Tall
Ironweed (Vernonia gigantea). No
photograph can convey the vivid purple color of
ironweed, one of our most spectacular late-summer
flowers. A field of mixed ironweed and goldenrod is a
sight not easily forgotten. Two species are common in
our area, and they hybridize; Tall Ironweed is, as its
name implies, taller than New York Ironweed (Vernonia
noveboracensis), but otherwise very similar.
Tall Thoroughwort (Eupatorium
altissimum). Long stands of this dusty
white thoroughwort line our highways. The narrow
grey-green three-ribbed leaves (sometimes there
are five ribs) are distinctive, and the mounds of
white flowers are very attractive to honeybees.
Hollow Joe-Pye-Weed (Eutrochium fistulosum). This beautiful and elegantly constructed plant, also known as Trumpetweed, bears domes of dusty mauve flower heads on towers of whorled leaves, usually five to seven in a whorl. The plants can easily grow to seven feet or more. They prefer a damp environment, and are often seen in the soggier parts of roadsides and fields.
White
Snakeroot (Ageratina altissima). One of
our most decorative late-summer and autumn flowers,
White Snakeroot lights up the edge of the woods and
can form a perfect ornamental border around a field.
The flowers are pure white, with projecting white
stamens, As a member of the Composite family, this
species is especially interesting for the way the
individual little five-parted flowers are easily
distinguishable in the heads. It’s a good plant for
demonstrating the construction of a Composite flower
to children.
Lance-Leaved Goldenrod (Euthamia graminifolia). Also called Bushy Goldenrod, Grass-Leaved Goldenrod, Fragrant Goldenrod, and probably any number of other names. This is one of the class of flat-topped goldenrods that most botanists now put in their own genus, Euthamia, rather than lumping them in with Solidago the way older botanists did. Identification is easy, because this is the only flat-topped goldenrod reported to grow in the Pittsburgh area.
Wreath
Goldenrod (Solidago caesia). A more
contemplative sort of goldenrod. Its showier cousins
brighten fields and meadows, but the Wreath or
Blue-Stemmed Goldenrod is happiest in an open
woodland, thriving in deeper shade than almost any
other other fall flower. Its arched stems of golden
flowers have a restrained elegance that seems
appropriate to the dim religious light of the woods.
Zigzag
Goldenrod (Solidago flexicaulis). A
distinctive goldenrod that likes clearings in the
woods or the banks of a stream. Its broad rounded
toothy leaves are distinctive, and it takes its common
name from the angled stems, which zigzag from one leaf
to the next. (“Zigzag” is a technical term in botany.)
The flowers grow in a wand at the top of the stem,
with more flowers filling in the leaf axils.
Aster
Fleabane (Erigeron annuus). A
very common but always delightful weed; its multiple
heads of cheery daisy-like flowers bear large numbers
of delicate white rays. It can be found on roadsides,
at the edges of parking lots, in vacant lots, or in
lawns given half a chance. Its peak blooming season is
in June.
Seriocarpus
Antennaria
Anaphalis
Gnaphalium
Bellis
Elecampane
(Inula helenium). Elecampane is a tall
and striking flower, imported from Europe,
recognizable by its thick stems of sunflower-like
flower heads with narrow, shaggy rays. It is not
particularly common around here, but abundant where it
does take up residence.
Iva
Ragweed (Ambrosia artemisiifolia).
The bane of allergy-sufferers everywhere, Common
Ragweed is wind-pollinated: instead of large
attractive flower heads, it relies on myriad small
pollen-dispensers. The plant in full bloom passes
nearly unnoticed, even in large drifts. It grows
everywhere—in cracks in the pavement, in vacant lots,
at the edge of a yard, in the middle of your garden.
Giant Ragweed (Ambrosia trifida).
A heaping helping of ragweed, easily growing to 9 feet
(3 m) if it likes the location (Gray says to 6 m or 18
feet), and letting loose a raging torrent of
allergenic pollen in early September. The harmless and
beautiful goldenrods that bloom at the same time often
take the blame for hay fever, but this huge yet
somehow inconspicuous weed, and its even more common
little cousin A. artemisiifolia, are the
real culprits.
Xanthium
Silphium
Heliopsis
Rudbeckia
Ratibida
Helianthus
Wingstem
(Verbesina alternifolia). A tall and
cheerful native flower that may be abundant in some
areas and absent in others. It likes the edge of the
woods, and seems to be happiest on a hillside. The
disk florets are unusually large, arranged
pincushion-fashion. The drooping rays are irregular
and rather sloppy; there may be only two of them, or
up to eight, and they be be significantly different in
size and shape.
