Twinflower

More info for the terms: fire use, prescribed fire, restoration

The following Research Project Summaries provide information on prescribed
fire use and postfire response of plant community species including twinflower:

• Vegetation response to restoration treatments in ponderosa pine-Douglas-fir
  forests of western Montana


• Understory recovery after burning and reburning quaking aspen stands in
  central Alberta

twinflower
northern twinflower
western twinflower

More info for the terms: capsule, duff, forest, fruit, litter, root crown, shrub, stolon

Twinflower is a native, evergreen, dwarf shrub [20].  It is creeping or
trailing in growth form, with numerous short aerial stems rising from
the stolon.  With time, stolons may become shallowly buried beneath
litter and duff layers [17]; maximum depth of twinflower stolons in a
mixed conifer old-growth forest of central Oregon was 0.11 inch (0.27
cm) below the soil surface [2].  Aerial stems become woody with age but
rarely exceed 0.12 inch (0.30 cm) in diameter.  The root crown of these
stems is positioned at or just beneath the duff or soil surface [17].
Twinflower has a shallow, fibrous network of roots with their growing
points within and slightly below the duff layer [56].  In the central
Oregon study mentioned above, average root depth was 0.11 inch (0.28 cm)
[2].  Twinflower fruit is a small, dry, one-seeded capsule [30,62].

The typical subspecies of twinflower is distributed from eastern Alaska
across Siberia and northern Europe [35].  Pacific twinflower occurs
along the West Coast from southern Alaska to northern California
[35,55].  American twinflower is distributed from interior Alaska across
Canada to Newfoundland and south to northern Arizona and New Mexico,
South Dakota, Indiana, West Virginia, and New Jersey [28,35,41].

More info for the terms: duff, fire regime, seed

Twinflower is a fire avoider [56]. During fire, small patches of
twinflower in draws, moist duff, or other protected places usually
escape burning [15,17].  Twinflower most commonly establishes in burn
areas from stolons produced by these unburned plants.  It also
establishes from animal-dispersed seed [3,56].

FIRE REGIMES :
Find fire regime information for the plant communities in which this
species may occur by entering the species name in the FEIS home page under
"Find FIRE REGIMES".

More info for the terms: forbs, forest, fuel

Brown and Marsden [11] have developed an equation for estimating fuel
weight of twinflower and other small woody plants, grasses, and forbs in
coniferous forests of western Montana and northern Idaho.  Brown [10]
developed a method of determining bulk densities of nonuniform surface
fuels in subalpine fir/twinflower and other forest types of that region.

More info on this topic.

More info for the term: chamaephyte

Chamaephyte

More info for the terms: peatland, xeric

Twinflower grows in soils derived from a variety of parent materials.
Soil texture and nutrient levels also vary, and soil moisture levels
range from xeric to hydric [13,16,30,59].  The pH range of
twinflower-supporting soils in peatland bogs of Minnesota and
Saskatchewan is 4.0 to 7.0 [31,39].  Twinflower occurs on all aspects
[18].  It is found at the following elevations:

                                  feet            meters
northern ID; western MT      2,200 - 5,900      670 - 1,800 [13,25]
southern CO; northern NM     7,900 - 9,800    2,400 - 2,900 [19]
UT                           6,000 - 9,600    1,830 - 2,900 [67]
CA                           4,000 - 8,000    1,200 - 2,400 [55]

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This species is known to occur in association with the following cover types (as classified by the Society of American Foresters):

     1  Jack pine
     5  Balsam fir
    12  Black spruce
    13  Black spruce - tamarack
    15  Red pine
    16  Aspen
    18  Paper birch
    20  White pine - northern red oak - red maple
    21  Eastern white pine
    22  White pine - hemlock
    23  Eastern hemlock
    24  Hemlock - yellow birch
    25  Sugar maple - beech - yellow birch
    26  Sugar maple - basswood
    27  Sugar maple
    30  Red spruce - yellow birch
    31  Red spruce - sugar maple - beech
    32  Red spruce
    33  Red spruce - balsam fir
    35  Paper birch - red spruce - balsam fir
    37  Northern white-cedar
    38  Tamarack
    51  White pine - chestnut oak
    60  Beech - sugar maple
   107  White spruce
   201  White spruce
   202  White spruce - paper birch
   203  Balsam poplar
   204  Black spruce
   205  Mountain hemlock
   206  Engelmann spruce - subalpine fir
   210  Interior Douglas-fir
   211  White fir
   212  Western larch
   213  Grand fir
   215  Western white pine
   216  Blue spruce
   218  Lodgepole pine
   251  White spruce - aspen
   252  Paper birch
   253  Black spruce - white spruce
   254  Black spruce -  paper birch

