There are several groups of Cardamine species in NJ.
Most common are the weeds of lawns and disturbed areas, the bittercresses (hairy, narrow-leaved, and nursery)
Next are the woodland spring ephemerals, the toothworts, of which by far the most common is cut leaved toothwort.
Finally there are the much larger wetland meadow species, cuckoo flower and bulbous bittercress.
There are a number of very rare species that are similar to each of these and which ought to be present in NJ.
Hairy Bittercress: small plant with lots of small leaflets always with a basal rosette of many leaves when it is flowering. The end leaflet is round and somewhat lobed. The fruit are held close to the stem, facing upward, NOT spreading at a 45 degree angle. Flowers extremely early in spring and in late winter, and continues for many months. Rosette is present all winter. The stems of the basal leaves are hairy, and the leaves have up to 4 pairs of leaflets.
Narrow-Leaved Bittercress: small plant with lots of small, narrow leaflets in a basal rosette and on the flowerstalk. Flowers are tiny and greenish, with minute petals that fall quickly. This plant flowers much later than hairy bittercress, in late spring. Basal rosette is present in winter. Up to 9 pairs of leaflets on the stem leaves.
Nursery Bittercress: very similar to hairy bittercress, but with somewhat wider and more lobed end leaflet, more likely to bloom in the fall, holds fruit at about a 45 degree angle from the stalk. It will have basal leaves present when flowering
Pennsylvania Bittercress: very similar to hairy bittercress, but without any basal leaves when flowering, and with fruit held at a 45 degree angle to the stem. often grows in water. Stems are thicker and whole plant somewhat succulent. leaves and leaflets tend to be decurrant (extending downward) on the stems
Wavy Bittercress: flowers are similar to hairy bittercress, much larger petals than narrow-leaved. Leaves intermediate between narrow-leaved and hairy. fruit nearly at a 90 degree angle to the stem. leaflets tend to be fairly broad. up to 6 pairs of leaflets.
Sand Bittercress: flowers are similar to hairy bittercress. Leaves are also similar, but with smaller leaflets and very large numbers of leaflets. The fruit is held away from the stem at the base, then curved upward. Flower stems are hairy, leaf stems are not. leaflets very narrow
Note: If you see a plant that looks much like these but has unlobed basal leaves it's probably Arabdopsis thalani, mouse ear cress. Other possible species are smooth rockcress and lyre leaved rockcress. The rockcresses have entire leaves (but often lobed) and flower clusters all along an inch or more of the stem. Also note that Lepidium species, shepherd's purse, and pennycresses look similar but none have elongated fruit.
Cut-Leaved Toothwort: all leaves, both on the ground and on the stem, with very narrow lobes
Two-Leaved Toothwort: all leaves both on the ground and on the stem, broad, toothed or with rounded lobes, generally with three main lobes to the leaf, not at all narrowed.
Slender Toothwort: significant contrast between broad lobed leaves on ground and small, very narrowly lobed leaves on the stem. If the basal leaves are absent difficult to tell from the vastly more common cut-leaved. If it has not flowered yet, it has sharper teeth, but is otherwise hard to tell from two-leaved.
Large Toothwort: supposedly present but I've never seen anyone find it. similar to two leaved but the central lobe or leaflet of the leaves is narrow, not as broad as on two-leaved, still broader than cut-leaved.
Note: wood anemone (Anemenoides nemerosa) looks a little like these but with single large flowers. Rue anemone is somewhat simliar, but with small, round leaflets in a whorl under the flowers. dwarf ginseng (Panax trifolius) is somewhat similar but always with three leaves (of 3 or 5 leaflets) in a whorl and flowers in a tight whorl as well. Starflower (Lysimachia borealis) has simple leaves in a whorl below generally a single flower.
Cuckooflower: this much larger plant has flowers each about the size of a fingernail or larger. Usually they have a pink tinge but not always. The plants are about knee high. The stem leaves of cuckooflower have lots of tiny, narrow leaflets in pairs
Bulbous Cress: this is similar to Cuckooflower, though the flowers tend to be droopier and not at all pink. The stem leaves are very distinctive: wedge shaped with a few teeth, but entire, not divided as in cuckooflower. stem with appressed hairs. This grows in very wet open areas.
Purple Cress: much less common, similar to bulbous cress but with drooping purplish flowers and stem hairy or smooth but not with appressed hairs.
White Cuckooflower should not be present in NJ but is in the Hudson Valley and is very like cuckooflower but white or yellowish never pinkish.
Note that rockcresses (smooth, lyreleaved) look a lot like these (especially like bulbous cress) but have entire basal leaves (bulbous cress has a large terminal lobe and a few lateral lobes). The extremely rare American (or round leaved) bittercress looks similar to cuckooflower but is only a few inches tall and creeping, without the divided stem leaves.
