Astery Things #2: The Joe-Pye Weeds

Eutrochium fistulosum

Once upon a time there was a genus of plants called Eupatorium. It was a large genus, lumping together plants commonly known as thoroughworts, bonesets, mistflowers, snakeroots, and joe-pye weeds. Roughly twenty years ago, the genus was split into twelve or more genera. Thoroughworts and bonesets are still Eupatoriums; mistflowers are now Conoclinium, and snakeroots Ageratina. Joe-pye weeds, those plants with large arrays of pink-purple flowers and whorled leaves, were placed in the new genus Eutrochium.

Eutrochium maculatum

Historically, four of North America’s five Eutrochium species were found in Maryland, but one of them, E. maculatum (spotted joe-pye weed), has been extirpated. The other three are

  • E. dubium (eastern or coastal plain joe-pye weed)
  • E. fistulosum (hollow joe-pye weed, trumpetweed)
  • E. purpureum (sweet, sweet-scented, or purple node joe-pye weed)

Distinguishing these four species from one another is fairly straightforward, provided you can look at mature, flowering specimens. Here is a much abbreviated chart of some identifying characteristics, taken from the Flora of North America, with the most useful ones in bold purple:

  E. dubium E. fistulosum E. maculatum E. purpureum
stems
purple-spotted purple purple spotted dark purple at nodes
  sometimes solid purple sometimes spotted sometimes solid purple greenish to purple-green
  solid hollow solid; may be hollow at base solid; may be hollow at base
leaves
arrangement in whorls of 3-4 in whorls of 4-6(-7) in whorls of (3-)4-5(-6) in whorls of 3-4(-5)
venation 3-nerved pinnately veined pinnately veined pinnately veined
shapes deltate-ovate narrowly lanceolate lance-elliptic lance-ovate
  ovate broadly lanceolate lanceolate ovate
  lance-ovate lance-ovate deltate-ovate
margins coarsely serrate finely serrate sharply or doubly serrate coarsely serrate
bases abruptly contracted gradually tapered gradually tapered gradually tapered
or abruptly tapered or abruptly tapered
florets
number (4-)5-9(-10) (4-)5-7 (8-)9-20(-22) (4-)5-7(-8)
notes
found only in coastal plain over 6 feet tall wide distribution known to hybridize
  and inland along major rivers morphologically variable morphologically variable

When trying to identify plants in the field, remember to look at the totality of characteristics rather than focusing on one or two, because there can be so much variation from plant to plant. And also because you really shouldn’t be cutting into plant stems in the field, at least not in areas where plants are protected.

E. fistulosum: hollow stem

Here are a few pictures to illustrate. Keep in mind that these are garden plants; wild-growing specimens rarely look so lush and full. Also, the E. maculatum pictured in this post is not the species, but rather a cultivar (‘Gateway’). Still, it’s not too far off what a wild plant looks like.

E. fistulosum: a whorl of 4 broadly lanceolate leaves

E. fistulosum: a loose corymb of flower heads

 

 

 

 

 

 

 

 

 

 

 

 

 

 

E. maculatum: whorl of three leaves, purple-spotted stems

 

And here are a few of E. maculatum. It’s worth noting that further up on the stems, the leaves were in whorls of four (but I couldn’t get a good picture up there).

E. maculatum: lanceolate-ovate leaf

 

 

 

 

 

 

 

 

 

Eutrochium species with purple node

This picture from four years ago is probably of E. purpureum, though I was never able to get close enough for a confident ID. At any rate, it shows what a purple node looks like.

 

Of course none of this is what makes joe-pye so interesting. It’s those flowers. Unlike the aster I wrote about in the last post, joe-pyes have no ray florets – only disc florets. Each floret consists of five pointed petals, fused at the base, from which a single long style emerges. The cumulative effect of all those tiny flowers, from 4-24 per head, dozens of heads in each corymbiform inflorescence, up to a dozen inflorescences on each stem, often multiple stems from one plant… it’s just breathtaking.

And then there’s the icing on the cake: joe-pye weeds attract bees and butterflies like crazy.

More about this next time.

 

Purpurea

Continuing with pretty pictures during this cold season. It’s a thin line between blue and purple. Color is a continuum. Color is in the eye of the beholder. If some of these look more blue or pink than purple, well, c’est la vie.

Triodanis perfoliata (Venus’ looking glass; Campanulaceae)

Look for this annual forb growing in rocky places where there isn’t much competition from other plants. It generally blooms from about mid May into early June here in the Maryland piedmont.

Clinopodium vulgare (wild basil; Lamiaceae)

A perennial forb with circumboreal distribution. Look for the flowers in the height of summer.

 

 

Cunila origanoides (common dittany; Lamiaceae)

A perennial native to North America, and found mostly in the mid West and mid Atlantic. It blooms in late summer.

 

Elephantopus caroliniana (Carolina elephant’s foot; Asteraceae)

A rather weedy-looking plant with a fascinating inflorescence. Click on the picture and look closely; you’ll see that this is actually four disk flowers, each with a five-lobed corolla. The species is native to the southeastern US (Maryland is almost as far north as it goes). It blooms in late summer.

 

Eutrochium purpureum (sweet joe-pye weed; Asteraceae).

The joe-pye weeds (formerly Eupatorium species) are perennials that love wet places, but this particular species tolerates drier soils and is a great native for the home garden, with dramatic heads of colorful flowers towering above most other forbs. And it attracts butterflies. Blooms in late summer.

