Rubus

Bramble bushes typically grow as shrubs (though a few are herbaceous), with their stems being typically covered in sharp prickles. They grow long, arching shoots that readily root upon contact with soil, and form a soil rootstock from which new shoots grow in the spring. The leaves are either evergreen or deciduous, and simple, lobed, or compound. The shoots typically do not flower or set fruit until the second year of growth (i.e. they are biennial). The rootstock is perennial. Most species are hermaphrodites, with male and female parts being present on the same flower. Bramble fruits are aggregate fruits formed from smaller units called drupelets.

Around 60-70% of species of Rubus are polyploid (having more than two copies of each chromosome), with species ranging in ploidy from diploid (2×, with 14 chromosomes) to tetradecaploid (14×).

Modern classification

Rubus is the only genus in the tribe Rubeae.

Rubus is very complex, particularly within the blackberry/dewberry subgenus (Rubus), with polyploidy, hybridization, and facultative apomixis apparently all frequently occurring, making species classification of the great variation in the subgenus one of the grand challenges of systematic botany. In publications between 1910 and 1914, German botanist Wilhelm Olbers Focke attempted to organize the genus into 12 subgenera, a classification system that since became widely accepted, though modern genetic studies have found that many of these subgenera are not monophyletic.

Some treatments have recognized dozens of species each for what other, comparably qualified botanists have considered single, more variable species. On the other hand, species in the other Rubus subgenera (such as the raspberries) are generally distinct or else involved in more routine one-or-a-few taxonomic debates, such as whether the European and American red raspberries are better treated as one species or two (in this case, the two-species view is followed here, with R. idaeus and R. strigosus both recognized; if these species are combined, then the older name R. idaeus has priority for the broader species).

The classification presented below recognizes 13 subgenera within Rubus, with the largest subgenus (Rubus) in turn divided into 12 sections. Representative examples are presented, but many more species are not mentioned here. A comprehensive 2019 study found subgenera Orobatus and Anoplobatus to be monophyletic, while all other subgenera to be paraphyletic or polyphyletic. Molecular data have backed up classifications based on geography and chromosome number, but following morphological data, such as the structure of the leaves and stems, do not appear to produce a phylogenetic classification.

Fossil record

The genus has a likely North American origin, with fossils known from the Eocene-aged Florissant Formation of Colorado, around 34 million years old. Rubus expanded into Eurasia, South America, and Oceania during the Miocene. Fossil seeds from the early Miocene of Rubus have been found in the Czech part of the Zittau Basin. Many fossil fruits of †Rubus laticostatus, †Rubus microspermus and †Rubus semirotundatus have been extracted from bore hole samples of the Middle Miocene freshwater deposits in Nowy Sacz Basin, West Carpathians, Poland.

Species

Rubus is a diverse genus, with estimates of the number of species varying from 250 to over 1,000, found across all continents except Antarctica. Better-known species include:

• Rubus aboriginum, garden dewberry
• Rubus allegheniensis, Allegheny blackberry
• Rubus arcticus, Arctic raspberry
• Rubus argutus, sawtooth raspberry
• Rubus armeniacus, Himalayan blackberry
• Rubus caesius, European dewberry
• Rubus canadensis, smooth blackberry
• Rubus chamaemorus, cloudberry
• Rubus cockburnianus, white-stemmed bramble
• Rubus coreanus, bokbunja
• Rubus crataegifolius - santtalgi
• Rubus deliciosus
• Rubus domingensis
• Rubus ellipticus
• Rubus flagellaris, northern dewberry
• Rubus fraxinifolius, mountain raspberry
• Rubus glaucus
• Rubus hawaiensis
• Rubus hispidus, swamp dewberry
• Rubus idaeus, red raspberry
• Rubus illecebrosus
• Rubus laciniatus, cut-leaved blackberry
• Rubus leucodermis, whitebark raspberry
• Rubus moluccanus
• Rubus nepalensis
• Rubus nivalis, snow raspberry
• Rubus niveus
• Rubus occidentalis, black raspberry
• Rubus odoratus, purple-flowered raspberry
• Rubus parviflorus, thimbleberry
• Rubus pedatus
• Rubus pensilvanicus, Pennsylvania blackberry
• Rubus phoenicolasius, wineberry
• Rubus probus
• Rubus pubescens, dwarf raspberry
• Rubus rosifolius, roseleaf bramble
• Rubus saxatilis, stone bramble
• Rubus spectabilis, salmonberry
• Rubus tricolor
• Rubus trivialis, Southern dewberry
• Rubus ulmifolius, elm-leaved blackberry
• Rubus ursinus, trailing blackberry
• Rubus vestitus, European blackberry

A more complete subdivision is as follows:

Hybrid berries

The term "hybrid berry" is often used collectively for those fruits in the genus Rubus, which have been developed mainly in the U.S. and U.K. in the last 130 years. As Rubus species readily interbreed and are apomicts (able to set seed without fertilisation), the parentage of these plants is often highly complex, but is generally agreed to include cultivars of blackberries (R. ursinus, R. fruticosus) and raspberries (R. idaeus). The British National Collection of Rubus stands at over 200 species, and although not within the scope of the National Collection, also hold many cultivars.

The hybrid berries include:-

• loganberry (California, U.S., 1883) R. ×loganobaccus, a spontaneous hybrid between R. ursinus 'Aughinbaugh' and R. idaeus 'Red Antwerp'
• boysenberry (U.S., 1920s) - a hybrid between R. idaeus and R. × loganobaccus
• nectarberry - a suspected variant of boysenberry, a hybrid between R. idaeus and R. × loganobaccus
• olallieberry (U.S., 1930s) - a hybrid between the loganberry and youngberry, themselves both hybrid berries
• veitchberry (Europe, 1930s) - a hybrid between R. fruticosus and R. idaeus
• skellyberry (Texas, U.S., 2000s) - a hybrid between R. invisus and R. phoenicolasius
• marionberry (1956) - now thought to be a blackberry cultivar R. 'Marion'
• silvanberry - R. 'Silvan', a hybrid between R. 'Marion' and boysenberry
• tayberry (Dundee, Scotland, 1979) - another blackberry/raspberry hybrid
• tummelberry, R. 'Tummel' - from the same Scottish breeding programme as the tayberry
• hildaberry (1980s) - a tayberry/boysenberry hybrid discovered by an amateur grower
• youngberry - a complex hybrid of raspberries, blackberries, and dewberries

Etymology

The generic name means blackberry in Latin and was derived from the word ruber, meaning "red".

The blackberries, as well as various other Rubus species with mounding or rambling growth habits, are often called brambles. However, this name is not used for those like the raspberry that grow as upright canes, or for trailing or prostrate species, such as most dewberries, or various low-growing boreal, arctic, or alpine species. The scientific study of brambles is known as "batology". "Bramble" comes from Old English bræmbel, a variant of bræmel.