This description covers characteristics that may be relevant to fire ecology and is not meant for identification. Keys for identification are available (for example, [53,68,137,162,193]). Morris and others [122] provide a key for identifying American plum and other shrubs in winter.
Morphology of woody parts: American plum's form is usually shrubby [70,186,187], but it may grow as a small tree. It ranges from 3.3 to 33 feet (1-10 m) tall [69,90,157,165] tall. It is likely to grow tallest and assume tree form in its southern distribution [76]. American plum usually grows as a small, single-stemmed tree in southern Alabama, Georgia, and Florida [53]. American plum trees have short, crooked trunks with stiff lateral branches that form wide, flat-topped, irregular crowns [70]. Tree trunks may reach 12 inches (30 cm) in diameter [70]. Crowns are spreading [37]. The national champion tree is 18 feet (5.5 m) tall, 3.8 feet (1.1 m) in diameter, and 18 feet in spread; it grows in Fairfax County, Virginia [5]. American plum wood is moderately heavy and hard [46,70,104]. Bark is "moderately" thick [115]. Some to all [31,33,58] branches are spurred [31,69,114,187], becoming more so with age [46]. Bottom branches typically grow low to the ground [46]. American plum is commonly infected with a fungus that produces black swellings on the twigs [186]. Root structure is not well known for American plum [117]. A few researchers found American plum had shallow [90,117,159], spreading [159] roots. A root-profile study of clay prairie soils in Fargo, North Dakota, found most American plum roots were in the 1st foot (0.3 m, 40% of roots) or 2nd foot (0.6 m; 33% of roots) of soil. Maximum root depth was 6 feet (2 m) [195]. A 15-year-old shrub in eastern Nebraska had roots extending 2.5 feet (0.8 m) deep. Lateral roots ranged from 2.5 to 11 feet (3 m) long [159].
Leaves and reproductive structures: American plum is deciduous [150]. Leaves are narrow with sharp teeth; they are 3 to 5 inches (8-13 cm) long [70]. Flowers and fruits grow on short spur shoots [68]. The inflorescence is an umbel with 2 to 4 flowers [27,69,114,157,187]. The flowers are strongly fragrant [53,90,157] and showy, about 1 inch (2.5 cm) across [70]. Fruits are yellow or red drupes [27,52,53,69,137,157], 0.8 to 1.3 inches (2.0-3.2 cm) in diameter [157]. They may be solitary or in clusters [157]. The seed is a smooth, compressed stone [27,114,157].
Stand structure and age class: American plum often forms thickets [31,46,69,74,104,137,157,186,187] that are sometimes dense [104,160]. Structure of American plum stands along moist areas in eastern Colorado has been described as "dense, almost impenetrable thickets" in a "dense, thorny mass" [83]. American plum thickets in Kansas are up to 35 feet (m) wide [81]. Thickets spread from root sprouts.
American plum is short-lived [167]. Shrubs in Nevada live about 20 years (Cristner 1966 personal communication in [160]). Because American plum clones, American plum thickets can persist long after the original parent stems have died [46,48].
American plum is the most broadly distributed wild plum in North America [41,75]. It occurs from southern Saskatchewan east to southern Quebec and southern Maine and south to Arizona and central Florida [70,82,106,125]. Its core distribution extends from Minnesota east to Rhode Island and south to central Oklahoma and north-central Florida. Populations become increasingly isolated outside this core area [105], with extremely isolated plants in Washington [82]. American plum is native to North America, but its native range is unclear. Its core range may approximate its distribution before European settlement [41]. Human plantings have expanded American plum distribution; American plum is often planted outside its core range [40,104] and sometimes escapes cultivation [70,104,182]. It is likely nonnative in Washington, Oregon, California, Idaho, Nevada, and Texas (review by [46]). Some claim American plum does not occur in Texas [82,105], but it has been documented in East Texas [183] and has been planted and has probably established elsewhere in the state (review by [46]). American plum is nonnative in Quebec [125] and likely in other Canadian locations [70]. Native Americans may have introduced American plum in the Great Plains before European settlement ([90], review by [46]). American plum's native status is uncertain in the Intermountain West [27]. Pioneers introduced American plum in Utah, but American plum may have already been present in some parts of the state [187]. The US Geological Survey provides a map of American plum's North American distribution.
