Bewitched by Buttonbush

As soon as I finished shooting swamp candles Tuesday morning, I turned my attention to a nearby buttonbush. The sunlight was no longer quite so golden, but it was still making great shadow play among the plants.

Cephalanthus occidentalis (Rubiaceae), also called buttonwillow, honeyball, and pond dogwood, ranges from Nova Scotia and Ontario south to Florida and Texas, and is also found in parts of Arizona and California. There are records of it in every Maryland county except Washington.

The multiple stems of this shrub can grow to about twelve feet tall, and the plant can be 6 feet across or more. Foliage is dense and a pleasing shade of green, and how can you not love that inflorescence?

The flower heads measure about one inch across and bear dozens (hundreds?) of flowers, each of which consists of four fused petals, four stamens, and one very long style.

The flowers attract butterflies and bees, and later in the season the seeds attract birds.

Buttonbush is a wetland obligate, meaning that in natural conditions it will be found in wetlands. But there are quite a few of them on the bedrock terrace, which is a dry place except for seasonal flooding and rains. There isn’t much soil there, and no groundwater.

 

Knowing this, I had assumed it wouldn’t make a good garden plant, but I asked the question on a native plant discussion site and got a lot of encouraging replies. It seems that once established, buttonbush does quite well in drier soils. Hooray! Now I just have to find a place for one in my garden.

Pinks and Blues

Up near the Carderock climbing wall there’s a little rocky meadow area that has a delightful variety of wildflowers, usually starting about mid April with wild pinks and azure bluets.

Although the colors range from white through pale pink to bright, dark pink, wild pink (Silene caroliniana ssp. pensylvanica, Caryophyllaceae) is not named for the color, but for the shape of the petals (as if they been cut with pinking shears). Another common name for it is sticky catchfly.

This is a clump-forming semi-evergreen perennial that only grows about a foot tall at the most. It prefers dry to moist well-drained soils in rocky areas, with a bit of shade. It makes a great addition to the rock garden if these conditions are met, but in my garden the rabbits keep sampling it, so I have to use repellent. I don’t think the little beasts favor it, but when competition for food is high, wild pinks are vulnerable.

This subspecies of S. caroliniana is found mostly in the mid-Atlantic states and southern New England, with a few pockets in Ohio, Kentucky, Tennessee, and North Carolina. In Maryland look for it in the ridge and valley, Blue Ridge, and piedmont physiographic provinces, and parts of the coastal plain.

There are two other subspecies of wild pink. S. caroliniana ssp. caroliniana occurs mostly in South Carolina and surrounding areas, while subspecies wherryi is more Midwestern. S. caroliniana (subspecies not specified) is endangered in Florida, threatened in Ohio and Tennessee, and exploitably vulnerable in New York

Azure bluets (Houstonia caerulea, Rubiaceae) is one of four bluet species found in the Maryland piedmont, and can be found in most of the rest of the state, too (it’s missing from a few coastal plain areas). It’s widespread from Maine to Alabama and a few parts of the midwest.

This is a very small plant, consisting of a basal rosette of leaves and a few threadlike stems only a few inches tall, with a flower atop each. The flowers are usually light blue with a yellow throat, though they can range from almost white to moderate lavender blue. Since there can be many stems per plant and it grows en masse, it can be quite eye-catching. Other common names include little bluet, innocence, and Quaker ladies.

I have to admit, this is one of my absolute favorites. I have spent literally hours photographing azure bluets, every spring for the last few years. I can’t get enough of them.

See in the top photo the third type of flower, somewhat taller than the others? More on that next time.

Poor Joe Buttonweed

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poorjoe, rough buttonweed
Diodella teres
(formerly Diodia teres)
Rubiaceae

 

! was really happy to find a member of the Rubiaceae growing in Serpentine Barrens Conservation Park, and even happier to realize it’s a “new-to-me” species. And then I was surprised to learn that it’s considered a nuisance weed of turfgrass. Type “poorjoe” into Google and it will autocomplete to the phrase “poorjoe weed”, and then you’ll find tips on how to eradicate it.

