Tickseed Sunflower, Taxonomy, and Terminology


Bidens species


As beggarticks go this one is rather showy. I found vast stands in Serpentine Barrens Conservation Park late last month, but wasn’t sure which of the many Bidens species they were. How to tell? First, I considered species known to be found in Maryland, then eliminated many choices based on flower form (many are small and/or non-showy). Next, I looked closely at the leaves. Only a few Bidens species have pinnate leaves with very narrow leaflets. But once I narrowed it down to these species, I ran into a problem.





According to one paper referenced by Wikipedia, “the taxonomy of Bidens has been described as ‘chaotic’.”  So I made a little chart to try to sort it out, and narrowed the choices to

  • Bidens aristosa, a name recognized by BONAP, USDA PLANTS, ITIS, and MBP [see end note]
  • Bidens coronata, a name recognized only by USDA PLANTS
  • Bidens polylepis, a name recognized by ITIS and MBP
  • Bidens trichosperma, a name recognized by BONAP, ITIS, and MBP

Since searches for B. coronata mostly led to B. trichosperma, I ruled out the former as a defunct name, no longer used by most authorities.

Searches for B. polylepis sometimes led to B. aristosa. According to the website uswildflowers.com, “most authorities have merged B. polylepis into B. aristosa.”


ITIS has been my go-to, though I recently learned of the existence of a soon-to-be published flora of Maryland, which is MBP’s standard. Since the remaining three species are recognized by both these authorities, I focused on them.  And the New England Wild Flower Society’s excellent gobotany website came to the rescue.

Identifying species in the Asteraceae often comes down to close examination of the seeds, which these plants weren’t producing yet. But there were enough other details that I could finally name this specimen B. polylepis, based on these characteristics:

  • B. aristosa: inner, non-herbaceous involucral bracts eciliate or ciliate; peduncles pubescent
  • B. polylepis: inner, non-herbaceous involucral bracts coarsely ciliate; peduncles pubescent
  • B. trichosperma: peduncles glabrous

Or, to put it in plainer language:

  • B. aristosa: the leaf-like parts immediately under the flower heads may or may not have hairy edges; the flower stem is downy
  • B. polylepis: the leaf-like parts immediately under the flower heads have coarsely hairy edges; the flower stem is downy
  • B. trichosperma: the flower stem is smooth


In Maryland, Bidens polylepis can be found mostly in the Coastal Plain and the southern Piedmont. It likes moisture and sun, often in disturbed areas, like clear-cut areas under power lines. The plants can grow up to four feet tall. The main stem may branch, and each branch may have one to three flower heads.

Common names for B. polylepis include tickseed sunflower, long-bracted beggarticks, long-bracted tickseed sunflower, bearded beggarticks, and Ozark beggarticks.

I write this blog for the fun of teaching myself botany and taxonomy (and to share pretty pictures and “gee isn’t this neat” discoveries), so I’m not an expert (yet). Please leave a comment if you believe I’ve gotten something wrong!


The abbreviations used above refer to

(links are to each site’s Bidens page).

bract   a modified leaf located under a flower (like the “flowers” of poinsettias or common dogwood)
ciliate   having hairs on the margins (eciliate  without hairs on the margins)
glabrous  smooth
involucre   the part of the plant surrounding or supporting a head of flowers
peduncle   the part of a stem supporting a flower head; flower stalk
pinnate   describes a compound leaf with leaflets on either side of a midrib (actually rachis, but really how detailed should I get here?)
pubescent   downy

Gardening With Native Plants: Resources

This past Saturday I went to the Northern Alexandria Native Plant Sale, a nice event that wasn’t full of people running around like crazy (though there were plenty of crazy plant people), and plenty of vendors, too. And I’m happy to report that many more vendors are selling retail these days, though most require an appointment. Here’s a partial list. All of these places had a good selection of interesting plants that appeared to be in good health (otherwise I wouldn’t be listing them).

Chesapeake Natives, Inc. “Promoting, Protecting, and Propagating Plants Native to the Chesapeake Region” – the tag line pretty much says it all. Straight species is all they sell (no cultivars).

