Red raspberries are synonymous with summertime dinner parties, being delicious fresh fruits to eat alongside sweet cream, cakes and ice cream. Not true botanical berries, raspberry fruits are a hollow cap of succulent beads. Each bead is an ovary with a seed inside, and known as a drupe. Overall, the conglomeration of all the tiny drupes makes the raspberry an aggregate fruit.
Generally speaking, red raspberries are a plant species known as Rubus idaeus. There are in total about 250 species of "raspberry" plants in the world; some can be called brambles and thimbleberries and include the closely related black raspberries (Rubus occidentalis). Man has hybridized red raspberries with any number of other members of the brambles to yield hardier plants, different fruit sizes and flavors, as well as names. In fact, the cross between a raspberry and a blackberry yielded what we call a loganberry.
Red raspberries are native to most of the temperate areas of the Northern Hemisphere. Plants native to northern Europe and northwestern Asia are taxonomically specified as Rubus idaeus subspecies idaeus, while those native to North America as Rubus idaeus subspecies strigosus. The North America subspecies grows from Alaska to Newfoundland and then southward to Arizona and northern Mexico and Tennessee, according to the U.S. Forest Service.
Man's favor of red raspberry plants led him to carry plants with him as new lands were discovered and populated. Therefore, the Eurasian raspberry found its way into North America, where it was planted in pioneer gardens as well as escaped to grow alongside and share its genetics with the native American red raspberries.
Black raspberries are native to the western United States. Although edible, these fruits today are mainly grown to produce a purple food dye. In fact, according to "Economic Botany: Plants in Our World," this non-toxic dye is used on surfaces of meat cuts or other fresh foods and their packaging. Black raspberries must not be confused with blackberries (Rubus fruticosus), which have a soft solid core to their raspberry-like fruits. Remember, black raspberries peel from the plant to reveal a hollow, cap-like fruit mass.
Since raspberry plants remain susceptible to a fair number of diseases, development of new varieties (cultivars) of raspberry plants continues, the result of cross-breeding or selection of other genetic mutations. Plants demonstrating beneficial characteristics like improved disease resistance, ever-blooming/bearing, larger-sized fruits, more flavorful fruits or better cold hardiness are released to nurseries for gardeners to grow in home landscapes. Complex breeding muddies the genetic lineage of modern raspberries as well as their identity, since there are now red raspberries that physically are colored red-purple (violet), translucent pale yellow or black.