Rubus occidentalis

Black raspberry (Rubus occidentalis)
Scientific name	Rubus occidentalis
Common names	Black raspberry; blackcap; blackcap raspberry
Genus	Rubus
Family	Rosaceae
Order	Rosales
Native range	Eastern Canada; north-central and eastern United States
Habit	Deciduous bramble with arching canes to about 6 ft, forming thickets
Fruit	Black-purple compound drupe that separates cleanly from the receptacle
Propagation	Seed with cold stratification; tip-rooting; bare-root and container plants
Hardiness	USDA zones 4a–8b; winter lows near −28 °F
Years to fruit	About two years to establish a planting; older container plants can crop in year one

Rubus occidentalis, known as the black raspberry or blackcap, is an accepted species of bramble in the family Rosaceae, first described in 1753.^[1][2] It is native to eastern Canada and the north-central and eastern United States, recorded from Ontario, Quebec and New Brunswick across roughly thirty states, and has been introduced into parts of Europe.^[1] It grows along forest edges, roadsides and other disturbed ground, and it is a distinct crop from the red raspberry (Rubus idaeus): the canes arch strongly, the berries are smaller, seedier and more aromatic, and the ripe fruit is a black-purple compound drupe that separates cleanly from the receptacle.^[3][4]

Description

First-year canes grow erect to about 6 ft and then arch sideways and down, sometimes reaching the ground; mature plants form thickets about 6 ft tall with rapid growth, a short lifespan and vigorous resprouting, and the PLANTS record classes the growth form as thicket-forming with rapid vegetative spread.^[3][5] Young stems are green, hairless and coated with a glaucous bloom that rubs off white, then turn brown and woody and carry short, curved prickles.^[3] The alternate leaves are trifoliate with doubly serrate leaflets of about 1–3 inches.^[3]

Flowers are white and five-petaled, borne in small cymes from April to June on second-year canes.^[3][5] The fruit is a compound drupe under 1 inch long, each drupelet holding a single seed; it ripens from white through red to black-purple in June and July and detaches cleanly from the receptacle.^[3] Recorded synonyms include the homotypic Melanobatus occidentalis and Rubus tomentosus, and the heterotypic Rubus idaeus var. americanus, Rubus occidentalis var. flavobaccus (a yellow-fruited form), var. grandiflorus, var. incisus, var. japonicus and f. pallidus.^[1]

Cultivation

In North Carolina the species is common in mountain woodlands and along roadsides, and only scattered in Piedmont and coastal settings.^[3] The PLANTS record lists a minimum temperature of −28 °F, and NC State lists USDA zones 4a–8b.^[5][3] NC State profiles the species as preferring partial sun and moist, highly organic soil and as heat tolerant, with the caveat that on sunny, dry sites the fruit may not develop properly without adequate rain.^[3]

Soil and water

The PLANTS record lists a pH range of 5.2–7.5, medium moisture use, medium drought tolerance and no salinity tolerance; extension guidance for bramble plantings narrows the practical range to pH 5.8–6.5 on sandy loam with organic matter, well drained, and recommends raised beds or ridges because most brambles are susceptible to root rot.^[5][4] A central-Florida growing thread reports that raspberries there do poorly in shallow, hard limestone soil and prefer sandy, fertile ground that holds moisture but drains, with mulch helpful on shallow sites.^[6]

Sun and humidity

Cane growth is strongest in partial sun; canes fail to set fruit in deep shade, and extension guidance for bramble plantings calls for an open site with at least 6–8 hours of sun.^[3][4] The PLANTS record classes shade tolerance as medium.^[5] In hotter lowland climates, raspberries bake in direct full sun and grow better with some shading and generous water through the hotter half of the year, an observation from the same central-Florida thread rather than a species trial.^[6]

Seasonal changes

The species is deciduous with active growth in spring and summer, flowering from April to June and fruiting from June to July in its native range.^[3][5] Because the crop forms on second-year canes, a full harvest depends on the previous season's canes surviving winter. Late-spring freezes can define the season: in an Ohio cultivar trial, a freeze on 22 May 2002 killed 91% of Jewel blossoms, 81% of Bristol blossoms and 18% of Mac Black blossoms.^[7] Through fruit fill, keep moisture steady; extension guidance treats the planting as weed-free with annual pruning once established.^[3][4]

