is a small genus of erect, herbaceous perennials native to North America. Sierren (1981) revised the genus and recognized nine eastern species and one western species. Haines (2006 Flora North America) recognized only five species. Euthamia was incorrectly included in Solidago by many authors for a more than a century. Cronquist (1981) accepted the distinct generic status for this group of species on the basis of morphology and leaf anatomy (Anderson and Creech 1975).

Lane et al. (1996) showed that the on the bases of cpDNA, Euthamia was phylogenetically not close to the true goldenrods with a number of other genera more closely related…

Unfortunately, the practice of placing the grass-leaved goldenrods in Solidago continues and leads to errors in interpreting the results of ecological studies.

 

And finally, Flora of the Southern and Mid-Atlantic States (Alan S. Weakley, 2015) lists six species, with the note that Euthamia is

A genus of about 8-10 species, herbs, of North America. There are a number of serious problems remaining in our knowledge of Euthamia.

Apparently so.

Weakley’s key is excellent, and if I can get back to the park before the plant is done blooming, I might be able to key it out. Stay tuned…

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on-line sources

USDA PLANTS Database
BONAP (The Biota of North America Program)
MBP (Maryland Biodiversity Project)
ITIS (Integrated Taxonomic Information System)
EOL (Encyclopedia of Life)
Astereae Lab (University of Waterloo)
Weakley Flora (The University of North Carolina Herbarium)

Silverrod

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aka white goldenrod
Solidago bicolor
Asteraceae

This is one of only two species of Solidago that isn’t golden, though if you look closely you’ll see that the disk flowers are often pale yellow while the rays are white.

Confusingly, the other white flowering species is called upland white aster, but despite the common name is actually a goldenrod, Solidago ptarmicoides.

Silverrod is a plant of the eastern US and Canada that ranges as far west as Missouri, Quebec in the north, and south to the Gulf Coast (but not Florida).  It’s a low-grower, seldom exceeding two feet, and prefers drier soils in open woodlands.

I never have managed to get a really good picture of it, for some reason.

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Blue Stem

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blue-stem goldenrod, aka wreath goldenrod
Solidago caesia
Asteraceae

 

As I wrote previously (and last year), goldenrod identification can get really tricky. Both zigzag goldenrod and blue-stem goldenrod have unusual characteristics, though. For one thing, they’re woodland plants (most goldenrods like full sun, or at least more sun). And they bloom relatively late. And few other goldenrod species have flower clusters in the leaf axils; most goldenrods have terminal, or at least upper-stem, inflorescences.

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Whereas zigzag has big, oval, serrated mid-stem leaves, bluestem has linear, smooth-edged or serrated, one-nerved leaves that are sessile, all the way along the stem, which may or may not carry a slight blue tint. Better to rely on leaf shape and the presence of axillary flowers for identification.  As you can see from the photos, it will sometimes have an upright habit, but more often flops over under the weight of the blossoms.

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The specific epithet is from the Latin caesius, meaning cutting or piercing.

Blue-stem goldenrod can be found from Texas in the south and northeastward into Quebec.  It’s endangered in Wisconsin.

Bent Stem

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zigzag goldenrod
Solidao flexicaulis
Asteraceae

 

 

 

 

The late summer not-quite drought wiped out a lot of flowers, but others are starting to bloom after the recent rains. The earlier goldenrods are mostly gone, but this is one of two later-blooming species that are coming along nicely.

With over 70 species in the continental US (two dozen of which occur in the mid-Atlantic Piedmont), it can be difficult to distinguish one Solidago from another. This species is an easy one, though, with large, serrated, ovate leaves with petioles at the middle of the (usually) unbranched stem, and upper stem leaves that are lanceolate. In most specimens, there’s a bend at each node, hence the name “zigzag” goldenrod.  (The specific epithet, flexicaulis, means bent stem.)

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zigzag goldenrod typically has only a few ray flowers; in this photo you can see the opened disk flowers

 

 

 

 

 

Zigzag goldenrod is found east of the Rockies except in parts of the deep South. It’s threatened in Rhode Island.

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and in this photo, the disk flowers have not yet opened

Update on “Yet Another Goldenrod” (FotD 9/22)

It appears that one of my mystery goldenrods is Solidago racemosa.  This might not interest you much, but it interests me because although it is a rare plant throughout its range, it can be found pretty readily along the rocky bluffs of the Potomac gorge.

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It’s a compact plant, only growing a foot or so tall, with leaves both on the stem and forming a basal rosette.

Although S. racemosa has several different common names, none of them are commonly used.  It’s gone through several botanical name changes, too, formerly known as  S. simplex and S. spathulata.

Just about everything you’d care to know about the Solidagos can be found in the goldenrods section of the Astereae Lab web page of the University of Waterloo in Canada.

S. racemosa is endangered in New York, Massachusetts, and Pennsylvania; threatened in Tennessee; and of special concern in Kentucky.