Poorjoe likes disturbed sites and nutrient-poor soils, like in the clear-cut area under power lines where I found these. It’s an annual plant that might sprawl a bit, but is more likely to have ascending stems. The flowers are typically lavender-colored, but there’s some variation and, like a few of the Houstonia species I’ve written about, can appear to be white (or actually be white). They’re borne in the leaf axils. The leaves are sessile, with stipules that form little cups that contain a few long bristles. The stem is often reddish-brown.

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As nuisance madders go, this one isn’t nearly as bad as its cousin Virginia buttonweed (Diodia virginiana). Google that common name, and the whole first page of results will be how to control (kill) it in lawns. Virginia buttonweed is a perennial, sprawling rather than ascending, with white flowers, and no bristles in the leaf axils.

Diodella teres ranges from southern New England south through Florida and west through central Texas, with a few occurrences in the desert Southwest as well. In Maryland it can be found in the Piedmont and parts of the Coastal Plain.

What constitutes a “weed”, anyway? I like this definition: “a plant growing where it isn’t wanted”. I saw only a few poorjoe plants in an area full of invasive aliens, so I’d hardly name it a weed in that context.

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Getting Madders

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Houstonia caerulea (azure bluet)

If you go botanizing during growing season, year after year, you notice trends. For example, there’s almost always something in the Asteraceae (daisy family) blooming, but the family really gets going in high summer and into autumn. Plants in the Violaceae (violet family) bloom in early spring and are done by the time the earliest Lamiaceae (mint family) start. And so on.

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Cephalanthus occidentalis (buttonbush)

This is the time of year for the Rubiaceae, or madder family. Worldwide, it is the fourth largest flowering plant family in terms of number of species (Asteraceae, Orchidaceae (orchid family), and Fabaceae (pea family) are first, second, and third). Depending on which authority you consult, there are about 13,500 species in more than 600 genera.

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Galium concinnum (shining bedstraw); the flowers are about 3/16″ wide

The Rubiaceae is a cosmopolitan family, with species found worldwide except in the polar regions, but most are in the tropics or subtropics. The plants can be trees, shrubs, lianas, or herbs. Some are well-known garden ornamentals (pentas, ixora, gardenia), and some are economically important, producing dyes (like madder), or drugs (like quinine), or beverages (coffee!).

Here in North America, Rubiaceae ranks 18th, with 264 native species. (Asteraceae is first, Fabaceae second, and Orchidaceae ranks 13th.)

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Diodia virginiana (Virginia buttonweed)

In Maryland, Rubiaceae is tied with Onagraceae for 13th place, with 39 species. (Asteraceae is first, Fabaceae second, and Orchidaceae is tied with Plantaginaceae for 9th place.)  I gleaned this information from the Maryland Biodiversity Project but did not weed out the aliens, so if you count only natives the rank may change. But you get the idea.

Geez, this is starting to read like baseball stats.

Anyway, the Maryland species fall into eight genera:

  • Cephalanthus (one species, C. occidentalis, aka buttonbush, found almost statewide)
  • Diodia (two species, D. teres and D. virginiana, both found primarily in the Coastal Plain and Piedmont)
  • Gallium (as many as 24 species depending on taxonomy; distribution varies)
  • Houstonia (five species; see previous post)
  • Mitchella (one species, M. repens, aka partridgeberry, found statewide except Washington County)
  • Oldenlandia (one species, O. uniflora, aka clustered mille-grains; coastal plain)
  • Sherardia (one species, O. arvensis, aka field madder, alien found in the coastal plain)
  • Spermacoce (one species, S. glabra, aka smooth false buttonweed, listed S1/endangered, found in Montgomery County)
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Houstonia purpurea (purple bluet)

Looking at just the sampling of species here in Maryland, you can see traits that characterize the family: flowers consist of four petals, often pointed, partly fused into a tube; there are two leaves or more per node on the stem (opposite or whorled arrangement), the leaves usually entire, and often there are stipules. Most are herbaceous, except partridgeberry, which hugs the ground and never gets more than an inch tall yet has a woody stem, and buttonbush, which is a shrub. I should note, though, that there are many exceptions to these traits in the worldwide accounting of species.