American plum is planted in temperate regions throughout the world, and has likely established outside North America [46].
Prunus × orthopsepala occurs in Kansas [82].
Although American plum is an unlikely woody pioneer in prairie communities, it may establish after woody pioneer species such as roughleaf dogwood have invaded prairie communities. Based on the prescribed fire and fire history studies discussed above, prescribed fires at intervals of ≤20 years may control invasion of woody species onto grasslands. Effects of fire on American plum and other woody-draw species vary with different combinations of fire frequencies, substrates, topographies, and climate [11,72]. Kucera and others [87] advise that on productive sites, prescribed fires timed at intervals that allow for "maximum" fuel buildup control woody plants in grasslands most effectively. Managers will likely find that responses of woody species, including American plum, to prescribed fires are site- and season-specific [174].
Although some woody species are invading some prairie sites, woody draws imbedded within prairies and oak/grassland communities are declining in other areas [30,50,191]; in part, this decline is likely due to fire exclusion. In white oak-black oak woodlands of the Morton Arboretum, Illinois, general decline of understory shrubs and extirpation of American plum are attributed to fire exclusion. The area was near a Potawatomie village prior to European settlement, and the Potawatomie apparently burned areas just adjacent to the village annually and areas near the village frequently [191]. In Badlands National Park, South Dakota, "most, if not all" woody draws are decadent or showing no regeneration of woody species, with attendant declines in productivity and nutritional quality of browse. American plum is a common but declining species in woody draws in the Park [30].
For wooded areas needing management intervention, prescribed fire may help open up shrub thickets or rejuvenate declining stands through postfire sprouting of woody species [150]. Restoring fire in Badlands National Park is identified as a critical management goal. Dingham and Paintner [30] recommend early spring or summer fires for wooded draws of Badlands National Park; they provide a set of fire management and monitoring goals for the area.Ecosystems in which American plum is most common—including oak savannas and woodlands and elm-ash and shrubland draws imbedded within prairies—historically experienced mostly low- and mixed-severity fires from approximately 4- to <100-year intervals, with intervals of less than 40 years most common [92,93,94,95,96]. Limited information suggests that oak communities [131] and woody draws within short- and tallgrass prairies [150] historically burned mostly in late summer and fall. Estimated fire-return intervals averaged 4 to 5 years for oak savannas [92,94], 5 to 11 years for oak woodlands [93,96], 55 years for oak-ash woodlands [95], and 40 to 45 years for woody draws [91]. See Habitat Types and Plant Communities for descriptions of these communities.
In the absence of fire, woody species are encroaching onto Great Plains sites that were historically grasslands ([1,39,72,143,174], review by [181]). Comparing vegetation surveys done in eastern Nebraska from the mid-1800s with surveys done from 1979 to 1983, Rothenberger [143,144] found shrubs, including American plum, that grew along the margins of bur oak-bitternut hickory communities had expanded into remnant patches of tallgrass prairie with fire exclusion. Dense American plum thickets are common in the north-central Great Plains [162]. With fire exclusion, American plum is most likely to establish in woody draws in late succession. For example, American plum has expanded onto the western edge of big bluestem (Andropogon gerardii) tallgrass prairie with fire exclusion [117].
Data from the Konza Prairie demonstrate the effect of varying fire-return intervals on shrub cover in tallgrass prairie. Historically, the Konza Prairie is thought to have burned about every 4 years. Fires returned frequently enough to prevent woody species in draws from spreading onto the prairie. On little bluestem-indiangrass-big bluestem prairie, American plum did not occur on plots burned under prescription at 1-year or 4-year intervals; however, American plum seedlings had 32.5% frequency on plots that burned only once, in a wildfire, in 18 years. In 18 years of study, total shrub cover increased twice as much with 3-year fire-return intervals and on the wildfire-burned site than on the site burned annually. Burning at 4-year intervals resulted in the greatest increase in total shrub frequency (12.5%), while annual burning resulted in the smallest increase in shrub frequency (3.7%). Total shrub frequency increased by 10% after the single wildfire [63].
