Look at the leaves of the plant in question. To identify it as a berry, rose or briar, leaf color, shape and growth habit should be observed. Wild roses possess leaves that are oval and jagged and grow at alternating points along the stem. Blackberry leaves appear similar, but may be larger and grow in leaflets of three to five. Greenbrier has large, smooth glossy leaves with tendrils appearing at the base of each leaf stalk.
Note the canes, or stems of the plant. Roses have red or gray thorny stems, and the bark on the main stem splits to reveal the white wood beneath. Blackberry canes are tall and curved and appear green, red or purple and covered with straight or curved thorns. Greenbrier usually has stout green stems also covered with black or green thorns, some of them up to 1/4 inch long.
Observe the flowers of the plant. Berry bushes and wild roses have similar five-petaled flowers with fine hair-like stamens in the centers. Berry flowers are pink or white. Wild roses may be pink, white, yellow or red. Being closely related, the flowers appear very similar to one another, with wild roses sometimes being more fragrant. Greenbrier shows no flowers.
Look for fruit in the late summer on all bushes. While blackberries are easily recognizable to most, wild roses produce “hips” which are usually red to reddish in color, one for each flower. The seeds are housed within and enjoyed by birds throughout the winter. Greenbrier produces small round berries that ripen to a deep blue or purple and are also relished by birds and wildlife.
Notice the growth habit of the plant in question. Roses and blackberries form large, sprawling thickets. Roses also creep with a vining habit, and may use a fence or tree as a support. Blackberries arching canes create shelter in the form of thickets for wildlife. Greenbrier uses its tendrils to climb high into trees, and spreads above ground.