Rubus parvifolius (Japanese Raspberry)
|Also known as:||Japanese Bramble, Australian Raspberry, Australian Bramble, Small-leaf Bramble|
|Life cycle:||perennial woody|
|Habitat:||part shade, sun; disturbed soils; open woods, woodland edges, roadsides|
|Bloom season:||June - July|
|Plant height:||4 to 24 inches|
|Wetland Indicator Status:||none|
|MN county distribution (click map to enlarge):|
|National distribution (click map to enlarge):|
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Two to several stalked flowers in a loose cluster at the tip of 1-year-old stems, usually with one to a few flowers in the upper leaf axils. Flowers are rose-pink to red to purplish, 1/3 to ½ inch across with 5 erect, spoon-shaped petals that drop off soon after pollination. In the center is a cluster of many styles surrounded by a ring of stamens.
The 5 sepals are broadly triangular, longer than the petals, widely spreading or curving down (recurved), whitish on the inner surface, the outer surface pale green and moderately to densely hairy with scattered soft, slender bristles. Flower stalks are up to 1 1/3 inch long, covered in short hairs with scattered stiff, broad-based prickles.
Leaves and stems:
Leaves are alternate and compound, mostly with 3 leaflets on flowering stems and pinnately compound in 3s or 5s on non-flowering stems. Leaflets are egg- to fan- to diamond-shaped, often with 2 or 3 shallow lobes, mostly rounded at the tip and wedge-shaped at the base. The terminal leaflet is stalked, up to 2½ inches long, a little more or less as wide; lateral leaflets are stalkless or nearly so, smaller than the terminal leaflet and mostly longer than wide. Edges are single or double toothed, the upper surface medium to bright green and sparsely hairy, the lower surface whitish from dense, matted hairs.
Leaf stalks are sparsely to moderately short-hairy with scattered stiff, curved, broad-based prickles. Near the base of the compound leaf stalk is a pair of appendages (stipules), each up to ½ inch long, linear and hairy. Both non-flowering first-year canes (primocanes) and second-year flowering canes (floricanes) are green to purplish, sparsely to moderately hairy with scattered stiff, curved prickles. Canes are prostrate to ascending, sometimes climbing over other vegetation, and die before the third year but prostrate stems can root at the nodes and arching stems that touch the ground can also reroot and start new shoots.
Japanese Raspberry is a new introduction to Minnesota, first discovered in Stillwater in 2017 but not identified until 2019, after Jason Husveth noticed an odd-looking Rubus while collecting specimens for his sedge identification workshop. He subsequently resurveyed the vicinity, including the 2017 sighting, and found it much more widespread than he initially thought, with scattered dense patches in a wooded natural area as well as along roadsides in adjacent residential neighborhoods. The story is it had been quietly spreading from one of these residences for at least 25 years. The full extent has yet to be determined. Native to Australia and eastern Asia, it is invasive in savanna and prairie habitats according to Iowa State University, who notes its vigorous growth is difficult to control. It is tolerant of both full sun and nearly full shade. This species appears on several invasive species lists. We hope someone will eradicate the Stillwater populations before it spreads any more.
Japanese Raspberry should be easily recognized by the relatively short and sprawling stature, leaves with 3 or 5 leaflets that are generally rounded at the tip and whitish on the underside, stems that are hairy (without glands) and sparsely to moderately prickly, rose-pink to red-purple flowers, and small, round, bright red fruits. When we visited the site to photograph the plants, what immediately caught our eye were the bright green leaves—they really stood out against the darker green of surrounding vegetation, at least they did in early July. At least one cultivar, with yellow leaves, is available in the nursery trade.
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- Japanese Raspberry plant
- Japanese Raspberry with Wild Strawberry
- Japanese Raspberry with native Red Raspberry
- primocanes (background) and floricanes (foreground)
- a dense thicket of Japanese Raspberry
- leaflet undersides are white from matted hairs
- flowers arising from the upper leaf axils
Photos by K. Chayka and Peter M. Dziuk taken in Stillwater, Washington County. Fruit photo in the public domain, via Wikimedia Commons.
Have you seen this plant in Minnesota, or have any other comments about it?