The impacts of fire and herbivory were the focus of a study done in Jasper National Park in Alberta, Canada,
where Lewis flax cover increased 2 years after fire in closed-canopy plots accessible to elk, but was not
significantly different on open-canopy plots or those where elk were excluded. Lewis flax cover in all
treatements averaged less than 1%. Plots were subjected to a low-intensity prescribed fire in May 1999,
with a rate of spread of 2 to 5 m/min and flame lengths of 10 to 20 cm with occasional "candling".
Percent ground cover of Lewis flax is detailed in the table below [2].
1998
2001
1998
2001
Fire adaptations: Lewis flax maintains some green basal foliage year round and, according to anecdotal information provided by Stevens and Monsen [117], "does not readily burn". Information provided by Wasser [131] indicates that Lewis flax may be killed by fire and that it may establish from seed after fire.
FIRE REGIMES: Lewis flax most commonly occurs in communities that are characterized by short fire-return intervals and mixed-severity or stand-replacement fire types.
The following table provides fire return intervals for plant communities and ecosystems where Lewis flax is important. 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".
Community or Ecosystem Dominant Species Fire Return Interval Range (years) bluestem prairie Andropogon gerardii var. gerardii-Schizachyrium scoparium 76,94] Nebraska sandhills prairie A. gerardii var. paucipilus-Schizachyrium scoparium 94] silver sagebrush steppe Artemisia cana 5-45 [58,101,139] sagebrush steppe A. tridentata/Pseudoroegneria spicata 20-70 [94] basin big sagebrush A. tridentata var. tridentata 12-43 [105] mountain big sagebrush A. tridentata var. vaseyana 15-40 [7,27,84] Wyoming big sagebrush A. tridentata var. wyomingensis 10-70 (x=40) [127,142] saltbush-greasewood Atriplex confertifolia-Sarcobatus vermiculatus 94] plains grasslands Bouteloua spp. 94,139] blue grama-needle-and-thread grass-western wheatgrass B. gracilis-Hesperostipa comata-Pascopyrum smithii 94,104,139] blue grama-buffalo grass B. gracilis-Buchloe dactyloides 94,139] grama-galleta steppe B. gracilis-Pleuraphis jamesii 94] cheatgrass Bromus tectorum 99,135] California montane chaparral Ceanothus and/or Arctostaphylos spp. 50-100 [94] curlleaf mountain-mahogany* Cercocarpus ledifolius 13-1,000 [9,107] mountain-mahogany-Gambel oak scrub C. ledifolius-Quercus gambelii <35 to <100 blackbrush Coleogyne ramosissima <35 to <100 western juniper Juniperus occidentalis 20-70 Rocky Mountain juniper J. scopulorum <35 [94] wheatgrass plains grasslands Pascopyrum smithii <5-47+ [94,101,139] Engelmann spruce-subalpine fir Picea engelmannii-Abies lasiocarpa 35 to >200 [6] pinyon-juniper Pinus-Juniperus spp. <35 [94] Rocky Mountain bristlecone pine P. aristata 9-55 [37,38] Rocky Mountain lodgepole pine* P. contorta var. latifolia 25-340 [12,13,124] Sierra lodgepole pine* P. contorta var. murrayana 35-200 [6] Colorado pinyon P. edulis 10-400+ [48,51,72,94] Jeffrey pine P. jeffreyi 5-30 western white pine* P. monticola 50-200 Pacific ponderosa pine* P. ponderosa var. ponderosa 1-47 [6] interior ponderosa pine* P. ponderosa var. scopulorum 2-30 [6,11,80] Arizona pine P. ponderosa var. arizonica 2-15 [11,31,109] aspen-birch Populus tremuloides-Betula papyrifera 35-200 [41,128] quaking aspen (west of the Great Plains) P. tremuloides 7-120 [6,53,83] mountain grasslands Pseudoroegneria spicata 3-40 (x=10) [5,6] Rocky Mountain Douglas-fir* Pseudotsuga menziesii var. glauca 25-100 [6,7,8] coastal Douglas-fir* P. menziesii var. menziesii 40-240 [6,88,103] oak-juniper woodland (Southwest) Quercus-Juniperus spp. <35 to <200 [94] Fayette prairie Schizachyrium scoparium-Buchloe dactyloides <10 [128] little bluestem-grama prairie S. scoparium-Bouteloua spp. <35 [94] *fire return interval varies widely; trends in variation are noted in the species reviewLewis flax maintains its green basal foliage year round and "does not readily burn". These traits may make it useful in vegetative fuel breaks to reduce the spread of fire [57,117]. It is frequently used in greenstripping projects throughout the Intermountain west because of its large ecological amplitude, ability to compete with annual weeds, ease of establishment, low flammability, and resilience and regrowth capabilities [85,95,96].
