Flora Pittsburghensis.

Cruciferae (Brassicaceae).

Sweet Alyssum (Lobularia maritima). A popular bedding plant that liberally seeds itself. When seeds get washed downhill, they lodge in sidewalk cracks, where they’re quite happy to grow and bloom all summer and well into fall, producing more seeds to lodge in sidewalk cracks, and making the garden Alyssum one of our more common urban weeds.

Field Pennycress (Thlaspi arvense). An unimposing little weed, but it delights children by producing round, flat seedpods that look like coins. The lesson to be learned here is that adults do not judge plants as children do, and perhaps children have a better sense of what is valuable than adults have. This plant grew in a meadow near Cranberry, where it was blooming and already seeding in the middle of June.


Charlock (Sinapis arvensis). Formerly placed in the genus Brassica, and also formerly called Brassica kaber. A common weed along roadsides and in fields. It has the typical four-petaled mustard flowers in the typical mustard-yellow color, but the larger flowers easily distinguish it from the other wild mustards.


Garlic Mustard (Alliaria petiolata). An invasive weed that came from Europe because it is a tasty and useful vegetable. It is much hated by wildflower connoisseurs, who accuse it of crowding out the natives in spring. The best thing to do with it is probably to eat it.

Tumble Mustard (Sisymbrium altissimum). Not common, but locally abundant. This is a summer-blooming mustard with small yellow flowers; tall when it’s allowed to grow, but it will bloom short in a mowed lawn. When the (annual) plant is finished, it dries up and detaches from its roots, tumbling along the ground. Unlike a tumbleweed, Tumble Mustard is well and truly dead when it tumbles, but while the corpse travels it flings its seeds everywhere.

Dame’s Rocket (Hesperis matronalis). Pittsburghers usually call it “phlox,” or—as we have heard a Pittsburgher say—“some sort of phlock.” But this ubiquitous late-spring flower is really a member of the mustard or crucifer family, as you can tell by the four-petaled flowers (real Phlox flowers have five petals). It came from Europe as a garden flower and quickly made itself at home. It would be hard to conjure up any inhospitable feelings toward this welcome guest, whose bright flowers decorate roadsides and back yards everywhere. Each colony blooms in a mixture of colors from deep magenta to white, and many plants grow flowers with splashes or stripes of contrasting colors.


Watercress (Nasturtium officinale). Watercress likes to grow with its feet in the edge of a lazy stream. The main blooming season is in the spring, but the cool weather of fall seems to give the plants their second wind, and our picture comes from a colony that was blooming profusely in late October.



Broad-Leaf Toothwort (Cardamine diphylla). Just as the Cut-Leaf Toothworts (C. concatenata) are winding down, the Broadleaf Toothworts open up. They are not as common as the Cut-Leaf Toothworts, but they like the same wooded hillsides, especially in stream valleys. Broad-Leaf Toothwort is easily distinguished by its two leaves with three broad leaflets each (C. concatenata has three leaves with very narrow lobes).

Cut-Leaf Toothwort (Cardamine concatenata). Cut-Leaf Toothworts are quite variable. They all have four-petaled white to slightly pink flowers and three finely cut leaves, but different populations are notably distinct in form, with flowers and leaves varying over a wide range.

Hairy Bittercress (Cardamine hirsuta). Depending on your point of view, this is either an invasive weed or a cheery harbinger of spring. It comes from Europe, and it makes itself at home in our lawns, where it politely refuses to exceed the height of the grass around it. There are people who eat it as a salad herb, so it can’t be all bad. It’s one of the first things to bloom in the spring, appearing along with the crocuses and persisting through daffodil season.

Spring Cress (Cardamine bulbosa). A relative of the Toothworts (which most botanists now also place in the genus Cardamine), this pretty little flower seems to like damp locations. This one was growing in a damp open woods in Bird Park in Mount Lebanon, where it was blooming in early May. The round leaves (changing to long and narrow as they go up the stem) distinguish this from other common species of Cardamine in our area.