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Mitchella repens (partridgeberry)

 

Variations on a Theme: Venus’ Pride and Longleaf Bluets

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Houstonia species, Rubiaceae

Nationwide there are 18 species of Houstonia, only five of which are found in Maryland; one of those one is found only in Garret County. In the Piedmont, two of these species (azure bluet and Venus’ pride) are rather widespread, and two (longleaf bluet and small bluet) not so much.

Last June I thought I’d found both Venus’s pride and longleaf bluet along the C&O Canal near the Marsden Tract. This year, when I went in search of them I found only Venus’ pride, but I did find longleaf bluet on Sugarloaf Mountain. Here’s a little primer about the two. Their flowers are almost identical; it’s the leaves that differentiate them.

I took measurements of only a few plants, and each patch of plants contained only a few individuals, so consider this casual observation rather than proper science.

A note about color: these flowers were all vaguely purple… in the right light. In some of these photos they’ll look white, which is pretty much how they appear in strong sunlight. In shade the purple, while faint, is more apparent. Despite the moniker “bluet”, they never seem blue.

There’s a little glossary at the end.


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Houstonia longifolia
common names: long-leaved bluet, longleaf summer bluet

  • perianth about 1/4″ long
  • corolla about 3/16″ wide
  • plant height estimated 4-6″
  • leaves opposite, 1/2′ to 3/4′ long, linear shape, one-nerved, margins entire, stipules present

H. longifolia is present in Maryland in parts of the Piedmont and one section of the Coastal Plain, but is found mostly in the Blue Ridge and Ridge and Valley physiographic provinces. BONAP shows it as rare where present in Maryland, but it’s not on the state DNR list of rare, threatened, and endangered plants.

Taxonomic note: MD DNR lists another species, H. tenuifolia, as S1/endangered. However that species is not recognized by ITIS, which considers is a synonym for H. longifolia. What that means for conservation efforts I have no idea.

H. longifolia grows mostly in the Appalachians and Ozarks, and in parts of the Upper Midwest. It’s endangered in Connecticut and Massachusetts, special concern in Maine, and historical in Rhode Island.

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Houstonia purpurea
common names: purple bluet, Venus’ pride, woodland bluet, large bluet

  • perianth about 3/8″ long
  • corolla about 3/16″ wide
  • plant height estimated 4-6″
  • leaves opposite, 1″‘ long, oval shape, three-nerved, margins entire but ciliate, stipules present

H. purpurea is present in the Maryland Piedmont and parts of Coastal Plain. Per BONAP, it ranges through the Appalachians, the Ozarks, and much of the South, but not the Upper Midwest.

ITIS lists three varieties, two of which are endangered in New York; the third is endangered in North Carolina and Tennessee and is also on the federal endangered species list.

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perianth: the sepals and petals of a flower, collectively
corolla: the petals of a flower
ciliate: fringed with hairs
stipule: small, leaf-like growth where leaf meets stem

sources:
BONAP the Biota of North America Program
ITIS the Integrated Taxonomic Information System
Maryland Biodiversity Project

Bluets: A Closer Look

Warning: more than typical amount of plant geekery follows.

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my trusty D3200 poised by some bluets

 

 

 

 

 

As you may recall from yesterday, I went to the C&O Canal to determine if there were indeed two different species of bluets (Houstonia) in the area.

After 15 minutes of walking I arrived at the stand in question, and took a close look.  A really close look.  And lots of pictures.  What I found:

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Two plants, one with five flowering stems, one with three flowering stems.  All were about seven inches tall.

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The uppermost stem leaves were narrow and one-veined.

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The middle and lower stem leaves were oval and three- or five-veined.