Enchanter’s Garden (soon to be Wood Thrush Nursery) “We specialize in growing plants native to the southern Appalachian Mountains and beyond.”

Go Native Tree Farm  “Dedicated to the understanding, preservation, and recovery of the Eastern American forest.”

Hill House Farm and Nursery This place did have some cultivars among the species.

Kollar Nursery “Kollar Nursery specializes in plants native to the eastern United States…we propagate most of what we grow.”

Putnam Hill Nursery seemed to have less emphasis on “straight species” but still had plenty of interesting ones.

The sale organizer’s webpage seems to be down until next month, so the link may not work, but for reference: http://home.earthlink.net/-sknudsen/id3.html. And here’s the facebook page: https://www.facebook.com/NorthernAlexandriaNativePlantSale

Most of these places were only selling what’s “in season” – flowering, that is (trees and shrubs excepted). If you’re looking for spring and early summer blooming plants, try again in those seasons. Spring ephemerals are a tough sell out of season – look, a pot of dirt! – but when the season comes ’round they are in high demand.

A word of warning: while researching I stumbled upon a list of “some of the many [nurseries] nationwide that specialize in native plants” published by the US Fish and Wildlife Service Chesapeake Bay Office. At first I was thrilled, but when skimming it realized that it isn’t accurate. Some of the nurseries listed are large operations that I know from experience may carry native plants, but do not specialize in them. I include it for the sake of information, but do sift through it. Caveat emptor.

If you have a favorite native plant nursery, especially one that eschews cultivars, please leave a comment!

Gardening with Native Plants

It’s a good time of year to be installing plants in the garden, especially shrubs and trees, so on a recent Saturday I dragged Steve along on a field trip to Herring Run Nursery in Baltimore.

Native plant gardening is becoming a little more popular every year, as people learn more about the benefits of natives and the detriments of alien invasives. The benefits are obvious once you think about it: natives are adapted to the environment so need less watering, fertilizing, soil amending, deadheading, and pruning; are generally pest-resistant, so pesticides aren’t needed, or if they are attacked by pests, they aren’t destroyed; are good hosts for butterflies; provide food for wildlife.

But establishing a native plant garden isn’t easy.



Is Spigelia marilandica native enough? Despite the specific epithet, this plant does not occur naturally in Maryland. But it is found nearby. Kind of.


First, good luck finding a supplier of quality plants if you’re just a homeowner. Many native plant nurseries are “too the trade only”. Some of them will open one or two times a season on a weekend for retail sales, which is great but you have to wait for those days. Or you can go to a native plant fundraiser sale, a type of event that’s becoming more popular, but wow can those things be a zoo. I remember getting to one half an hour before opening and was something like 20th in line, and everyone in front of me had carts or wheelbarrows.

I do almost all my own gardening, so I bristle at the thought of going through a garden designer or landscaper to get material. Not to mention I have a low opinion of most landscaping contractors, but that’s a rant for another time.

Another issue is finding genuine native plants, by which I mean species, not cultivars. We humans have been practicing genetic engineering for about as long as we’ve been human (the argument’s been made that our practice of genetic engineering is one of the things that made us human). Find a tasty plant in the wild? Cultivate it, watch for improvements in succeeding generations: better flavor, faster ripening, longer fruiting time, larger yields per plant, larger fruits, better disease resistance, ease of handling and transport, more appetizing color, pleasing aroma, and on and on. Then selectively breed the plants that show the desirable traits, et voila! the cultivar is much improved over the species.

We do it with ornamentals as well as food plants. Double-flowering, longer blooming, more perfumed or not as stinky, different colors, dwarf or strongly upright forms… almost every plant in your garden is a cultivar (“cultivated variety”) of a naturally occurring species, if not a hybrid (inter-species cross breed).

Guess what? Many of the “native” plants in the nursery trade are cultivars, too.  Want a species joe-pye weed? Good luck finding Eutrochium maculatum. You probably can’t. What you can find is Eutrochium maculatum ‘Gateway’ -a cultivar*.

So what’s the big deal?, you wonder. What’s wrong with longer bloom time or improved disease resistance? Gardens are fantasies of nature anyway, right?

