Rubus idaeus ssp. strigosus

Native

Common and widespread

Dry to moist. Forests, forest margins, woods, thickets, lake shores, meadows, roadsides. Full sun to partial shade.

Late May to early July

White petals, green sepals

3′ to 7′

This is a 3′ to 7′ tall, erect bramble that rises on multiple stems from a long, underground, perennial rhizome. It often forms dense colonies. It is the most widespread and often commonest tall blackberry in Minnesota.

A series of biennial stems are sent up from a perennial base. First year stems (primocanes) do not flower. They grow to their full height, which can be up to 7′ long and somewhat arching near the top, but in Minnesota is usually about 3′ tall and erect. They do not arch to the ground and do not root at the tips. They are initially light green, eventually turning reddish or brownish, and are sometimes covered with a whitish, waxy coating (glaucous). They are round (not grooved), and become woody, at least near the base. They have 15 to 50 or more stiff, 1 ⁄32″ to ⅛″ long, bristly hairs per centimeter (⅜″). They do not have soft hairs or broad-based prickles. When young they also have soft, gland-tipped hairs, at least near the top. Under a hand lens these hairs look like a stalk with a ball on the end.

The leaves are alternate and deciduous. Primocane leaves are palmately divided into 3 leaflets or pinnately divided into 5, rarely 7, leaflets. They are on leaf stalks that are 1⅛″ to 2⅜″ long and covered with gland-tipped hairs and stiff bristles. At the base of each leaf stalk is a small appendage (stipule) that is 3 ⁄16″ to ⅜″ long and lance-shaped, linear, or thread-like. The central stalk of the leaf is often bristly.

The terminal leaflet is egg-shaped to elliptical, occasionally 3-lobed, and is on a stalk about ⅜″ long. The larger terminal leaflets are 2⅜″ to 4⅓″ long, 1½″ to 2¾″ wide. The blade is usually rounded, sometimes heart-shaped, at the base, and tapers to a point at the tip with concave sides along the tip. There are 10 to 15 lateral veins on each side of the midvein. The upper surface is dark green and initially sparsely hairy, eventually becoming hairless. The lower surface is gray-green or silvery gray due to a dense covering of grayish hairs. The margin is toothed or doubly toothed with sharp, forward-pointing teeth. The lateral leaflets are smaller, asymmetrically egg-shaped, rounded at the base, stalkless or nearly stalkless, but otherwise similar. When 5 leaflets are present, the lower two leaflets are well separated from the upper 3 by up to 1⅛″.

Second year stems (floricanes) do not grow longer but develop side branches. The leaves are similar to primocane leaves but are divided into 3 leaflets, rarely 5. The leaflets are smaller and narrower.

The inflorescence is a dense, flat-topped or convex, often drooping cluster of 3 to 7 flowers at the ends of the stems and branches. The stalked flowers in the cluster grow upward from various points on the main stem to approximately the same horizontal plane (corymb). Sometimes there are also 1 or 2 flowers rising from upper leaf axils. The stalk of the cluster and the stalks of the individual flowers are bristly have numerous gland-tipped hairs.

The flowers are 5 ⁄16″ to ½″ across and are not showy. They are on 3 ⁄16″ to 1⅜″ long stalks that are covered with bristles and gland-tipped hairs. There are 5 green, 3 ⁄16″ to ⅜″ long sepals. They are triangular to lance-shaped, hairy, erect to spreading when in flower, eventually bent backward when in fruit. There are 5 white, elliptical, ⅛″ to ¼″ long, erect petals. The petals are shorter than the sepals. There are many stamens, all shorter than the petals. The flowers appear in late May to early July.

The fruit is a bright red, juicy, short, almost globe-shaped, ½″ to ⅝″ in diameter aggregate of multiple drupelets. It matures mid-July to late August. When picked it separates easily from its core. It is smaller but tastier than the domestic raspberry.

Allegheny blackberry (Rubus allegheniensis) leaves are palmately lobed.

American red raspberry (Rubus idaeus ssp. idaeus) is a similar European species that lacks gland-tipped hairs on first-year canes, leaf stalks, flower stalks, and calyces. The leaves are pinnately divided into 5 or 7, rarely 3, leaflets. It sometimes escapes gardens but is not naturalized.

Black raspberry (Rubus occidentalis) is a larger plant. The canes can get much longer, up to 13′. Longer canes arch to the ground and root at the tip. They have broad-based prickles and no bristles. The fruits ripen purplish-black, not red.