Purple Flowering Raspberry is a deciduous shrub, that may reach to 5 feet in hight but usually rambles about with the cane-like stems spreading 6 to 12 feet wide.
The stems, or branches, are green initially with fine bristly glandular hair, turning woody with age and dropping the hair. The bark on older stems is light brown and peels easily into papery strips. New canes are thorn-less but with much bristly hair.
The leaves are alternate, large - 5 to 10 inches long - widely spaced on the stems, with 5 lobes usually (sometimes 3 to 7) and they resemble large Maple leaves. The lobe margins have coarse teeth. The underside of the leaf and the stalk have fine hair.
The inflorescence is a loosely branched terminal panicle, the branches of which, the flower stalks and the flower buds all covered with glandular hair making it all sticky to the touch.
The flowers are fragrant, 1 to 2 inches wide with 5 rounded rose-purple petals that overlap. The center of the flower is a mass of stamens with yellow anthers. The stamens surround a central yellowish-green receptacle which is hidden by the anthers until the petals fully expand and spread outward. The green calyx has lobes that are tipped with a long green slender appendage.
Fruit: Fertile flowers produce a raspberry like structure consisting of a domed shape of small drupes, turning red at maturity. They are said by some references to be dry and without taste and by other references to be edible, tart, with good flavor but extremely seedy.
Habitat: Purple Flowering Raspberry grows in well drained soils with medium moisture content. It does best in sun but tolerates shade well. It suckers and forms thickets and can be an aggressive spreader.
Names: The genus Rubus is the Latin name for the brambles - raspberries, blackberries, etc. The species odoratus is Latin for 'fragrant' as in the fragrant flowers. The plant author name 'L.' is for Carl Linnaeus (1707-1778), Swedish botanist and the developer of the binomial nomenclature of modern taxonomy.
Comparisons: The most likely confusing species would be Thimbleberry, Rubus parviflorus, but there the flowers are white.
Above: 1st photo - The inflorescence is a loosely branched terminal panicle. 2nd photo - In the center of the overlapping petals is a yellow-green receptacle surrounded by a mass of stamens with yellow anthers.
Below: 1st photo - All buds, and flower stalks have fine glandular hairs. 2nd photo - The calyx also has glandular hair and note the long appendages on each lobe.
Below: 1st photo - Green stems also have glandular hair. 2nd photo - The underside of the leaf has many fine hair on the veins and ribs.
Below: 1st photo - Bark on old stems becomes light brown, peeling off in papery strips. 2nd photo - The palmate leaf resembles a maple leaf.
Notes: Purple Flowering Raspberry is not native to Minnesota but was first brought to the Garden by Eloise Butler in 1908. In the summer of that year she returned to the East Coast to visit her sister Cora Pease and she returned by train via the northern route through Ontario. Outside of the town of Mackey the train either derailed or suffered some other major problem and the passengers had to wait for repairs. While waiting Eloise went 'botanizing' and came back with this plant which she planted in the Garden on Sept. 5th noting the source as "from vicinity of Mackey Ontario." We don't know how long it lasted as by the time of Martha Crone's 1951 census it was gone.
R. odoratus is native the the eastern part of on North America, not west of Ontario or Illinois. It is normally grown as an ornamental and survives quite well in Minnesota.
These other examples of Rubus are or have been in the Garden: Wild Red Raspberry, R. idaeus; Thimbleberry, R. parviflorus; Dewberry, R. flagellaris; Black Raspberry, R. occidentalis, and Blackberry, R. allegheniensis.
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"