Historically, fires were likely less frequent in wooded draws than in oak savannas at that time because fuels in the prairie are finer, cure out earlier, and dry more quickly in response to hot, dry, windy weather than fuels in woody draws. Moister soil conditions in woody draws tends to extend the growing season past that of open prairies. Some woody draws are so steep-sided and deep that fast-moving prairie fires tend to skip over them (review by [155]). Some woody draws are in decline. Fire exclusion is likely a component of this decline [87], although grazing ([101,102], review by [84]), conversion of surrounding areas to croplands, and lowering of groundwater have also been implicated (review by [84]).
American plum is a mostly minor component in eastern hardwood and pine communities. See the Fire Regime Table for further information on FIRE REGIMES of these and other vegetation communities in which American plum may occur. Find further 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".
Plant response to fire: American plum sprouts from the roots after top-kill by fire [115,152]. Even small American plums sprout after top-kill [115]. American plum may also establish after fire from animal-dispersed seed [152] or from the seed bank [20], although postfire seedling establishment of American plum had not been documented as of 2010. American plum shows a trend of increasing after occasional fires and remaining stable or declining with frequent fires (annually or every few years).
Prairie communities: American plum apparently increased after fire in woody draws of North Dakota. Two years after a 1976 October wildfire near the Little Missouri River, North Dakota, American plum and chokecherry showed 2nd highest densities among shrubs in woody draws. Their combined density was about 5 times less than that of western snowberry. The fire burned a mosaic of green ash/western snowberry draws and western wheatgrass-little bluestem mixed-grass prairie. Overall, shrub densities in postfire year 2 were higher on burned than on unburned sites. Biomass of the 2 Prunus species was much greater on burned sites compared to unburned sites; increased biomass was due more to height gain than stem increases [196].
Mean density and estimated biomass of American plum and chokecherry 1 and 2 years after a fall 1976 wildfire. Data for the 2 species are pooled [196]. Burned Unburned 1977 (postfire year 1) Density (stems/m²) 5.8 no data Biomass (g/m²) 9.5 no data 1978 (postfire year 2) Density (stems/m²) 6.7 4.6 Biomass (g/m²) 76.5 0.3American plum cover remained stable and low with annual prescribed spring burning in Pipestone National Monument. Over 4 years, its cover increased from 0.4% the summer after the 1st fire to 1.3% the summer after the 4th fire [9]. Comparisons with prefire cover or unburned sites were not provided.
Frequent fire may reduce frequency of American plum and other woody species in tallgrass prairies and savannas. American plum cover was negatively correlated with fire frequency (r= -0.355, P=0.258) [172] on bur oak-northern pin oak (Q. ellipsoidalis) savannas in east-central Minnesota that were burned under prescription 2 to 19 times in 20 years (1964-1984) [171,172]. This followed a general trend of decreasing woody plant cover and increasing cover of native bunchgrasses with increasing fire frequency [172]. On the University of Missouri's Prairie Research Station, a 7 April prescribed fire reduced American plum and other woody vegetation more than a 31 March prescribed fire. The site was a big bluestem-little bluestem tallgrass prairie; woody species included American plum, American elm, eastern redcedar, and Arnold hawthorn (Crataegus mollis). Maximum age of woody vegetation was at least 8 years. Conditions were warmer and drier for the April fire than the March fire, with relative humidities of 21% and 43%, respectively. The March fire was conducted when it was cloudy and humid; rain fell by the end of the day. Overall, 90% of the woody plants were killed or top-killed by the April fire compared to 40% for the March fire. The fires top-killed most American plums; the April fire killed more small American plums than the March fire [87].