Postfire seeding with Lewis flax may be a viable postfire management option. Lewis flax appears to establish more readily on burned than unburned microsites following postfire broadcast seeding in meadows dominated by basin big sagebrush. A study done in the Toiyabe Mountains of Nevada measured the response of certain species while managing and restoring basin big sagebrush. The study sites were representative of dry meadow vegetation, and depth to water table was described as wet, intermediate, or dry. Treatment sites were burned and then seeded. Seedling establishment was recorded for each site from the 1st through the 3rd growing season. Lewis flax occurred on the wet and dry sites, but was not recorded on the control or intermediate sites [140,141].
Postfire establishment of Lewis flax seeded onto burned slash pile microsites under ponderosa pine in Arizona appears successful. Piles of slash were burned in February 2000 and subsequently underwent 1 of 5 site amelioration treatments. These treatments were: 1) no treatment; 2) living soil amendment (containing micro-organisms, arbuscular mycorrhizae, and plant propagules); 3) sterilized soil amendment (no propagules); 4) native seed amendment; and 5) seed/soil amendment. Establishment of Lewis flax was significantly higher (P ≤ 0.05) when seeded in conjunction with soil amendment. The average cover of Lewis flax for the native seed and seed/soil amendment plots is detailed below [75].
Treatment 4 Treatment 5 2000 0.01 ± 0.01 0.11 ± 0.04 2001 0 ± 0 0.13 ± 0.07Lewis flax occurs on valley bottoms, benches, slopes, ridges, and meadows, from prairie to alpine elevations [64,121]. It grows best in full sunlight and has little to no shade tolerance [61,62,121]. Site descriptions by state are provided below.
Climate: Lewis flax is suitable for sites with average annual precipitation that ranges from 10 to 23 inches (250-580 mm). Vigorous growth can be expected on sites averaging greater than 16 inches (410 mm) [61,121]. Lewis flax seedlings are "excellent competitors" in pinyon-juniper types that average <15 inches (380 mm) annual precipitation and are "medium competitors" on sites that average more than 15 inches (380 mm) annual precipitation. Mature plants are "medium competitors" at both of these precipitation levels [118].
Soils: Lewis flax thrives on well-drained porous soils ranging from moderately basic to weakly acidic. It is intolerant of poor drainage, flooding and high water tables [62,121].
Soil characteristics for sites that Lewis flax is known to occur on grassland types in North Dakota are as follows [136]:
The little bluestem-needle-and-thread grass-threadleaf sedge (Schizachyrium scoparium-Hesperostipa comata-Carex filifolia) type has soils that are composed of 70% sand, 18% silt, and 12% clay and pH between 7.3 to 8.6. These soils are relatively shallow with parent materials of sandstone, shale, or siltstone frequently within 10 to 20 inches (41-51 cm) of the surface. The needle-and-thread grass-plains muhly (Muhlenbergia cuspidata)-carex (Carex duriuscula and C. filifolia) type has extremely shallow soils with bedrock, gravel, or scoria close to the surface, pH between 7.2 to 8.9, and percentages for sand, silt, and clay are 46, 19, 35, respectively. The big bluestem-porcupine grass-prairie dropseed (Andropogon gerardii-Stipa spartea-Sporobolus heterolepis) occupies shallow soils with an average pH of 7.3. Soils were 64% sand, 24% silt, 15% clay [136].
