Rubus parviflorus is native to western North America from Alaska south as far as California, New Mexico, Chihuahua, and San Luis Potosí. Its range extends east to the Rocky Mountains and discontinuously to the Great Lakes Region. It grows from sea level in the north, up to elevations of 3,000 m (10,000 ft) in the south.
Rubus parviflorus is a dense shrub up to 2.5 meters (8.2 ft) tall with canes no more than 1.5 centimeters (0.59 in) in diameter, often growing in large clumps which spread through the plant's underground rhizome. Unlike many other members of the genus, it has no prickles. The leaves are palmate, up to 20 centimeters (7.9 in) across (much larger than most other Rubus species), with five lobes; they are soft and fuzzy in texture.
The flowers are 2 to 6 centimeters (0.79 to 2.36 in) in diameter, with five white petals and numerous pale yellow stamens. The flower of this species is among the largest of any Rubus species, making its Latin species name parviflorus ("small-flowered") a misnomer.
The plant produces edible composite fruit approximately a centimeter (0.4 inches) in diameter, which ripen to a bright red in mid to late summer. Like other raspberries it is not a true berry, but instead an aggregate fruit of numerous drupelets around a central core. The drupelets may be carefully removed separately from the core when picked, leaving a hollow fruit which bears a resemblance to a thimble, perhaps giving the plant its name.
Thimbleberry fruits are smaller, flatter, and softer than raspberries, and have many small seeds. Because the fruit is so soft, it does not pack or ship well, so thimbleberries are rarely cultivated commercially.
However, wild thimbleberries can be made into a jam which is sold as a local delicacy in some parts of their range, notably in the Keweenaw Peninsula of Upper Michigan. Thimbleberry jam is made by combining equal volumes of berries and sugar and boiling the mixture for two minutes before packing it into jars. The fruits can be eaten raw or dried.
Rubus parviflorus is cultivated by specialty plant nurseries as an ornamental plant, used in traditional, native plant, and wildlife gardens, in natural landscaping design, and in habitat restoration projects. The fruit has fragrance. Thimbleberry plants can be propagated most successfully by planting dormant rhizome segments, as well as from seeds or stem cuttings.
The flowers support pollinators, including of special value to Native bees, honeybees, and bumblebees. The fruit is attractive to birds. It is the larval host and a nectar source for the yellow-banded sphinx butterfly.
A double-flowered form of the thimbleberry was discovered near Squamish, BC, by Iva Angerman (1903–2008) of West Vancouver, BC. This clone does not appear to be in commerce, but is grown in the Botanic Garden of the University of British Columbia, Vancouver, and in the Native Plant Garden of the Royal British Columbia Museum, Victoria.
Another double-flowered thimbleberry was found about 1975 by Bob Hornback on Starrett Hill, Monte Rio, California and given the cultivar name 'Dr. Stasek', after an art instructor at Sonoma State University.
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