Gleditsia triacanthos
Senna hebecarpa
Partridge Pea (Chamaecrista fasciculata). A delicate-looking plant with Mimosa-like leaves that quickly colonizes recently disturbed or burned areas. The cheery yellow flowers can keep coming for months. They are unlike typical pea flowers in being open rather than having the lower petals fused into a keel.
Redbud (Cercis canadensis). A
common tree in the forests around Pittsburgh, and also
a favorite ornamental in urban and suburban yards. The
bright magenta flowers, instead of coming at the ends
of branches, pop right out of the wood. They bloom in
late April.
Red
Clover (Trifolium pratense). This
ubiquitous European import grows almost anywhere the
grass isn’t mowed too frequently. It came to America
as a pasture crop, and soon found that it really liked
our open spaces. The leaves usually show a chevron
pattern, which distinguishes it from the similar but
rarer Alsike Clover (Trifolium hybridum). Red
Clover keeps blooming throughout the season.
White Clover (Trifolium repens).
It grows in every lawn, but unless you are obsessive
about your grass, there is little to object to in this
little weed. It is very easy to mow, it never grows
very tall even without mowing, and it does the soil
good. The flowers are frequently tinged with pink, and
of course an occasional leaf grows with four leaflets.
Alsike Clover (Trifolium hybridum).
Red Clover (T. pratense) is more common and
very similar, and grows in most of the same places.
The best way to tell the difference is by the leaves,
which in Red Clover usually (but not always) show a
chevron pattern but are unmarked in Alsike Clover; and
by the color of the flowers, which in Alsike Clover is
less magenta and more pale rosy pink, with young white
flowers in the center of the head. In fact, it does
look like something halfway between Red Clover and
White Clover (T. repens), which may account
for the specific name hybridus for a plant
that is not a hybrid.
White Sweet Clover (Melilotus albus).
Imported for fodder, White Sweet Clover and the
similar yellow species M. officinalis
(almost indistinguishable until the flowers appear)
have made themselves at home here to such an extent
that some regard them as pests. Nevertheless, as
nitrogen-fixers that cattle like to eat, they give us
a lot in return for the inconvenience they cause us.
Yellow Sweet Clover (Melilotus
officinalis). Hard to tell from White
Sweet Clover (M. alba) until they both bloom.
When they do bloom, the yellow species reveals
sloppier habits; the flower spikes are more ragged
than the ones of M. alba, with withering
flowers retained for a long time. Nevertheless, the
delightful scent is enough to make us forget the
slight slovenliness of the presentation. Yellow Sweet
Clover grows plentifully along roadsides, and is often
one of the first plants to colonize a recently
disturbed site.
Medicago sativa
Medicago lupulina
Birdfoot Trefoil (Lotus corniculatus).
This is a plant that seems to be adapted above all to
roadsides. It thrives in poor soil and can live
happily in gravel, and it stays short enough to laugh
at occasional mowing, though it would not survive a
mower-obsessed suburbanite’s lawn. It is certainly one
of our most decorative roadside weeds. The bright
yellow flowers reward a close look: they have thin red
stripes on the “standards,” the upper part of the
flower.
Black Locust (Robinia pseudoacacia).
This tree is ubiquitous in southwestern Pennsylvania,
so it may come as some surprise to Pittsburghers that
we live at the northern end of a native range that is
actually very small, mostly in the Appalachians and
foothills. The Black Locust has been much planted
elsewhere, however, and may easily naturalize itself.
It is in many ways an ideal urban tree: it grows fast,
tolerates city conditions with no complaints, and has
showy clusters of white pea flowers after most of the
other flowering trees have stopped blooming. It does,
however, have one serious flaw. Mature specimens are
brittle, and can easily drop large branches in storms,
crushing cars or bringing down power lines. When your
power goes out in a thunderstorm, there’s a very good
chance you have a Black Locust to blame.
Showy Tick-Trefoil (Desmodium canadense).
Tick-trefoils are mild annoyances to hikers and
walkers, but this one is such a beautiful flower that
we can easily forgive it. Like all the other
tick-trefoils, it has transformed the ordinary legume
of the pea family into a fabulously efficient
instrument of dispersal. The pod is divided into
individual segments that separate easily, and each of
them is coated with sticky adhesive hairs. As you pass
by the plant, several of those segments stick to your
clothes and ride off with you, at least until you
notice them. It may be quite a distance: since the
seedpods are sticky rather than prickly, you tend not
to notice them until you see them. Other tick-trefoils
have pretty but inconspicuous little flowers; this
one, however, has larger flowers in a dense and showy
raceme.
Lespedeza procumbens
Lespedeza violacea
Lespedeza intermedia
Lespedeza hirta
Cow Vetch (Vicia cracca). A
European import cultivated for fodder, Cow Vetch tends
to be found wherever livestock is nearby. The vines
twine through other less decorative weeds, and the
beautiful blue-purple flowers light up the edges of
fields.
Crown
Vetch (Securigera varia). Crown Vetch
is often planted to control erosion on hillsides; it
also escapes freely and makes a nuisance of itself.
But the bicolored flowers are pretty. They come in
various shades, including occasionally pure white or
lavender.
Everlasting pea (Lathyrus latifolius).
A vigorous vine that can take over whole hillsides. It
compensates us for the space it takes with a glorious
array of flowers in shades from white through deep
magenta, often with stripes or bicolor patterns. It’s
called “everlasting” because it has flowers like the
annual garden sweet pea, but it’s a perennial; thus
another common name, “Perennial Sweet Pea.”
Hog Peanut (Amphicarpaea bracteata).
A vine that twines its way through the underbrush
along creeks and streams, dangling clusters of flowers
in white, pink, or purple. These flowers produce
seeds, but the vine also grows less showy flowers near
the ground that turn into a single underground seed,
like a peanut.