Livestock: The early green foliage of Lewis flax is sought out by livestock [61,62]. However, domestic sheep are reported to have been poisoned by grazing on Lewis flax, which has been shown to contain a cyanogenetic substance (capable of making cyanide) [1,42]. Dittberner and Olson [35] also list Lewis flax as a plant suspected to be poisonous to livestock.
Big game: The early green foliage of Lewis flax is readily eaten by elk, mule deer, white-tailed deer, and pronghorn [10,55,61,62,82,89,100].
A study done at the Desert Experimental Range of the Intermountain Forest and Range Experiment Station, Utah revealed that Lewis flax has a high preference rating as antelope forage and is generally used during the summer and fall. The preference rating was higher during wet years versus dry years because in wet years there is a greater abundance of Lewis flax available [14].
Birds: The seeds of Lewis flax are sought out by birds during the fall and winter months [61,100,121]. It is desirable for sage-grouse and Columbian sharp-tail grouse habitat [113].
Other small mammals: Lewis flax is "never edible" to golden-mantled ground squirrel, and "seldom edible" to the least chipmunk in trapped and caged populations taken from a rocky, meadow habitat in the mountains of west-central Colorado [29].
Feeding trials with trapped deer mouse populations revealed that Lewis flax seeds were preferred, and comprised of 16.3% of their diet. The deer mice were trapped in big sagebrush-antelope bitterbrush (Artemisia tridentata-Purshia tridentata), singleleaf pinyon-Utah juniper, and Jeffrey pine-snowbrush ceanothus (Ceanothus velutinus) vegetation types in western Nevada. Preference rating (scale of 1 to 18) for Lewis flax seeds for each vegetation type were 6, 7, and 8, respectively [45].
Conversely, Addicott [1] states that the fruit of Lewis flax seems to be avoided by birds, small mammals, and insects.
Palatability/nutritional value: Lewis flax generally has fair palatability to livestock and big game [121]. Palatability of Lewis flax for several western states has been rated as follows [35]:
Colorado Montana North Dakota Utah Wyoming Cattle fair fair fair poor fair Domestic sheep fair fair fair fair fair Horses fair fair fair poor fair Elk ---- poor ---- fair poor Mule deer ---- poor fair fair poor Pronghorn ---- ---- good fair fair White-tailed deer ---- ---- poor ---- poor Small mammals ---- poor ---- fair fair Small nongame birds ---- poor ---- fair good Upland game birds ---- poor ---- fair poor Waterfowl ---- ---- ---- poor poorCover value: Wildlife cover values of Lewis flax for some western states are presented below [35].
Colorado North Dakota Utah Wyoming Elk ---- ---- poor poor Mule deer ---- poor poor poor Pronghorn ---- poor poor poor White-tailed deer ---- poor ---- poor Small mammals ---- ---- fair poor Small nongame birds fair ---- fair poor Upland game birds ---- ---- fair poor Waterfowl ---- ---- poor poorLewis flax normally requires 2 to 3 years to establish, mature, and flower [114]. Wasser [131] states that it might begin to flower by the 3rd year or, under more favorable conditions, by the end of the 2nd. Lewis flax maintains some green basal foliage year-round [117].
Lewis flax flowering periods were studied for 8 years in Saskatchewan. The mean first-flower date was June 5. The earliest flower date was May 19 and the latest was June 19. The latest date a plant was in flower was recorded as July 27. The mean flowering period was 33 days [26]. The following table provides flowering dates for Lewis flax.
State, Region, Province Anthesis Period Arizona March to September [69] California May to September [91] Nevada April to August [16,68] West Virginia June and July [122] Baja California March to September [138] Pacific Northwest May to July [60] Canada late May [32]Lewis flax seeds mature in late July and August [117].
Lewis flax is likely to survive and sprout from the caudex after fire, although no direct observations of this are reported in the literature.
