Many kinds of sweet, pulpy fruits and berries, such as raspberries, gooseberries, elderberries, grapes, red haws and cherries are eaten by birds and other animals. The soft parts of the fruit are digested, but the seeds are able to pass through the intestines undamaged and be dropped, often long distances away. Gray squirrels and fox squirrels bury oak acorns and the nuts of hickory and walnut for winter food. Some are carried considerable distances away, forgotten, and start new trees. In this way uncultivated fields are slowly being reforested from nearby woodlands.
Burs are of many types.
Sticktights are the bean-like pods of the legume, tick trefoil. Spanish needles are shaped like pitchforks. The sandbur, with its stiff, barbed spines, stabs into the feet of dogs and barefoot youngsters. Burdock, cocklebur, beggar's lice and bedstraw are other common seeds that steal rides. Accidentally, or carelessly, the seeds of many undesirable plants were brought across the ocean in ships and allowed to escape and grow.