Percent of American plum stems present (mean number sprouts/root crown) in postfire month 3 by fire response class for a tallgrass prairie burned on 31 March 1962 or 7 April 1962 [87] Diameter (inches) of stems at 6 inches above ground Fire response class 0.0.5-0.5 0.6-1.5 1.6-3.5 All size classes March fire April fire March fire April fire March fire April fire March fire April fire Killed 0 0 0 6 0 0 0 6 Top-killed; sprouted 100 (10.0) 82 (4.1) 100 (6.) 94 (7.9) 0 50 (15.0) 86 86 Some surviving crowns; sprouts present or absent 0 18 (2.0) 0 0 100 (2.0) 50 14 8Tree-dominated communities: In southeastern Missouri, a 7 May 1966 wildfire apparently favored American plum in a 23-year-old white oak-northern red oak-hickory stand that had developed after a 1943 fire. Some vegetation analysis had been conducted prior to the 1966 wildfire for woody plants ≥0.6 inch (1.5 cm) DBH; American plum was not noted on those plots. Ten years after the 1966 wildfire, American plum showed 2% frequency and a density of 64 stems/ha. American plum's basal area comprised <0.1% of total basal area. Total shrub abundance was greatest in postfire year 3, with shrub production lowering "markedly" by postfire year 5 [107].
Thinning from below followed by frequent prescribed fire reduced American plum density on an Arkansas pine plantation. The sites were on an old field planted to loblolly pine and shortleaf pine 49 years prior to the study. Sites were thinned and burned in winter, followed by annual summer prescribed fire on sites where fuel build-up and weather allowed burning. Seven years after thinning, American plum density was 41 stems/acre on burned plots and 125 stems/acre on unburned plots [24].
American plum seeds require a long stratification period [3,35,49,79,169], typically overwintering in the seed bank (review by [46]). American plum seeds need 60 to 150 days of moist stratification to germinate in the laboratory ([3,169], reviews by [8,46,152]). In the field, American plum seeds probably require stratification in continuously moist substrate for germination. In xeric areas, those conditions are likely only along moist drainages with litter [35].
Although animals disperse the seeds, it is unclear if ingestion, mechanical scarification of seeds, or mechanical removal of fruit aids germination. A study on the Crab Orchard National Wildlife Refuge, Illinois, showed American plum germination was reduced by passage through coyote intestinal tracts [28], but a laboratory study found that acid treatment had no effect on American plum germination rates [169]. Removing the fruit's pericarp and endocarp improved germination in one laboratory study [35] but reduced germination slightly in another [49].
Germination is hypogeal (review by [46]). Germination rates average 70% in laboratory studies ([79], review by [152]). Laboratory studies suggest that temperature requirements for germination may vary by site or population, with northern populations germinating at lower average temperatures than southern populations. American plum seeds from Minnesota showed maximum germination rates (86%) when stratified at 50 °F (10 °C) for 60 days [142], while seeds from Nebraska germinated best at 80 °F (27 °C) after 60-day stratification [169]. A review stated mineral soil provides the best seedbed for American plum [160].
Soils: Soils supporting American plum are generally nutrient-rich [70] and deep (review by [152]).
Texture and chemistry: American plum prefers medium- to coarse-textured, acidic to mildly alkaline soils [65]. It grows in sandy to loamy soils in the Intermountain West (review by [152]) and sandy loams and fine sandy loams in the Great Lakes states [85]. In southeastern Michigan, it grows in coarse-textured, well-drained soils [6,33,182]. It grows in rich, often calcareous loams in the Southeast. A laboratory test found American plum seeds were moderately tolerant of alkaline conditions [164]. Some report American plum as slightly tolerant of saline soils (review by [152]); however, a laboratory study found American plum seedlings watered with a nutrient solution with salt showed poor survivorship compared to seedlings watered with a nutrient solution without salt. The authors recommend against growing American plum in saline soils [173].
American plum is reported on alluvium in Ontario [157].
Moisture: American plum grows on sites receiving at least 16 inches (40 cm) of annual precipitation (review by [152]). In the arid West, American plum is mostly restricted to mesic and moist areas including riparian zones [31,112,114], ditch banks, moist field edges, and moist foothills [86,104,116,119,122,150]. It is reported on mesic areas such as drainages in Fort Union Basin, Wyoming [35]. American plum occurs in ravines, coulees, and drainages in Great Plains shrublands of Bighorn Canyon National Recreation Area ([86], review by [46]). Weaver [184] found that in Nebraska, shrubland sites with and without American plum had higher percentages of soil moisture, higher humidities, and lower summer temperatures than prairie sites. In eastern North America, American plum grows most often on moist sites [52]. It is reported on moist sites in Ontario [157]. In Florida, it grows on mesic hammocks and floodplains [194].