Coreopsis
Spanish
Needles (Bidens bipinnata). This is one
of those flowers that reward a close look. The flowers
are like tiny marigolds, and indeed they’re sometimes
called bur-marigolds. The seeds, long and narrow like
marigold seeds, have hooks that stick in animal fur or
people’s clothes.
Pittsburgh Pest (Galinsoga parviflora).
Obviously this is not known as Pittsburgh Pest
everywhere in its nearly global range, but the name
seems to be well established here, and it is
frequently used elsewhere in the United States. The
flowers are like tiny five-rayed daisies; the plant is
low and hairy, and can grow from any crack in the
pavement. It is very much an urban weed, ubiquitous in
the city of Pittsburgh, but much rarer in the near
suburbs, and unknown in all the other counties of the
metropolitan area but one (Washington County).
Sneezeweed
(Helenium autumnale). Sneezeweed is an
attractive composite flower with distinctively notched
rays that make it easy to identify. (A similar
species, Purple-Headed Sneezeweed, Helenium flexuosum,
has been introduced in a few locations; it is easy to
distinguish by the dark brownish button in the
center.) The plant likes damp areas.
Yarrow (Achillea millefolium).
Also called Milfoil, “thousand-leaf,” from the finely
divided leaves. A European import that has become a
common wildflower all over the East. Still a popular
garden flower; in recent years many colors have been
bred, but the wild ones are almost always white, or
more rarely pink. The blooming season is long, from
June through October.
Chrysanthemum
Ox-Eye Daisy (Leucanthemum vulgare).
Considered a noxious weed in some parts, but around
here it seldom takes over enthusiastically enough to
be a problem. This is the flower commonly known as
“daisy” to Americans, and it is more beloved than
hated almost everywhere it grows. It holds its daisies
up proudly on long stems perfect for cutting. In most
of our older references, this species is placed in the
genus Chrysanthemum.
Tansy
(Tanacetum vulgare). A rayless
Composite: that is, a flower head with only disc
flowers and no rays, like a daisy with no “petals.”
The yellow button-like discs and lacy fernlike foliage
are distinctive. Tansy came over here as a garden
staple, but it has made itself at home. It is never
abundant enough in Pittsburgh to qualify as a pest; it
is only a pleasant visitor popping up in unexpected
places.
Artemisia
Coltsfoot (Tussilago farfara). Coltsfoot is one of our earlier spring flowers. The cheery and shaggy yellow flower heads top a short stalk that pops straight out of the ground; there are no leaves until later on. The plant’s favorite habitat seems to be a damp hillside at the edge of the woods, often beside a street or highway. Coltsfoot was, as its generic name suggests, a popular cough remedy; but it has been known to cause serious liver damage, so it’s not as popular as it used to be.
Erechtites
Cacalia
Groundsel (Senecio vulgaris).
This ubiquitous weed is found in temperate latitudes
throughout the world. The tight little flower heads
never open up any wider than what you see here. This
plant has one of the longest blooming seasons of all
our weeds: on this page we have pictures from late
June and from early February.
Golden Ragwort Packera aurea.
Like bright yellow asters, these cheery composite
flowers come out in time for Mayday. There is
nothing else like them blooming in the spring
around here, so they are easy to recognize.
Arctium
Bull Thistle (Cirsium vulgare).
This is the big, spiny thistle that always pops up
just where you don’t want a thistle. On the other
hand, goldfinches love the seeds so much that it’s
hard to imagine how the birds survived before
Europeans introduced the plant to this continent.
Architecturally, the whole plant is very elegant, and
the flower heads are superbly artistic, with a tuft of
pure magenta erupting from a prickly urn. The flowers
begin in July and continue on and off till frost.
Centaurea
Chicory
(Cichorium intybus). The distinctive
sky-blue flowers make Chicory unmistakable. Varieties
of Chicory are used as salad greens and as a coffee
substitute or additive. It grows along roadsides,
often in the company of Queen Anne’s Lace (Daucus
carota), and seems especially happy in a crack
in the asphalt at the edge of a parking lot.
Krigia
Hypochoeris
Tragopogon
Dandelion
(Taraxacum officinale). Dandelions can
bloom almost any time of the year; they prefer the
cool weather of spring, but will bloom sporadically
through the summer, with another burst of enthusiasm
in the fall, and occasional appearances even in the
winter if we have a warm spell. No matter how much
suburbanites hate dandelions in their lawns, anyone
with any aesthetic sense must grudgingly admit that
the common dandelion is one of our most perfectly
beautiful flowers.
Sonchus
Lactuca
Prenanthes
Hieracium