Mentha arvensis (field mint; Lamiaceae)

Another mint-family plant with circumboreal distribution. Another late-summer bloomer.

 

 

Mimulus alatus (winged monkeyflower; Phrymaceae)

Watch for this wetland plant and its almost identical cousin M. ringens var. ringens (Allegheny monkeyflower) blooming in early to mid summer.

 

Monarda fistulosa (wild bergamot; Lamiaceae)

The mint family sure is represented well here. Look for it in mid summer, possibly covered in bees and butterflies.

 

Phlox divaricata (woodland phlox, wild blue phlox; Polemoniaceae)

As you can see this flower ranges from almost white through lighter and stronger shades of blue and purple. They bloom at about the same time as Virginia bluebells. Bluebells grow in the floodplain while this phlox grows just upland of the floodplain, in still moist (but not wet) woodland soils.

Physostegia virginiana (obedient plant; Lamiaceae)

Yet another mint family mid summer bloomer. Watch for it on rocky outcrops and gravel bars in the Potomac.

 

 

 

 

Ruellia caroliniensis (hairy wild petunia; Acanthaceae)

In Maryland this species is found mostly in the Coastal Plain; in the piedmont it’s restricted to a few sites near the Potomac River (as far as I know – please leave a comment if you know otherwise). Watch for it in late spring and early summer.

Trichostema dichotomum (forked bluecurls; Lamiaceae)

Blue or purple, or splitting the difference? Whatever. This is a most striking plant, one of those OMG finds. Well it was for me, anyway. What a lurid color. Late summer, dry soils, open areas. Yow.

Verbena hastata (blue vervain, swamp verbena, Verbenaceae)

As one of the common names suggests, you’ll find this in wetlands, blooming anywhere from late June to mid August. This is an extreme closeup; the plants are rather tall but the inflorescences rather small.

 

 

Vernonia noveboracensis (New York ironweed; Asteraceae)

All ray flowers with strongly exserted stigmas, no disk flowers. Very tall plant, wispy appearance. Likes wet soils. Blooms in mid to late summer.

 

Viola palmata (early blue violet, three-loved violet; Violaceae)

Violet taxonomy is in flux, and violet species can be difficult to differentiate. This one is relatively easy because of the unusual leaf shape, although even that can be highly variable. Look for it in mid spring in drier woodlands.

One Reason to Plant Native Flowers

 

 

 

 

 

When I don’t have time to write meaningful content, I post pretty pictures. Here are a few of a spicebush swallowtail on Eutrochium fistulosum (joy-pye weed, Asteraceae) in my garden. The plant also attracts monarchs, eastern tiger swallowtails, and lots of skippers and bees.

I hope to get back to writing some time next week. Apologies for the lapses.

The Aster Family (part 5): Odds and Ends

Did you know that there’s a word for the study of the Asteraceae? It’s synantherology. And, a person who studies the Asteraceae is a synantherologist.

I was going to write a post about the lower orders of classification within the aster family. But it ends up being unusually complicated, with various authors positing sub-families, super-tribes, tribes, sub-tribes, and even sub-genera as ranks between family and species. If you’re really interested, check out the Asteraceae page at the Tree of Life Web Project, or Classification of Compositae from the International Compositae Alliance.

So rather than another detour into taxonomy, here’s a gallery of aster family oddballs: flowers that might not look like composites at first glance.

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Anaphalis margaritacea
pearly everlasting

Maryland Biodiversity Project has only 2 records for this plant, including one in the piedmont, so it’s unlikely you’ll see it in this area. But you’ll see it often in floral arrangements. The yellow-ish centers are the disk florets, and the white outer parts are bracts; there are no ray florets.20140915-DSC_0024


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Antennaria plantaginifolia
plantain-leaved pussytoes

This plant is found throughout the Maryland piedmont. White disk florets only, surrounded by green phyllaries. Look at those little seeds!
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Elephantopus carolinianus
Carolina elephant’s foot

Found throughout the Maryland piedmont. Click on the image and then zoom in to see the details: this head is showing four individual disk florets, each with a five-lobed corolla. There are no ray florets.

 

 


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Erechtites hieraciifolius var. hieraciifolius
pilewort; fireweed; burnweed

Found throughout the Maryland piedmont. My apologies for not having a clearer picture. The flower heads contain disk florets only (no ray florets).


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Conoclinium coelestinum
blue mistflower
(with eastern tailed-blue butterfly)

Found throughout the Maryland piedmont. Disk florets only.

 

 


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Eutrochium purpureum
sweet joe-pye weed
(with eastern swallowtail butterfly)

Found in most of the Maryland piedmont.  Disk florets only.
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Flower of the Day: Sweet Joe-Pye Weed

 Eutrochium pupureum; Asteraceae (aster family)

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Those wacky taxonomists are always re-naming things.  The genus formerly known as Eupatorium contained a large number of species, a few of which I’ll be featuring over the next several days.  Colloquially they’re known as joe-pye weeds, thoroughworts, bonesets, and snakeroots.   Apparently the joe-pye weeds are now in the genus Eutrochium (for a while they were in the genus Eupatoriadelphus).

There’s a lot of folklore around the medicinal uses of this plant, named for a Native American who used it for a variety of ailments.  It’s a plant with a lot of presence, growing to seven feet tall in rich, constantly moist soils all over the eastern half of North America.

DSC_0024 Has a slightly sweet scent, too.  If you have a swale at the back of your yard where nothing wants to grow, plant some joe-pye weed in it as the backdrop for a perennial border.

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