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This species is known to occur in the following ecosystem types (as named by the U.S. Forest Service in their Forest and Range Ecosystem [FRES] Type classification):

   FRES10  White - red - jack pine
   FRES11  Spruce - fir
   FRES18  Maple - beech - birch
   FRES19  Aspen - birch
   FRES20  Douglas-fir
   FRES21  Ponderosa pine
   FRES22  Western white pine
   FRES23  Fir - spruce
   FRES24  Hemlock - Sitka spruce
   FRES25  Larch
   FRES26  Lodgepole pine
   FRES27  Redwood
   FRES28  Western hardwoods
   FRES38  Plains grasslands
   FRES44  Alpine

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This species is known to occur in association with the following plant community types (as classified by Küchler 1964):

More info for the terms: bog, forest

   K001  Spruce - cedar - hemlock forest
   K002  Cedar - hemlock - Douglas-fir forest
   K003  Silver fir - Douglas-fir forest
   K004  Fir - hemlock forest
   K005  Mixed conifer forest
   K006  Redwood forest
   K008  Lodgepole pine - subalpine forest
   K011  Western ponderosa forest
   K012  Douglas-fir forest
   K013  Cedar - hemlock - pine forest
   K014  Grand fir - Douglas-fir forest
   K015  Western spruce - fir forest
   K016  Eastern ponderosa forest
   K017  Black Hills pine forest
   K018  Pine - Douglas-fir forest
   K020  Spruce - fir - Douglas-fir forest
   K021  Southwestern spruce - fir forest
   K028  Mosaic of K002 and K026
   K029  California mixed evergreen forest
   K052  Alpine meadows and barren
   K066  Wheatgrass - needlegrass
   K067  Wheatgrass - bluestem - needlegrass
   K093  Great Lakes spruce - fir forest
   K094  Conifer bog
   K095  Great Lakes pine forest
   K096  Northeastern spruce - fir forest
   K106  Northern hardwoods
   K107  Northern hardwoods - fir forest
   K108  Northern hardwoods - spruce forest
   K109  Transition between K104 and K106

Twinflower is killed even by low-intensity fire [9,17,23,50,65].

Bighorn sheep of Alaska and caribou of northern Canada use twinflower as
incidental forage [7,61].  It provides 9.7 percent of winter diets of
Roosevelt elk of British Columbia, Washington, and Oregon, but only 0.5
percent of their summer diets [40].  It is listed as a food item of
ruffed grouse of Idaho [36].

More info for the terms: forest, grassland, habitat type, hardwood, taiga

Twinflower occurs in several grassland and many hardwood and coniferous
forest types.  It is named as a dominant understory or indicator species
in numerous published classifications.  A partial listing is as follows:

Preliminary plant associations of the southern Oregon Cascade Mountain
   Province [4]
Preliminary plant associations of the Siskiyou Mountain Province [5]
Ecology of wetlands in Big Meadows, Rocky Mountain National Park,
   Colorado [12]
Forest habitat types of northern Idaho:  a second approximation [13]
Classification of montane forest community types in the Cedar River
   drainage of western Washington, U.S.A. [18]
A classification of forest habitat types of northern New Mexico and
   southern Colorado [19]
Classification, description, and dynamics of plant communities after
   fire in the taiga of interior Alaska [24]
Forest vegetation of the Black Hills National Forest of South Dakota and
   Wyoming:  a habitat type classification [34]
Plant communities of Voyageurs National Park, Minnesota, U.S.A. [46]
Forest habitat types of Montana [57]

More info for the terms: forb, shrub, vine

Forb-Shrub-Vine

Dry matter nutrient content of twinflower in Manitoba is 7.0 percent
protein and 39.3 percent acid detergent fiber.  Estimated dry matter
digestibility for caribou is 59.5 percent [60].

     AK  AZ  CA  CO  CT  ID  IL  IN  ME  MD
     MA  MI  MN  MT  NH  NJ  NM  NY  ND  OH
     OR  PA  RI  SD  UT  VT  WA  WV  WI  WY
     AB  BC  MB  NB  NF  NT  NS  ON  PE  PQ
     SK  YT

More info on this topic.

Twinflower blooms from June through September throughout most of its
range [30,36].  Flowers last about 7 days, and fruits mature
approximately 36 days after flowering [32].  The leaves persist for 2
years [21]; season of leaf abscission was not reported in the
literature.