Propagation

Seed requires cold stratification, and the PLANTS record lists planting as bare root, container or sprigs while marking propagation by cuttings as No; the NC State profile, by contrast, recommends seed and stem cuttings, a conflict left as recorded.^[5][3] Growers on GrowingFruit.org rely on tip-rooting — pinning a cane tip into soil where it roots — to propagate and keep a variety going; a grower with twenty-five years of Jewel recommends tip-rooting new plants at about the five-year mark to keep the variety going long-term.^[8] Extension guidance for bramble plantings places black raspberries on a hill or low trellis about 2.5 ft apart in the row and 10 ft between rows, with trellis wire at about 40 inches, and notes that at least two years are required to establish a planting, while containerized two-year-old plants can crop in the first year.^[4] Because aphids transmit latent viruses from red raspberries to the more susceptible blackcaps, keep black raspberries separate from red plantings and from wild brambles within roughly 300 ft.^[4]

Flowering, fruiting, and harvest

White flowers open from April to June on second-year canes, and fruit ripens from June to July.^[3][5] The compound drupe is at picking stage when fully black-purple, at which point the drupelets separate cleanly from the receptacle; fruit picked earlier remains white, red or partially colored.^[3] In the Ohio trial, Bristol peaked about 21 June, Jewel about a week later, and Mac Black up to about ten days after the early types, extending the season;^[7] one grower recorded Bristol on 18 June and Jewel on 23 June in his garden, with a picking season of about three to four weeks.^[8]

Fruit and uses

The berries are sweet and slightly tart, with what the NC State profile calls excellent flavor and variable quality, the finest forms having a rich acid flavor.^[3] They are eaten fresh and cooked into toppings, fillings and jams; young spring shoots are harvested while tender, peeled and eaten raw or cooked like rhubarb, and a tea is made from the leaves or root bark.^[3] Extension nutrition notes credit raspberries generally with vitamins A and C.^[4] The black raspberry character is distinct enough that some growers describe the flavor as not particularly raspberry-like in the red-raspberry sense, even where hybrids such as Brandywine carry a black-raspberry-dominant flavor.^[6]

Cultivars and selections

Most named black raspberries are floricane types that crop once in early summer; a newer primocane-fruiting group is also sold.

Bristol, released in 1934 from Geneva, New York (Watson Prolific × Honeysweet), is early, with medium-large, firm, glossy berries and good flavor; it is a good yielder and mildew tolerant but susceptible to anthracnose.^[7][4] Jewel, released in 1973 ((Bristol × Dundee) × Dundee), is early-mid season, with large, firm berries and good flavor on a vigorous, erect, anthracnose-resistant plant that is widely adapted; it ripens about a week after Bristol.^[7][4] Mac Black is mid-late and probably the latest-producing type in Ohio, extending the picking season about ten days; in the trial year it carried the fewest blossoms and set almost no fruit while establishing.^[7][4] The extension table also lists Allen (early-mid, large berries, mild flavor), Hault (early, medium berries, good flavor) and Black Hawk (late, medium-large berries, good quality, resistant to anthracnose).^[4]

Measured differences between the named types are modest. In the single-season Ohio trial, Jewel berries averaged 2.48 g (range 0.83–5.08 g) against 1.66 g (0.82–3.42 g) for Bristol, and Bristol out-yielded Jewel 0.72 versus 0.30 quarts per plant; Brix readings ran 10.3 (Bristol), 10.1 (Jewel) and 10.4 (Mac Black), a spread far below the roughly 1.5% Brix change humans perceive, so sweetness differed little among the tested berries.^[7] Grower comparisons add vigor and longevity notes: on GrowingFruit.org, Bristol is described as far more vigorous than Jewel, sending up four to eight new primocanes against one to four, and a long-time Jewel grower reports Jewel always stingy with primocanes, one to three per clump a year, recommending tip-rooted replacements at about the five-year mark.^[8] Another grower finds Jewel berries easily three times the size of the average wild blackcap, with a rich, jammy flavor.^[9] One breeding-thread participant reports that named cultivars in his garden died out after about three to four years while a wild yellow-fruited selection from southern Ontario has thrived for ten years in the same container, apparently virus-free or asymptomatic — a single-grower report, not a general performance claim.^[10]