Anecdotal information provided by Wasser [131] indicates that Lewis flax may establish from seed after fire. Lewis flax was present on burned sites and not on unburned sites in blackbrush communities in southern Nevada [24], suggesting that it recovers from an off-site seed source or from soil stored seed. Lewis flax seeds are capable of surviving in the soil for "multiple" years [73], so it is possible that Lewis flax may recover from the seed bank after fire. However, further research is needed on how Lewis flax seeds respond to fire.
Lewis flax regenerates from seed and by sprouting from the caudex [85,117].
Pollination: Lewis flax is pollinated by flies, bees, and other insects in Colorado [1,70,71]. In western North Dakota populations, bees and flies were the most common visitors [79]. It is also probable that Lewis flax is wind pollinated [92].
In montane habitats above 9,100 feet (2,800 m) at the Rocky Mountain Biological Laboratory in Colorado, flies were more common than bees as pollinators of Lewis flax. Bees are more effective than flies at depositing pollen, but mean bee visitation of Lewis flax was lowest at the high-elevation site in all years. The lower number of bee visits at higher elevation sites could be because the dilute nectar available from Lewis flax flowers is less attractive than the nectar-rich flowers of other species that occur in alpine areas, or because there is a decrease in the number of solitary bees at high elevations [70,71].
Pollen-eating muscoid flies are common pollinators of Lewis flax in Colorado. One Lewis flax flower produces fewer than 3,500 grains of pollen during the 1-day flowering period. These flies are known to eat more than 1,000 grains in a day and could have a negative impact on plant paternal fitness [71].
Breeding system: Lewis flax is a self-fertile homostylous species. Most species in this group are obligate outcrossing perennials [70,71].
Seed production: The spherical capsules of Lewis flax produce up to 10 seeds each. Many seeds are immature upon dispersal and must undergo an afterripening period before germinating [111,117].
Although Lewis flax is self-compatible, pollination by insects is needed for seed production [70,71]. In her study on the role of fly pollination in montane habitats, Kearns [71] grew 5 Lewis flax plants under laboratory conditions. The plants received no pollination treatments or insect visits. The 5 plants produced 438 flowers, none of which produced fruits with seeds [71].
Lewis flax seed set differed significantly (p = 0.0001) among low-, mid-, and high-elevation sites and among years (P = 0.03). Seed set decreased with increasing elevation. The lower seed set at higher elevations could be due to pollen limitation (see Pollination) or could be due to the shorter growing season and extreme weather conditions in alpine areas [71].
A study of Lewis flax plants transplanted from steppe and forest communities above the Yukon River at Eagle, Alaska indicates that light and water availability affect Lewis flax seed production. Reproducing individuals grown in the shade had an 87% reduction in total seed biomass. An increase in light significantly (P ≤ 0.05) affected seed production. Total seed biomass increased nearly fivefold with added moisture and was significant at the P ≤ 0.01 level [134].
Seed dispersal: No information is available on this topic.
Seed banking: Seed banking and longevity under field conditions have not been well studied for this species, although Kitchen [73] suggests that seeds survive for "multiple" years. Evidence of an afterrippening period for Lewis flax seeds (see Germination) suggests that they may remain viable in the soil for extended periods; however, further research is needed on the seed banking capabilities of Lewis flax.
Germination: Many Lewis flax seeds germinate in 10 to 15 days indoors at 60 to 70 °F (16-21 °C), and in 15 to 30 days in the field, under variable moisture and temperature conditions [131]. Lewis flax seeds taken from a high mountain grassland study site in western Colorado were germinated in a greenhouse setting. The optimum temperature regime for seed germination was 59 °F (15 °C). The cumulative percentages for Lewis flax seeds that germinated are presented below [93].
