BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Lewisia rediviva | Bitterroot 



GENERAL BOTANICAL CHARACTERISTICS : 
Bitterroot is a native, cool-season, low-growing, ephemeral, perennial
forb.  Most of the biomass consists of a thick, often branching taproot
up to 12.8 inches (32 cm) long.  Bitterroot has a short caudex with
densely clustered succulent leaves at the caudex crown.  The fruit is a
capsule with small, round seeds [4,12,16,17,18].


RAUNKIAER LIFE FORM : 
   Geophyte


REGENERATION PROCESSES : 
Differentiation of floral buds appears to be triggered by short-day
photoperiods and/or cool fall temperatures [17].  Blooming occurs in
spring.  Flowers remain open for 2 to 3 days and are pollinated by
insects, usually native bees.  Seed is dispersed by wind and gravity
[4,5,14,26].  Bitterroot seed in Craters of the Moon National Monument,
Idaho, was positively correlated with cushion eriogonum (Eriogonum
ovalifolium), which probably acts as a seedtrap.  Density of soil-stored
bitterroot seed on bare ground was 0.7 seeds per square foot (83/sq m),
while seed density beneath cushion eriogonum was 52.7 per square foot
(567/sq m) [5].  Germination rates are highest after cold stratification
[4].  Seedling establishment may be facilitated by mat-forming plants
such as cushion eriogonum; Day and Wright [5] have hypothesized that
cushion eriogonum is a nurse plant for bitterroot in south-central
Idaho.



SITE CHARACTERISTICS : 
Bitterroot is found in dry western climates where the majority of
precipitation occurs in cooler seasons, and soil dessication in summer
is common [17].  It grows on well-drained, exposed gravelly benches,
river bars, plains, stony slopes, and open ridges [7,12,22].  It is
found at the following elevations in several western states:

          feet              meters

CA:  2,500 to  6,000      762-1,829 [18]
CO:  7,000 to  9,000    2,134-2,743 [12]
MT:  3,000 to  6,000      914-1,829 [16]
UT:  4,790 to 10,335    1,460-3,150 [24]

Lewisia rediviva variety minor occurs from 6,500 to 9,000 feet
(1,981-2,742 m) in elevation [18].            

Plant associates not listed in Distribution and Occurrence are as
follows: 

In palouse prairies of eastern Washington and Oregon and western Idaho
and Montana, bitterroot is associated with Idaho fescue (Festuca
idahoensis), bluebunch wheatgrass (Pseudoroegneria spicata), Sandberg
bluegrass (Poa secunda), western wheatgrass (Pascopyrum smithii),
junegrass (Koeleria cristata), cheatgrass (Bromus tectorum), biscuitroot
(Lomatium spp.), wooly groundsel (Senecio canus), cushion eriogonum, and
mountain pink (Douglasia montana) [3,10].

In mountain shrublands of Utah and Colorado, bitterroot is associated
with Gambel oak (Quercus gambelii), bigtooth maple (Acer
grandidentatum), serviceberry (Amelanchier spp.), bitterbrush (Purshia
tridentata), and silver sagebrush (Artemesia cana) [24].


SUCCESSIONAL STATUS : 
Obligate Initial Community Species

Bitterroot is a colonizer in primary succession.  The thick taproot is
well-adapted to initial colonization of rock crevices.  Bitterroot in
Craters of the Moon National Monument, Idaho, is a primary colonizer of
cinder cones [5].  Bitterroot requires full sunlight [16,22], and
generally occurs in initial communities and/or early seres in secondary
succession [10,11].  Researchers in Alberta found that plants
established where prevailing winds broke up sod on hillsides [26].


SEASONAL DEVELOPMENT : 
Bitterroot phenology is as follows in the Bitterroot Valley of western
Montana [17]:

new leaves appear:  late October
flower buds initiated:  early November
leaf elongation:  April
leaves wither:  early May
flowering:  early June
flower abscission and seed dispersal:  late June

Summer dormancy is broken by the onset of precipitation.  The period of
fall growth therefore varies; bitterroot in western Montana has
initiated leaf and flower bud growth as early as August or as late as
November, depending on seasonal rainfall [17].

Development is eastern Washington is as follows [4]:

seeds germinate:  November
new leaves appear:  September to October
flowering:  May to June
flower abscission and seed dispersal:  June to July

Related categories for Species: Lewisia rediviva | Bitterroot