In areas with high average annual precipitation, American plum sometimes occurs on sites that dry in summer. In southeastern Michigan, American plum is an indicator species of very dry black oak sites [6]. It grows on moist to dry areas in the Pacific Northwest [69] but is more common on moist sites [13,33,52,112].
Topography and elevation: Topography on sites with American plum may be flat to steep. American plum is distributed from the plains to low mountains in the Pacific Northwest [68,69]. It is common in canyons in the Black Hills [31]. In the Great Plains, it grows in draws [185] and sheltered depressions within prairies [76]. It grows on slopes and outwash mesas and in gullies and valleys in Colorado [58,186] and New Mexico [114].
Few elevational ranges were reported for American plum as of 2010. It grows at high elevations in the Southwest.
Area Range (feet) Colorado 3,500-6,000 [58] Arizona 5,000-7,200 feet [104] New Mexico 4,000-7,500 [104,114] Appalachians ≥3,600 [33]Climate: American plum has good cold tolerance [152] but cannot withstand prolonged drought [184]. Its distribution extends into the -40 to -30 °F (-40 to -30 °C) cold-hardiness zone [40,73]. In a Minnesota common garden, American plum cultivars were the most cold-hardy among 7 Prunus species or hybrids. The minimum temperature used to induce flower bud drop in the Prunus collection, -21 °F (-29 °C), caused no damage to American plum flower buds [32]. American plum seedlings showed poor survivorship when transplanted on dry sites during the "Dust Bowl" drought of the 1930s [48].
Wooded draws of the Northern Great Plains and oak-hickory woodlands throughout their distribution provide critical habitat for wildlife, and American plum is an important component of these ecosystems. Although woody draws occupy about 1% of the Northern Great Plains landscape, many bird and small mammal species use them extensively. White-tailed deer and cattle also seek out these draws [154]. Johnston and Odium [77] describe breeding bird use of successional stages of oak-hickory forest on the Georgia Piedmont (see Successional Status). The grass-shrub stage, which included American plum, is the primary breeding habitat of 7 passerines [77].
Many herbivores including white-tailed deer [74], mule deer [89], and cottontails [81,156] browse American plum. On the Konza Prairie in Kansas, white-tailed deer browsed American plum more than expected based on availability [178]. In eastern Montana, common porcupines browsed American plum stems lightly in winter [64]. American plum is apparently not heavily used by wildlife in Arkansas [74].
Many birds and mammals eat the plums ([26,162], review by [160]), including sharp-tailed grouse [67], squirrels [33], white-tailed deer [33,158], foxes [28,74], coyotes [28,43,110], northern raccoons [33,74,147], and America black bears [33,74].
American plum is a nectar plant for bees and butterflies ([82], review by [46]) and a pollen plant for bees [82].
Palatability and/or nutritional value: American plum browse is moderately palatable to white-tailed deer [7,122], mule deer [122], and wildlife in general [175]. Its palatability for big game in Utah is rated good overall, showing moderate palatability in spring and good palatability in summer and winter [134]. American plum is preferred by domestic goats on prairie remnants in northwestern Illinois [16]. Its palatability is rated poor to fair for cattle [166].
American plum browse on a woodland clearcut in Alabama had moderate protein levels and high digestibility. See Burton and Scarfe [22] for detailed nutritional analyses of American plum browse.
Ripe American plum fruits are sour [33,40,90] to sweet-tart [40,83] or sweet ([162], review by [46]). Plums in the East are generally more sour than fruits in the West [41], lending credence to the idea of human-aided dispersal of American plums to the west. Plums collected in South Dakota tested high in antioxidants [2].
Cover value: American plum thickets provide thermal and hiding cover (review by [152]) for many bird and mammal species ([76,124,127,145], review by [46]). American plum provides nesting cover for many bird species [76], particularly those preferring edges or thickets [127]. Sharp-tailed grouse use American plum for winter cover [67,136]. In eastern Montana, sharp-tailed grouse used wooded draws with American plum as fall and winter habitat more than expected based on availability [168]. In mountainous regions of Missouri, ruffed grouse were positively correlated with young (7-15 years old), regenerating clearcuts of mixed hardwoods, including American plum (r=0.71, P=0.02) [190]. On the Custer National Forest in eastern Montana, wild turkeys used green ash-box elder/fleshy hawthorn-American plum communities for fall and winter cover. A few hens used the community in spring for nesting [78]. In south-central South Dakota, wild turkey hens used American plum thickets for nesting cover, building nests beneath individual American plum shrubs [188].
