Rubus parviflorus

Thimbleberry

Thimbleberry
Photo © 1999 by Earl J.S. Rook

Flora, fauna, earth, and sky...
The natural history of the northwoods


Name:

  • Rubus, from the Latin, "bramble, briar"
  • parviflorus, from the Latin parvus, "small, little, insignificant," and florus, "bloom or flower"; hence, "small flowered".
  • Thimbleberry, from the shape of the fruit.
  • Other common names include Western Thimbleberry, Salmonberry, Mountain Sorrel, White Flowering Raspberry, Western Thimble Raspberry

Taxonomy:

  • Kingdom Plantae, the Plants
    • Division Magnoliophyta, the Angiosperms (flowering plants)
      • Class Magnoliopsida, the Dicotyledons
      • Subclass Rosidae, the Roses
        • Order Rosales, the Roses
          • Family Rosaceae, the Roses; with Amelanchier (Juneberries), Aronia (Chokeberries), Crataegus (Hawthorns), Malus (Apples), Physocarpus (Ninebark), Potentilla (Cinquefoils), Prunus (Cherries & Plums), Rosa (Roses), Sorbus (Mountain Ash), and Spiraea (Spirea)
            • Genus Rubus, the Brambles, with Dewberries, Raspberries, and Thimbleberry.
  • Taxonomic Serial Number: 25007
  • Hybrids between Thimbleberry and Red Raspberry (Rubus idaeus) have been reported. However, these hybrids are frequently sterile.

Description:

  • A low, scrambling or erect, unarmed deciduous shrub 1½'-8' tall.
  • Leaves large, simple, palmately-lobed; green above but pale beneath. Unequally serrate, turning brilliant orange to maroon in fall.
  • Stems perennial, few, erect, and simple. The stems, or canes, typically live for 2 to 3 years. Sterile first-year stems or primocanes, develop from buds at or below the ground surface and generally bear only leaves. During the second year, lateral branches, or floricanes, develop in the axils of the primocanes producing flowers and fruit. Growth is rapid under favorable growing conditions. Maximum rates of height growth often occur during the second and third years after establishment.
  • Twigs greenish and finely hairy.
  • Bark greyish, becoming flaky or shreddy with age.
  • Flowers showy white or, rarely, pink; in clusters of 2-7.
  • Fruit a "thimblelike" aggregate of numerous hairy, red or scarlet drupelets. These drupelets are nearly dry at maturity and fall apart readily when picked.

Identification:

Distribution:

  • Alaska to California and into northern Mexico; east to the Great Lakes States.

Habitat:

  • A variety of moist-to-dry and wooded-to-open sites. Commonly grows on open, wooded hillsides, along streambanks and canyons, on borders, and roadsides.
  • Frequently occurs as scattered individuals, but in some areas in dense contiguous patches.
  • Moderately shade tolerant.
  • Although persisting in closed stands, typically most abundant on disturbed sites within the forest canopy, such as cutover or windthrown areas.
  • Soil: Grows well on a variety of barren infertile soil types. Tolerates a wide range of soil temperature and pH but requires adequate soil moisture for good growth. Grows well on dry, rocky soil and deep well-drained loam. Growth best on loam or clay-loam, fair on sandy loams, but poor on gravel, sand, or clay. Grows well on soils derived from a variety of parent materials.
  • Persistent successional species which frequently dominates the understory during the first several decades after disturbance. It readily invades disturbed sites through rhizomes or seedling establishment. Generally occurs in greatest abundance in successional stands throughout its range but can persist in trace amounts in many climax forests. In many mature forest stands, thimbleberry may be restricted to disturbed sites such as clearings or areas of windthrow. Plant vigor and canopy cover generally decline as tree cover increases.
  • A nitrogen-demanding species and in some areas, begins to decline within 2-5 years after timber harvesting as soil nutrient levels decrease.

Fire:

  • Resistant to and generally enhanced by fire. In areas of rigorous fire suppression, fruit production and plant vigor have declined.
  • Well adapted to vigorously invade many types of burned sites through rhizomes or seed. Rhizome sprouting is an important postfire strategy which enables rapid reestablishment and spread.
  • A seed banker, also reestablishes through viable seed stored in the soil or duff. Seed banking is an important postfire regenerative strategy in Thimbleberry, a prolific seed producer. Thimbleberry seed is stimulated by fire and subsequently germinates in great numbers. Most seedling establishment occurs immediately after fire. Birds and mammals add to seedling establishment by transporting seed to the site. The capacity to regenerate through seed may be reduced by extremely hot, duff-reducing burns.
  • Although often top-killed, underground rhizomes generally survive. High severity fires which damage belowground regenerative structures may be most damaging to rhizomes. The aerial portions of relatively few plants actually survive fire, except for those on unusual microsites. Most seed stored on-site is probably unharmed by fire. Cover and vigor are generally enhanced by fire.
  • Capable of rapid, vigorous postfire spread through an extensive network of often deeply-buried rhizomes. Sprouting through surviving rootcrowns is also possible, although rhizome sprouting probably represents the primary mode of postfire regeneration. Multiple sprouts often replace the single stems observed in preburn communities.
  • Sprouting of rhizomes is favored by fires of low intensity and severity. Hot fires presumably offer greater potential for damaging underground regenerative structures.
  • Both sprouting and seedling establishment occur soon after fire. Growth is rapid and some plants occasionally bear fruit during the first postfire year. Thimbleberry generally reaches greatest abundance during the first years after fire and decreases as the overstory canopy closes. Dwindling soil nutrients may also contribute to its decline. Rhizome sprouting may produce dense cover up to 3' tall within 3 years after disturbance on some particularly moist sites. Dense early growth of aggressive species such as Fireweed (Chamerion angustifolium) can slow Thimbleberry establishment and growth.
  • Factors other than fire severity and intensity can also contribute to the rate of postfire recovery. Differences in the season of burn, plant density and vigor in the preburn community, site differences, and climatic factors all contribute to postfire recovery.