More info for the terms: cover, density, duff, frequency, relative density

Twinflower sometimes colonizes new areas after fire.  In northwestern
Montana, broadcast burning was conducted to remove slash following
logging of subalpine fir (Abies lasiocarpa).  Twinflower had previously
been absent from the site.  Twinflower seedlings first appeared at
postfire year 6, showing 1 percent ground cover.  At postfire year 9,
twinflower cover was still at 1 percent [65].  Broadcast burning was
also conducted at a nearby site where prefire twinflower cover was 8
percent.  The fire removed 11 percent of the duff, and all existing
twinflower was killed.  As with the previously mentioned fire,
twinflower seedlings first established at postfire year 6, showing 1
percent cover.  By postfire year 8, twinflower cover at this site had
increased to 8 percent [65].

In Pacific silver fir (Abies amabilis)-subalpine fir forests of central
British Columbia, twinflower frequency on 4- to 22-year-old burns was 60
percent.  Frequency on 37- to 75-year-old burns was 70 percent [26].

Two consecutive annual, low-intensity prescribed fires were conducted on
the Petawawa Experimental Station in Ontario.  Prefire relative
twinflower density was 9.65 percent.  After the first fire, twinflower
relative density lowered to 0.14 percent.  It dropped to 0.11 percent
after the second fire [52].

More info for the terms: root crown, secondary colonizer

   Surface rhizome/chamaephytic root crown
   Secondary colonizer - off-site seed

More info for the terms: density, forest, litter, seed

Vegetative reproduction by stolons is the primary method of twinflower
regeneration [2,21].  Twinflower first produces stolons at 5 to 10 years
of age [21].

Sexual reproduction is uncommon, but seedlings are occasionally found in
burned or other disturbed areas [21,65].  Pollination is effected by
native bees and syrphid wasps [6,30]; rarely, plants are self-fertile
[30].  Twinflower produces abundant seed [29], which apparently does not
persist in seed banks.  A study in a paper birch-balsam fir (Betula
papyrifera-Abies balsamea) forest on Mont Jacques-Cartier in Quebec
showed a twinflower seed density of six seeds per square meter, with
none of the seeds proving viable [54].  In British Columbia, Kellman
[42] found only one viable twinflower seed in 34 samples collected from
the litter, A, and B soil horizons.  Twinflower seed attaches to the
fur, hides, or feathers of animals, which serve as dispersal agents.

More info on this topic.

This species can be found in the following regions of the western United States (according to the Bureau of Land Management classification of Physiographic Regions of the western United States):

    1  Northern Pacific Border
    2  Cascade Mountains
    3  Southern Pacific Border
    4  Sierra Mountains
    5  Columbia Plateau
    6  Upper Basin and Range
    8  Northern Rocky Mountains
    9  Middle Rocky Mountains
   10  Wyoming Basin
   11  Southern Rocky Mountains
   12  Colorado Plateau
   15  Black Hills Uplift
   16  Upper Missouri Basin and Broken Lands

More info on this topic.

More info for the terms: climax, forest, peat, presence

Twinflower tolerates a wide spectrum of light intensity.  It grows in
full daylight in alpine meadows and peat bogs [12,39], but subcanopy
light has been measured at 2 percent of full daylight in a closed-canopy
mountain hemlock-western redcedar (Tsuga heterophylla-Thuja
plicata)/twinflower type near Vancouver, British Columbia [51].

Twinflower is found in recently disturbed, seral, and climax plant
communities.  Irwin [37] reported it as "abundant" after shelterwood
cutting in a western hemlock-western redcedar forest of northern Idaho.
Several authors have noted its presence in various climax forest types
[13,17,18,24,25,38].

In a study of understories of young (30-80 yrs), mature (80-195 yrs),
and old-growth (195-900 yrs) Douglas-fir forests of the Cascade Range of
Washington and Oregon, percent occurrence of twinflower by forest age
was as follows [63]:

     young:       89
     mature:      80
     old-growth:  98

The currently accepted scientific name of twinflower is Linnaea borealis
L. [28,33,55,62,62]. It is a monotypic genus [28]. Recognized
subspecies are as follows:

Linnaea borealis ssp. borealis [35]
Linnaea borealis sps. americana (Forbes) Hult. [35,45] (American twinflower)
Linnaea borealis ssp. longiflora (Torr.) Hult. [35,55,62] (Pacific twinflower)

Some authorities [33,62] recognize L. b. ssp. borealis and L. b. ssp.
longiflora as the only distinct subspecies of twinflower.