In August the Potomac downstream of Carderock is lined with tall flowering plants by the thousands. Halberd-leaved rose mallow (fotd 8/7) is still going strong, though starting to wane, while thin-leaf sunflower (fotd 8/19), tall coneflower, and large-flowered leafcup (come back tomorrow to read about that one) are dominating the view. And I do mean dominating, as these plants can grow to eight feet in height, and tend to form large colonies through rooting.
Flowers in the aster family (formerly known as the composite family, Compositae) are fascinating. What appear to be petals are actually individual flowers, known as rays; the central portion of the head is comprised of individual disc flowers. In some composite family flowers, like the Eupatorium species I wrote about last week, only disc flowers are present. In others, like rattlesnake weed (fotd 5/31) and hairy hawkweed (come back the day after tomorrow), there are only ray flowers.
The coneflowers (Rudbeckia and Echinacea species) are easily distinguished from the sunflowers (Helianthus species, and many others) by the reflexed ray flowers and the more-or-less spherical shape of the disc.
There are 22 species of Rudbeckia in the US, four of which are found in this area, including Maryland’s state flower, the black-eyed Susan (R. hirta). Tall coneflower is threatened in Rhode Island.
This FOTD is a little premature, as it’s still in bud, but I’m on a roll here with the Eupatoriums. This one can grow up to five feet tall, and has longer, narrow leaves than the other species I’ve written about the past few days. The inflorescence is rather flat.
This plant, also known as late boneset, is endangered in New York. Like most of its relatives, it can be found across the eastern US and into Canada.
Tomorrow, I’ll take a break from plants in the aster family – but not for long, because this is the time of year when they really dominate. As of August 13, 13% of the plants I’ve catalogued this year have been in the Asteraceae. By October that figure might be as high as 25%. Of all the plants families on this earth, only the Orchidaceae has as many species.
Yet another in the series of Eupatorium-type flowers, formerly named Eupatorium coelestinum. Note once again how similar the flowers are to the others I’ve posted about in the last few days. This plant grows up to three feet tall, and has triangular leaves with short petioles. It’s closely related to the common garden plant ageratum. Its native range is from Ontario and New York south to Florida and west to the central and southern Great Plains.
Here’s a picture showing flowers, buds, and the characteristic leaves:
Yes, another of the Eupatorium-type plants. In fact, this species was formerly named Eupatorium rugosum. It can be distinguished from the bonesets by the leaves, which have long petioles (instead of being perfoliate or sessile), and are generally cordate (heart-shaped).
The inflorescences are a little different in shape, but the individual flowers look similar to boneset and joe-pye weed flowers, at first glance, anyway.
Other common names include tall boneset, white sanicle, and richweed. At one time people believed that the roots could treat snakebites, hence the name. Actually, the plant is poisonous, and the source of “milk sickness” that killed many settlers in the early 1800s. Apparently cows don’t normally graze on white snakeroot, but they can if forage is sparse; the poison is then passed through the milk to people.
White snakeroot is found in a wide variety of moist-soil, partly-sunny habitats, from Quebec to Florida and west through the Great Plains.
UPDATE 1/11/17: I now believe these pictures to be of Godfrey’s thoroughwort, Eupatoriumgodfreyanum
Eupatorium pubescens; Asteraceae (aster family)
This species is still in the genus Eupatorium (for now), and is also known as E.rotundifolium, and by the common name roundleaf thoroughwort. Notice that the flowers are very similar in shape and size to yesterday’s FOTD. The inflorescence is flatter, though, and in most other ways the plant looks completely different:The leaves are much smaller, rounder, and sessile (joy-pye leaves have long petioles at the center and lower portions of the stem). And, the leaves are arranged in pairs on the stem instead of whorls of four. Also, as you can see from the picture above, hairy boneset likes a drier habitat, preferring rocky upland soils.
Hairy boneset is endangered in New Hampshire and New York, and possibly extirpated in Maine. Its native range is from Maine south to Florida and west to Louisiana and Arkansas.
By the way, the common name “boneset” supposedly derives from the plant’s use in treaing dengue fever (also known as breakbone fever). “Thoroughwort” comes from the perfoliate characteristic of the leaves of several of these species. (A perfoliate leaf is one in which the stem appears to pierce, or go through, the leaf.) Later this week I’ll feature a thoroughwort.