Observation days
7 14 21 28 35 Cumulative percent germination 16 80 86 86 86Duration and climatic conditions of storage affect germination rates of Lewis flax [21,66,74] and suggests that Lewis flax is able to germinate under variable conditions. Jorgensen and Wilson [66] revealed that Lewis flax seeds germinated in the dark at 34 to 38 °F (1.1- 3.3 °C), and had a mean germination rate of 55% at ~35 days and 75% at ~55 days. A germination study using Lewis flax seeds from 21 Utah, Idaho, Nevada, and Washington populations found that percent germination for seeds recently harvested was 17% to 100% with no prechill period (control), 28% to 100% for seeds that underwent a 28-day prechill period, and 32% to 100% for those with a 168-day prechill period [74]. These results suggest that average germination of Lewis flax seeds increases the longer they are prechilled. Conversely, greenhouse germination trials revealed that the greatest percent germination of Lewis flax seeds occurred after being stored dry, at room temperature. There was a decrease in percent germination for seeds stored in dry, cold storage and wet, cold storage. The seeds used in the trials were collected during the summer on western North Dakota native ranges. The storage period for all treatments began December 1, and germination tests began on the 10th of each month and were observed for 60 days. The percent germination of Lewis flax seeds is presented below [21].
Month
January February March April May Dry-room temperature storage 16 23 36 33 79 Dry-cold storage 4 25 16 13 43Wet-cold storage
14 25 1 41 20Lewis flax seeds may have an afterripening period, in that they initially exhibit low germination rates that increase after a period of storage [21,66,74]. Lewis flax germination was recorded, over a 25 year period, for seeds stored in an open, unheated, and uncooled warehouse. Greatest germination occurred after 5 years of storage. Percent germination of Lewis flax seeds after 2 to 25 years of storage in an open warehouse are presented below [115].
Years of Storage
2 3 4 5 7 10 15 20 25 Percent germination 66 72 85 93 83 70 25 8 0Seedling establishment/growth: The seed coat of Lewis flax seed is mucilaginous (secretes a gelatinous or gummy substance). The mucilage adheres to the soil when hydrated, resulting in seed retention on site [30] and allowing for establishment on bare soil. Lewis flax seedlings have a thin, vigorous root, 1/3 to 1/2 the length of the hypocotyl [17]. Seedlings are vigorous, and have a rapid growth rate [87].
Leachates from singleleaf pinyon (Pinus monophylla) and Utah juniper (Juniperus osteosperma) litter may inhibit Lewis flax seedling establishment. In a greenhouse study, buried seeds emerged more frequently from mineral soil than from pots with singleleaf pinyon and Utah juniper litter. When Lewis flax seeds were broadcast seeded, emergence was greater on singleleaf pinyon litter than on either Utah juniper litter or mineral soil [44]. Everett [44] speculates that allelopathic effects of pinyon litter on broadcast seeds are offset by improved surface microenvironment and reduced seed desiccation.
A seedling establishment study done in southwestern Colorado's San Juan Basin Research Center reports that Lewis flax seedlings have a better chance of establishing if seeds are planted in fall rather than spring. Three separate plantings were done in April, May, and October of the 1st year, and in May, June, and October of the 2nd year. Establishment ratings were assigned to the stands based on visual observations made in May of the following year. Lewis flax seedling establishment was higher for October plantings than spring plantings in both years. Establishment ratings are summarized below [47].
Date of planting Establishment rating* 1982 April 16 1.13 May 17 1.83 October 21 3.751983
April 20 1.00 June 9 1.63 October 17 3.60 * 1=1% to 25%, 2=25% to 50%, 3=50% to 75%,Asexual regeneration: Lewis flax sprouts from the caudex [85].
Lewis flax is a pioneer, early-, and late-seral species in mountain brush, pinyon-juniper, and ponderosa pine (Pinus ponderosa) communities of the Intermountain West [118,129]
Lewis flax is 1 of the forbs with highest frequency on a 40- to 50-year-old burn in west-central Montana. Douglas-fir, lodgepole pine, and quaking aspen were representative small trees regenerating on this site [106].
The scientific name of Lewis flax is Linum lewisii Pursh (Linaceae) [3,33,39,40,59,67,68,69,122,138].
Perennial blue flax (L. perenne) is a distinct, closely related species that is native to Europe [97,98]. It was once considered a synonym for L. lewisii [50,60,133].