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It seems this species is Houstonia purpurea.

 

 

 

I walked another 50 yards or so, knowing that there was another stand somewhere, but I couldn’t find it, so I went back to the first stand and studied it a little more. Kneeling on the towpath and looking around me, I spotted some other flowers that I’d missed while standing.

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This was about eight feet away from the first stand.  It’s a single plant with six flowering stems, all about seven inches tall (just like the first stand).

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Look how long and narrow the leaves are compared to the other plant.  This one is H. longifolia.  I think.  Note the pair of leaves at top and bottom of the picture; they’re a little more oval and rounded at the base.  Could this be an intermediate form?!

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the flowers of H. purpurea…

 

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…are almost identical to the flowers of H. longifolia

 

 

 

Both Venus’ pride (H. purpurea) and longleaf bluets (H. longifolia) can be found across most of the eastern and mid-west US, with the latter species ranging further north and west into Canada. Longleaf bluets are endangered in Connecticut and Massachusetts, of special concern in Maine, and historical in Rhode Island.

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Bluets Illustrate a Lesson in Plant Identification

Houstonia species
Rubiaceae

20150416-20150416-_DSC0359From mid-April to mid-May, the dryer, rocky soils around Carderock will be carpeted in rattlesnake weed and this adorable plant [left].  Standing only a few inches high, each stem bearing a single, terminal flower and few or no leaves, it’s very easy to identify as Houstonia caerulea (azure bluets).

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Half a mile or so west on the C&O Canal towpath, come early June, you might see just a dozen or so of these plants [right] on a certain dry hillside.  Standing about a foot to a foot and a half tall, with a small terminal cluster of flowers and three-nerved, oval leaves, it’s pretty easy to tell that this one is Houstonia purpurea, variously known as large bluets, woodland bluets, and Venus’ pride.

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Here’s when I get into trouble. Satisfied with the identification, I fail to examine every single plant and start concentrating on taking lovely photos, until I get one that I really like.

<—– Like this one.

Yesterday, I posted that photo to an internet discussion group and was quickly challenged: isn’t this Houstonia longifolia (long-leaf bluets)?  Let’s consider it, with descriptions from my three favorite ID books.*

H. purpurea: stem leaves egg-shaped or broadly lance-shaped, with 3-5 veins (Newcomb); plants erect, 6-20″, leaves rounded or notched at the base, stalked or stalkless (C&G); leaves oval, paired, sessile, entire, 3-veined (Peterson).

H. longifolia: stem leaves lance-shaped or oblong, 1-veined (Newcomb); plants erect, 4-10″, leaves narrowly oval or narrowly oblong, 1-nerved, tapering to base, stalkless (C&G); a small plant, slender paired leaves (Peterson).

Note that I didn’t describe the flowers; in all three sources the descriptions pretty much match, but more importantly, there can be a lot of morphological variation in flowers.  Color is probably the worst clue, because it can vary so much.  And look at the previous picture again: can you see that the topmost flower has 5 petals, while the others have 4?  These things happen.  To distinguish these two species, you need to examine the leaves.

Back to the question: which species is pictured?  There isn’t enough information to say for sure. Only the uppermost stem leaves are shown clearly, and while they appear to be narrow and 1-veined, the same can be said of the uppermost stem leaves on the plants ID’d as H. purpurea (in other pictures; I’ll spare you). Is it possible there are two different species in a single stand of plants?  Sure. Is it likely?  I don’t know enough to say.

These things bother me.  As I finish my third cup of coffee, I’m going to hit “publish immediately”, get my camera out, and go to the canal.  If I’m lucky these plants will still be blooming and I’ll get a good look.  If they aren’t, I probably won’t be able to pick them out from all the other foliage in the area.

I’ll post an update later today.

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*Newcomb’s Wildflower Guide; Wildflowers in the Field and Forest (Clemants and Gracie); Peterson’s Field Guide Wildflowers Northeastern/North-central North America