Associates:

  • Trees: Quaking Aspen (Populus tremuloides)
  • Shrubs: Twinflower (Linnaea borealis), Gooseberry (Ribes oxyacanthoides), willow (Salix spp.), Red Elderberry (Sambucus racemosa ssp. pubens),
  • Herbs: Wild Sarsaparilla (Aralia nudicaulis), Fireweed (Chamerion angustifolium), Fleabane (Erigeron eximus), Cow Parsnip (Heracleum lanatum), Lupine (Lupinus spp.), Bracken Fern (Pteridium aquilinum),
  • Ground Covers:
  • Mammals: Fruit is eaten by black bears and numerous smaller mammals, including coyote, chipmunk, raccoon, red fox, gray fox, red squirrel, and skunks. Provides cover for rabbits, red squirrel, black bear, and beaver.
  • Birds: Dense thickets form good nesting habitat for many small birds. Fruits are eaten by many birds, including the ruffed grouse, blue grouse, sharp-tailed grouse, American robin, thrushes, thrashers, towhees, gray catbird, northern cardinal, pine grosbeak, and brown thrasher.

History:

  • Traditionally used by indigenous peoples throughout its range. The fruit was eaten fresh in summer and dried for winter use. The bark was boiled and made into soap, and leaves were used to make a medicinal tea. Leaves were powdered and applied to burns to minimize scarring.

Uses:

  • Fruits edible, although palatability tends to be greater towards the eastern end of its range where rainfall is greater. Makes excellent jelly but too seedy for jam.
  • Young shoots may be eaten as greens; leaves have been used in making teas.

Reproduction:

  • Reproduces through seed but also regenerates vegetatively, even in the absence of disturbance. Capable of forming dense thickets through vegetative sprouting. Establishment from seed appears to be the primary mode of colonization in newly disturbed areas. Abundant seedling establishment typically occurs during the first year after disturbance.
  • Seed: Fruits, or "berries," are made up of an aggregate of numerous small red drupelets which fall to the ground when ripe. Seed averages ¾" in length.
  • Germination: Seeds have a hard, impermeable endocarp and dormant embryo. Consequently, germination is often slow. Allelopathic compounds produced by Bracken Fern (Pteridium aquilinum) can apparently inhibit germination and subsequent growth.
  • Seedbanking: Seed noted for its ability to remain viable for long periods of time. Seedbanking is believed to be an important postdisturbance regenerative strategy.
  • Seed dispersal by birds and mammals. Groups of seedlings occasionally germinate from rodent caches. However, small mammals generally play only a local role in seed dispersal. Birds often effect wider dispersal. Gravity may also aid in seed dispersal.
  • Vegetative regeneration: Strongly rhizomatous, also capable of vigorous sprouting from rootcrowns and roots. A single seedling can spread and occupy a relatively large area as rhizomes develop and spread. Most local expansion of this shrub is attributable to rhizome sprouting.

Propagation:

  • Initial propagation is reportedly more difficult than for other Rubus species.
  • Seed may be difficult to obtain commercially. Specific germination requirements have not yet been documented, but both warm and cold stratification are probably required. Most Rubus seeds require, as a minimum, warm stratification at 68 º to 86 º F for 90 days, followed by cold stratification at 36º to 41º F for an additional 90 days. These conditions are frequently encountered naturally as seeds mature in summer and remain in the soil through the cold winter months.
  • Laboratory tests indicate that exposure to sulfuric acid solutions or sodium hyperchlorite prior to cold stratification can enhance germination.
  • May be propagated vegetatively by planting stem cuttings or rhizome fragments. Best results have been obtained from starting dormant rhizome segments. Several cultivars are now commercially available.

Cultivation:

  • Hardy to USDA Zone 3 (average minimum annual temperature -40ºF)
  • Occasionally planted as an ornamental because of its attractive fragrant flowers and colorful fall foliage. Several cultivars have been developed, including `Golden' and `Colonel'.
  • It has the ability to form clumps which expand greatly once established.

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Last updated on 8 March, 2006