Flower:

Elongating clusters of stalked flowers at the top of the plant and the tips of branching stems. Flowers are 1/8 to ¼ inch across with 4 rounded white petals and 6 creamy white to pale yellow stamens slightly protruding from the center. The 4 sepals behind the flower are 1.3 to 2.3 mm oblong, hairless, and green to purplish.

Leaves and stems:

Leaves are compound, a leaf up to 6 inches (4 to 15 cm) long. Basal and lower stem leaves are similar, with oval to round leaflets that may have a few teeth or shallow lobes, the end leaflet largest. Basal leaves typically wither away by flowering time.

Leaflets on stem leaves become more narrow, mostly toothless or with a few shallow lobes, short-stalked to stalkless, the end leaflet distinctly broader and longer than the lateral leaflets, up to about 1 inch (1.3 to 3+ cm) long. Stems are single from the base, branched, often very leafy, sparsely hairy near the base and hairless above, green or sometimes purplish.

Fruit:

Fruit is a slender pod ¾ to 1¼ inch (1.7 to 2.7+ cm) long, erect to ascending and mostly straight.

Notes:

A similar species is Small-flowered Bittercress (Cardamine parviflora), which is a smaller, more spindly plant found in dry soil, where Pennsylvania Bittercress is found in moist to wet places. The end leaflet of Pennsylvania Bittercress is also distinctly larger than the lateral leaflets, where they are nearly the same size on Small-flowered Bittercress. Also similar is the invasive Narrow-leaf Bittercress (Cardamine impatiens), which has smaller flowers, is hairless, leaflets are all stalked, and the stem leaves have a pair of narrow lobes (auricles) at the base of the compound leaf stalk.