Recognized as a distinct species in the USDA 'Plants Database' https://plants.usda.gov/core/profile?symbol=RUPH2, this species is treated as a synonym of Rubus pensilvanicus Poir., in the Flora of N. America[
The genus Rubus, (especially the blackberries, which are often loosely referred to as Rubus fruticosus agg.) presents some of the most difficult taxonomic problems. This is partly due to the frequency of polyploidy; also to the frequent occurrence of hybridization; and also due to apomixis, where minor differences between plants are preserved because seedlings are genetically identical to their parent. As a result, differences of opinion on the number of species to be recognized from a given region can vary tremendously (for example, a treatment by M. L. Fernald[
] in 1950 recognized 205 species for the northern half of the eastern United States plus parts of southeastern Canada, whilst H. A. Gleason and A. Cronquist in 1991 recognized only 25)[
]. Where possible, a relatively conservative approach is taken here[
Common Name: Philadelphia Blackberry
Rubus philadelphicus is a deciduous shrub, producing each year a cluster of erect to arching, prickly, biennial stems from a woody rootstock; the plant can grow 100 - 300cm tall[
]. The stems only produce leaves, and do not flower, in their first year of growth; forming flowering branches in their second year and then dying after fruiting[
]. The plants form roots where the stem tips touch the ground, developing into dense, impenetrable clusters.
The plant is harvested from the wild for local use as a food. It has been cultivated as a food crop in the past and is probably the source of the outdated cultivar 'Lawton', at one time the leading cultivated blackberry in the USA[
Eastern N. America - Wisconsin to Vermont, south to Kentucky and North Carolina.
Thickets, borders of woods and clearings[
]. Woodlands, savannahs, prairies, fields, meadows, swamps, rock outcrops, sand dunes, sandy soil, disturbed areas, dry to wet soil; at elevations up to 1,400 metres[
|Other Uses Rating||
|Cultivation Status||Cultivated, Wild
Rubus philadelphicus is native to the temperate regions of eastern N. America, growing in hardiness zones 4 - 8.
Species in this genus are generally easily grown in a good well-drained loamy soil in sun or semi-shade[
Plants in this genus are notably susceptible to honey fungus[
Fruit - raw or cooked[
]. Good quality. The black, globose to cylindrical fruit is around 10 - 20mm in diameter[
Most, if not all, thicket-forming species of Rubus have good erosion control value. They usually grow satisfactorily on barren and infertile soils and invade and occupy eroded areas. They also establish quickly on burns, old fields, and logged areas. Forming extensive and nearly impenetrable thickets, they can provide excellent cover for wildlife as well as nesting sites for small birds. They are often natural pioneer species, paving the way for woodlands to develop, but they should only really be used within their native range in order to avoid any risks of them invading other habitats[
A purple to dull blue dye is obtained from the fruit[
Seed - requires stratification and is best sown in early autumn in a cold frame. Stored seed requires one month stratification at about 3°c and is best sown as early as possible in the year. Prick out the seedlings when they are large enough to handle and grow on in a cold frame. Plant them out into their permanent positions in late spring of the following year.
Cuttings of half-ripe wood, mid summer in a frame[
Tip layering in July. Plant out in autumn.
Division in early spring or just before leaf-fall in the autumn[