Yes, but. The problem is that sometimes – not all the times – the native fauna you hope to attract will not recognize your cultivar as a desired plant, so they won’t be attracted to it. Or maybe they will recognize the plant, but the cultivar’s structure (eg. double-flower) makes it impossible for pollinators to get to the nectar. Or the cultivar is sterile and doesn’t produce seed for birds to eat. So if you’re planting natives to attract the birds and the bees and the butterflies, do some research, and whenever possible, buy the species instead of a cultivar.

Then there’s the problem of defining “native”.  About 20 years ago I was with a Master Gardener group that was planting a demonstration xeriscape in a public space. One of the MGs had chosen Gaura lindheimeri for the garden.

“Is that a native?” I asked.

“Of course it is!” she replied.

“But it’s not a Maryland native. It’s a midwestern plant.”

“Close enough”.

In a way, she was right. This species is a good choice for a xeriscape: it’s a North American native with no aggressive or invasive tendencies. And back then there’s no way you could have filled a garden with Piedmont ornamentals, unless you poached them. Nobody was growing them commercially.

Besides, many of our native Piedmont species are not particularly showy. Or they have short blooming periods, like twinleaf (Jeffersonia diphylla), which is very showy but blooms for five days at the most. You have to be a real botanerd to appreciate some of these plants.



Scutellaria ovata: in Maryland, there are only records for it in Washington County. Is it native enough for my Montgomery County garden?



So it all comes down to two things: how narrowly you want to define “native”, and what you want from your garden. If you’re planting to benefit the local fauna, choose species over cultivars whenever possible, but you can probably choose species from a wider geographical range then your local physiographic province. It doesn’t hurt and may benefit wildlife to put a Coastal Plains species in a Blue Ridge garden, if it will grow there.

My intention is to have a specimen garden, a mini-showcase of native species whose beauty is under-appreciated, so for me it’s important to find plants that aren’t cultivars.

Which brings me back to Herring Run Nursery.

I went with low hopes, but was ecstatic to find that they offered a large selection of healthy-looking actual species, though the joe-pye weed was ‘Gateway’. I left with fringetree, Carolina silverbell, scrub pine, witch hazel, spicebush, beautyberry, and about 25 different summer and autumn blooming perennials.

Now it’s possible that some of these are cultivars and just weren’t labeled as such, and not everything was perfect, but still I am really pleased to have discovered Herring Run Nursery. Please visit the website linked to above and read about Blue Water Baltimore’s mission.

interesting reading:
“From Nursery to Nature: Are native cultivars as valuable to pollinators as native species?” by Annie S. White.

*fair warning – this is the only example that’s coming to mind; as far as I know ‘Gateway’ isn’t actually a problem cultivar

Poor Joe Buttonweed


poorjoe, rough buttonweed
Diodella teres
(formerly Diodia teres)


! 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.


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.


Got Milkwort?

And now back to my finds in Serpentine Barrens Conservation Park.


purple milkwort, field milkwort
Polygala sanguinea

This intriguing small annual grows in moist to dry soils in sunny or partly shady sites. It’s often unbranched, with slender leaves and a tight raceme of flowers that is so dense it appears at first to be a single flower.

In Maryland purple milkwort is found in parts of the Coastal Plain, Piedmont, and Appalachian Plateau. It’s also fairly widespread in eastern North America, occurring in Quebec and Ontario, New England, the mid-Atlantic, the midwest, some parts of the deep South, and into the eastern parts of the Great Plains. There are no conservation issues.


There are about three dozen species of Polygala in various parts of the US, most with rather limited ranges.  P. sanguinea is one of the most widespread. Thirteen of these species are in Maryland, most of them in the coastal plain.

The genus name Polygala is from two Greek words meaning “many” and “milk” – there was a belief that cows grazing on pasture with Polygala species would produce more milk. Probably that’s the reason for the common name “milkwort”, too. (“Wort” is a Middle English word meaning “plant”.) The specific epithet sanguinea is a reference to blood, but I’m not sure why; possibly because of the color of the flowers?