They make the best bonsai subjects. This is true whether choosing plants found naturally or ones in a nursery. Native New Jersey trees that make good bonsai are the Eastern white cedar, found in many areas of south Jersey. Swamp maple also works well, and grows almost anywhere in the state, even along roadways where they are constantly cut down by the road departments. Eastern red cedars are particularly common in the shore area.
Pitch pines are good, but they are harder to find.
As with any collected plant material, however, potential bonsai subjects should never be taken from protected areas or from properties without the owner's permission. Good places to look for likely subjects are on a slope or on a bare hill. Best season for finding native plants is early spring, when new buds are beginning and roots are still somewhat dormant and can be safely cut and dug up. A good root ball, perhaps a third in diameter than the height of the tree, should come with the plant. Bigger trees should be put in a big pot for a couple of years, then transplanted to a smaller container, and then finally into the bonsai pot itself, a training process that gradually root prunes the plant, enabling the dwarfing process.