Rubus allegheniensis

Common blackberry canes produce leaves and actively grow in their first year (primocanes); in their second year, they switch to producing flowers and fruit (floricanes). Second-year canes produce cylindrical racemes (up to 8.5 feet long) on the tips of short lateral shoots, longer than wide, with about a dozen flowers; the peduncles and pedicels of the raceme are covered with conspicuous glandular-tipped hairs. Each flower is 1-2″ wide, has five green, pointed, triangular sepals with a tail-like extension, densely covered with glandular and non-glandular hairs; five white, rounded, wrinkled petals; 20-100 creamy stamens with white or yellow anthers; and a green cluster of numerous (100+) slender styles. After fertilization, the central cluster of styles enlarges to form a typical blackberry (drupe) 3/4″ long and a bit less than half as wide, initially white or green but turning red-black when mature. The fruit is popular with most birds and mammals (including humans), who subsequently disperse the seeds in their droppings. Like most blackberries, common blackberry can be quite aggressive, forming spreading colonies via vegetative propagation. The thin narrow “tail” at the tip of the sepals is common to all the Rubus sp. in Jackson Park. The glandular hairs on the peduncles and pedicels, leaflets at least twice as long as wide, and trifoliate leaves on canes with flowers help distinguish common blackberry from other Illinois species. Pennsylvania blackberry’s inflorescences and flowers are often partly obscured by leafy bracts; common blackberry’s inflorescences and flowers are rarely obscured. In Pennsylvania blackberry, the stipules associated with the flower pedicels sometimes are replaced by leafy bracts; this never occurs in common blackberry. The terminal leaflets of Pennsylvania raspberry are never more than twice as long as they are wide; the terminal leaflets of common blackberry are at least twice as long as wide. The petals of Pennsylvania blackberry are oblong, widest near the base, the petals of common blackberry are rounded, widest about halfway along the petal.

Common blackberry is a native blackberry, immediately recognizable as a blackberry but not so easily identified to species. It is a woody shrub whose canes are initially erect (indeed, often strikingly vertical), but often bend over, sometimes to the extent that they contact (and re-root in) the ground. The canes reach lengths of 3-8 feet. They are reddish-brown with stout straight or slightly curved, very sharp prickles except where new growth is recent (where the cane is green), and with strong vertical grooves creating an angled appearance. The leaves are alternate, usually trifoliate (on the flower-bearing canes), less often palmately compound with five leaflets (usually restricted to the first-year canes), with long petioles; leaflets are up to 4″ long and less than half as wide, ovate with coarsely double-serrated margins, and with velvety-hairy undersides. Half-inch-long lance-like stipules flank the base of the leaf petiole. Canes produce leaves and actively grow in their first year (primocanes); in their second year, they switch to producing flowers and fruit (floricanes). Second-year canes produce cylindrical racemes (up to 8.5 feet long) on the tips of short lateral shoots, longer than wide, with about a dozen flowers; the peduncles and pedicels of the raceme are covered with conspicuous glandular-tipped hairs. The glandular hairs on the peduncles and pedicels, leaflets at least twice as long as wide, and trifoliate leaves on canes with flowers help distinguish common blackberry from other Illinois species. Pennsylvania blackberry’s inflorescences and flowers are often partly obscured by leafy bracts; common blackberry’s inflorescences and flowers are rarely obscured. In Pennsylvania blackberry, the stipules associated with the flower pedicels sometimes are replaced by leafy bracts; this never occurs in common blackberry. The terminal leaflets of Pennsylvania raspberry are never more than twice as long as they are wide; the terminal leaflets of common blackberry are at least twice as long as wide. The petals of Pennsylvania blackberry are oblong, widest near the base, the petals of common blackberry are rounded, widest about halfway along the petal.

Common blackberry is a native blackberry, immediately recognizable as a blackberry but not so easily identified to species. It is a woody shrub whose canes are initially erect (indeed, often strikingly vertical), but often bend over, sometimes to the extent that they contact (and re-root in) the ground. The canes reach lengths of 3-8 feet long. They are reddish-brown with stout straight or slightly curved, very sharp prickles except where new growth is recent (where the cane is green), and with strong vertical grooves creating an angled appearance. The leaves are alternate, usually trifoliate (on the flower-bearing canes), less often palmately compound with five leaflets (usually restricted to the first-year canes), with long petioles; leaflets are up to 4″ long and less than half as wide, ovate with coarsely double-serrated margins, and with velvety-hairy undersides. Half-inch-long lance-like stipules flank the base of the leaf petiole. Canes produce leaves and actively grow in their first year (primocanes); in their second year, they switch to producing flowers and fruit (floricanes). Second-year canes produce cylindrical racemes (up to 8.5 feet long) on the tips of short lateral shoots, longer than wide, with about a dozen flowers; the peduncles and pedicels of the raceme are covered with conspicuous glandular-tipped hairs. Each flower is 1-2″ wide, has five green, pointed, triangular sepals with a tail-like extension, densely covered with glandular and non-glandular hairs; five white, rounded, wrinkled petals; 20-100 creamy stamens with white or yellow anthers; and a green cluster of numerous (100+) slender styles. After fertilization, the central cluster of styles enlarges to form a typical blackberry (drupe) 3/4″ long and a bit less than half as wide, initially white or green but turning red-black when mature. The fruit is popular with most birds and mammals (including humans), who subsequently disperse the seeds. Like most blackberries, common blackberry can be quite aggressive, forming spreading colonies via vegetative propagation. The thin narrow “tail” at the tip of the sepals is common to all the Rubus sp. in Jackson Park. The glandular hairs on the peduncles and pedicels, leaflets at least twice as long as wide, and trifoliate leaves on canes with flowers help distinguish common blackberry from other Illinois species. Pennsylvania blackberry’s inflorescences and flowers are often partly obscured by leafy bracts; common blackberry’s inflorescences and flowers are rarely obscured. In Pennsylvania blackberry, the stipules associated with the flower pedicels sometimes are replaced by leafy bracts; this never occurs in common blackberry. The terminal leaflets of Pennsylvania raspberry are never more than twice as long as they are wide; the terminal leaflets of common blackberry are at least twice as long as wide. The petals of Pennsylvania blackberry are oblong, widest near the base, the petals of common blackberry are rounded, widest about halfway along the petal.