Primocane-fruiting black raspberries are a recent development. Niwot carries a large summer crop, but individual growers report the fall crop often fails in short-season zones; one breeding-thread participant found Niwot primocane berries not very tasty or even bad,^[10] while a zone-6/7 grower calls them delicious but not especially sweet and advises growing Niwot for the summer crop in zones 6 and colder.^[9] Ohio's Treasure is described by separate growers as bland and less productive than floricane types and as small and soft,^[9][10] and Explorer is reported to need a pollinator.^[10] A Colorado zone-5 grower reports that neither Ohio's Treasure nor Bristol produced a crop in three years there.^[9] These primocane-fruiting notes are attributed grower reports from GrowingFruit.org, not cultivar-release documentation, and outcomes vary by site.

Photos

References

• ↑ [1] Kew Plants of the World Online: Rubus occidentalis. Accepted name, first publication in 1753, native and introduced range, synonym set.

• ↑ [2] GBIF Species Match API: Rubus occidentalis. Accepted exact match in the GBIF backbone; family Rosaceae, genus Rubus.

• ↑ [3] NC State Extension Plant Toolbox: Rubus occidentalis (Black Raspberry). Species description, habit, flowers, fruit, flavor, ethnobotany, zones and cultural notes.

• ↑ [4] Raspberries for the Home Fruit Planting (OSU Extension fact sheet HYG-1421). Bramble crop guidance: establishment, spacing, trellising, virus isolation, cultivar table, nutrition note.

• ↑ [5] USDA PLANTS Database: Rubus occidentalis characteristics. Documentary characteristics: minimum temperature, pH, moisture, drought and salinity response, growth form, stratification and propagation methods.

• ↑ [6] TropicalFruitForum: growing raspberries and Rubus in central Florida. First-hand marginal-climate report on shading, water, limestone soil and black raspberry flavor.

• ↑ [7] Wright, Welch, Miller & Funt: Black Raspberry (Rubus occidentalis) Cultivar Study, Ohio State University South Centers. Original field trial: cultivar geneaology, frost blossom kill, berry weight, yield and Brix.

• ↑ [8] GrowingFruit.org: Bristol vs Jewel black raspberry growth. First-hand grower comparisons of vigor, primocane production, ripening dates and tip-rooting practice.

• ↑ [9] GrowingFruit.org: Niwot vs Ohio's Treasure vs other black raspberries. First-hand grower reports on primocane-fruiting cultivars, fall-crop limits and fruit size and flavor.

• ↑ [10] GrowingFruit.org: Experiments in black raspberry breeding. First-hand grower reports on cultivar longevity, container growing, Niwot, Ohio's Treasure and Explorer.

Image credits

• Black_Raspberries,_Underhill.jpg — ripe black raspberries (Rubus occidentalis), Underhill, Vermont, July 2005: Cstaffa (via English Wikipedia), file page, public domain.

• Black_Raspberry_(Rubus_occidentalis)_-_Guelph,_Ontario_2013-07-20.jpg — black raspberry plant in fruit (Rubus occidentalis), Guelph, Ontario: Ryan Hodnett, file page, CC BY-SA 4.0.

• Red_ripening_black_raspberries_(19360409510).jpg — red-ripening black raspberries (Rubus occidentalis) before the final dark stage: David Whelan (Flickr, upload by Fae), file page, CC0 public domain dedication.

• Rubus_occidentalis_15-p.bot-rubus.occi-01.jpg — black raspberry stem, branches and fruits (polydrupes) (Rubus occidentalis): Gilles Ayotte (as Cephas), file page, CC BY-SA 4.0.

• Rubus_occidentalis_(35029818313).jpg — black raspberry (Rubus occidentalis): Karen Hine, file page, CC BY-SA 2.0.