Lewis flax is commercially grown and planted throughout the Intermountain West [117]. It is used in the reclamation of mining sites and spoils, roadsides, and construction sites [23,25,34,61,62,108]. Germination of Lewis flax seeds directly seeded into coal mine spoils at Dickenson, North Dakota was successful, and resulted in 43 seedlings/m² after 120 days. This is a low number, however, compared to other species that had over 300 seedlings/m² [21]. Another reclamation study on coal mine spoils in North Dakota groups Lewis flax with plants described as "showing excellent establishment characteristics, even though they did not make outstanding height growth or provide exceptionally good cover." It was also noted that Lewis flax "appeared to show little promise because of low germination and/or survival for use in revegetation trials on spoil bank material" [20].
Lewis flax is a desirable species to seed for rehabilitation of rangelands and shrublands [85,129]. Transplanting Lewis flax is usually very successful and establishment can be expected when proper transplanting techniques are used [112]. In arid climate landscapes, the heat/drought-tolerant Lewis flax can be a substitute for plants that require more water [54]. Its ease of establishment is noted as "excellent" [85]. However, because Lewis flax seeds are eaten by deer mice in some vegetation types, they may not be appropriate to use in seed mixes. Everett, Meeuwig, and Stevens [45] suggest not using highly preferred seeds in some seed mixes, planting desirable species whose seeds are not preferred by deer mice, or treating desirable seeds with a repellent.
Lewis flax shows low potential for use in revegetation of subalpine sites or wildlife habitat improvement in Colorado [121,131].
Nonnative Species: Lewis flax is a strong competitor against spotted knapweed (Centaurea maculosa). A common garden experiment at The University of Montana Diettert Experimental Gardens in Missoula, Montana, revealed that aboveground biomass of spotted knapweed was lower (~1 g) when planted with Lewis flax versus spotted knapweed grown alone (~4.5 g). Fungicide added to the soil did not affect Lewis flax growth or how Lewis flax interacted with spotted knapweed [28].
When seeded in mixtures into cheatgrass (Bromus tectorum)-dominated communities, Lewis flax establishes and spreads quickly, occupying both open areas and those dominated by annual weeds [117].
Linum lewisii (Linum perenne var. lewisii) (Lewis flax, blue flax or prairie flax) is a perennial plant in the family Linaceae, native to western North America from Alaska south to Baja California, and from the Pacific Coast east to the Mississippi River.[2] It grows on ridges and dry slopes, from sea level in the north up to 11,000 feet (3,400 metres) in the Sierra Nevada.[3][4][5]
It is a slender herbaceous plant growing to 80 centimetres (31+1⁄2 inches) tall, with spirally arranged narrow lanceolate leaves 1–2 cm (1⁄2–3⁄4 in) long. The flowers are pale blue or lavender to white, often veined in darker blue, with five petals 1–1.5 cm long.[5][6][7][8] The flowers open in the morning and fade, dropping their petals by noon on hot, sunny days.[9]
The plant was named for North American explorer Meriwether Lewis.[10]
Blue flax is a durable wildflower in garden conditions, never becoming overly aggressive towards other plants. Plants are easily grown from seed.[9] Blue flax grows well in lean soils without much organic matter and are healthier in well drained soils.[11]
The inflorescence is a terminal open racime.[7]
Flowers are pale blue or lavender to white, often veined in darker blue, with varying-length styles.[6]
Leaves are lanceolate, spirally arranged, 10–30 mm (0.4–1 in) long.[7]
Linum lewisii (Linum perenne var. lewisii) (Lewis flax, blue flax or prairie flax) is a perennial plant in the family Linaceae, native to western North America from Alaska south to Baja California, and from the Pacific Coast east to the Mississippi River. It grows on ridges and dry slopes, from sea level in the north up to 11,000 feet (3,400 metres) in the Sierra Nevada.
It is a slender herbaceous plant growing to 80 centimetres (31+1⁄2 inches) tall, with spirally arranged narrow lanceolate leaves 1–2 cm (1⁄2–3⁄4 in) long. The flowers are pale blue or lavender to white, often veined in darker blue, with five petals 1–1.5 cm long. The flowers open in the morning and fade, dropping their petals by noon on hot, sunny days.
The plant was named for North American explorer Meriwether Lewis.