Name: Trailing blackberry (Rubus ursinus), also known as California blackberry, Pacific blackberry, Pacific dewberry, and a number of other common names.
Range and typical habitat(s): West coast of North America from southern British Columbia to northern Baja California, east to the Cascade mountains, and scattered through the Rocky Mountains in Idaho, Washington, and Montana.
Distinguishing physical characteristics (size, colors, overall shapes, detail shapes): Summer is here, and that means blackberries are ripening on the vine! Here in the Pacific Northwest where I live we have multiple species, all featuring delectable, juicy berries, but only one is native. The trailing blackberry distinguishes itself through a slender, biennial vine, pale green to bluish-purple in color, with tiny thorns all along its length. (Be careful when handling this vine, as the thorns easily detach and become embedded in your skin!) Some vines may exceed six feet in length, and each plant may produce several of these from a central perennial root system.
The leaves of trailing blackberry generally have three leaflets, though one or five may occasionally be seen, and they are dark green above with a pale green to white underside. Each leaflet is oval in shape with a pointed tip and a deeply serrated edge that has larger serrations interspersed with groups of smaller, finer serrations, and generally will not reach more than about four inches in length. This species is deciduous, and loses its leaves over winter before growing new foliage in the spring.
First-year vines are not fertile; they will not produce flowers until their second year, after which they die. Like many other Rubus species, it has a flower with five white petals that rarely exceeds an inch in diameter, and the petals are particularly slender compared to others in the genus. The center is pale green to yellow with several dozen anthers on the flowers of male plants. Female plants, of course, are the only ones to bear small berries about 3/4″ or so long at the largest, which start out green, darken to red, and finally ripen at a deep purple to black. While smaller than commercially available blackberries, they are quite sweet and flavorful when ripe. Technically they are not true berries, but are instead composites of several tiny round drupelets each with its own seed, which is typical of Rubus fruit.
Trailing blackberry can grow quite quickly, and although it may clamber over other plants it generally does not out-compete them to the point of becoming a monoculture. It is also a quite hardy plant and can colonize disturbed ground with ease as long as there is plenty of sunlight. The vines can become a bit of a tripping hazard in places with high foot traffic, but are easily trimmed back without killing the entire plant. In addition to seeds, trailing blackberry can also grow colonies of clones wherever its vine touches the ground.
Other organisms it could be confused with and how to tell the difference:
In its native range, trailing blackberry is a rather unique little plant. It may occasionally be confused with the invasive Himalayan blackberry (Rubus armeniacus). However, the latter grows on large, thick canes up to thirty feet long that can grow tall and arch over, and which create massive thickets that choke out any other plant life. The leaves of Himalayan blackberry are also larger and rounder–up to eight inches long–and more typically have five palmately compound leaflets instead of three, though three leaflets may sometimes be seen. The flowers have rounder petals, and the berries are much larger, sometimes exceeding an inch in length.
Cutleaf or evergreen blackberry (Rubus laciniatus) is another invasive species found within trailing blackberry’s range. Like Himalayan, the cutleaf species also grows thick, long canes. It is mainly distinguished by its leaves, which have three leaflets that are deeply serrated/toothed and have a jagged appearance–hence the name “cutleaf.”
Black or whitebark raspberry (Rubus leucodermis) has berries which superficially look like those of trailing blackberry. However, once again the canes of this species are thicker and woodier than the trailing vines, and they have a distinctive white to pale purple glaucous coloration. The leaflets are larger than those of trailing blackberry, with first-year leaves having five pinnate leaflets, and second-year having three. The berries are larger and rounder, generally not exceeding 1/2″ in diameter. The overall appearance of the plant is of a taller, more upright shrub than a series of vines trailing over ground and other surfaces.
Anything else worth mentioning? Like other Rubus species, the berries of trailing blackberry are edible, and the leaves may be made into tea. If cultivating this species in your native plant garden, be aware it grows quite quickly, though it can be trained up a trellis with some effort.