In Lory State Park, Colorado, female mule deer used mixed-shrub thickets, where American plum codominated, less than expected based on availability during the day and at sunset. Their use was neutral (as much as expected) at night and at sunrise. For feeding and resting cover, mule deer preferred a mosaic of grassland interspersed with dense smooth sumac stands [88]. In green ash-American elm-boxelder communities along the Big Sioux River in South Dakota, American beavers preferred dense riparian vegetation on ungrazed sites to thinner vegetation on sites with cattle. American plum was among the understory species providing dense riparian cover [29].
Woody draws with American plum provide shade for livestock [150,166], although livestock may be unable to access dense American plum thickets.
American plum is mostly a woodland species, growing in mixed-hardwood communities and on woodland ecotones [112,157,182]. It also grows in shrublands and rarely, on open prairies. It often establishes in riparian zones [29,182]. It occurs on stream [31,58,70,114,157,182], pond, and lake boarders [182] and on swamp ecotones [70].
Midwest:
Woodlands:
American plum is common in oak (Quercus spp.) woodlands and savannas. It occurs in black oak-New Jersey tea (Q. velutina-Ceanothus americanus) communities of southeastern Michigan [6] and in post oak-blackjack oak (Q. stellata-Q. marilandica) woodlands of the Northeast and Great Plains [146]. An 1846 account of Illinois vegetation noted American plum in blackjack oak-black oak-big bluestem (Andropogon gerardii) savannas but not in woodlands or on open prairies [129]. American plum is a common understory species in bur oak (Q. macrocarpa) woodlands [34]. A1927 survey in the Black Hills of South Dakota showed American plum was subdominant in the bur oak-skunkbush sumac-smooth sumac (Rhus trilobata-R. glabra) montane association on the eastern foothills; the bur oak woodland was between lower-elevation mixed-grass prairie and higher-elevation interior ponderosa pine (Pinus ponderosa var. scopulorum) forest. These bur oak woodlands occurred in discontinuous bands along streams and in valleys [62]. On the Konza Prairie of Kansas, American plum grows in the understories of bur oak-chinkapin oak-American elm (Q. muehlenbergii-Ulmus americana) woodlands [47]. It occurs in oak-hickory forests of eastern Nebraska [185] and is an associated species in bur oak-bitternut hickory (Carya
cordiformis) communities along the Missouri River [4].
American plum occurs in elm-ash-cottonwood (Ulmus-Fraxinus-Populus spp.) draws within and bordering short-, mixed- [12,13,51,76], and tallgrass [76,129] prairies. It is common in green ash (Fraxinus pennsylvanica)-American elm woodlands in the Northern Prairie region [23]. In eastern Montana, it is a component in tall shrub layer of white ash/chokecherry (Prunus virginiana) upland-hardwood associations [100,101]. American plum occurs in American elm-bur oak/fireberry hawthorn (Crataegus chrysocarpa var. chrysocarpa) communities of the Williston Basin, North Dakota [12] and in green ash-American elm-boxelder (Acer negundo) communities along the Big Sioux River in South Dakota [29].
In Nebraska, it grows on the margins of cottonwood/willow (Salix spp.) gallery forests [185].
American plum grows in quaking aspen (P. tremuloides) communities in Minnesota and Wisconsin [85].
American plum grows in a few conifer woodlands. A late 1800s survey in Nebraska found American plum was associated with interior ponderosa pine-eastern redcedar (Juniperus virginiana)-bur oak communities in canyons and along rivers [17]. American plum is also an associated species in Rocky Mountain juniper (J. scopulorum) woodlands in some parts of Rocky Mountain juniper's range ([179], review by [66]).
Shrublands:
American plum is common to dominant in woody-draw shrublands of the Great Plains [185]. In Lory State Park in western Colorado, American plum was codominant in "very dense" thickets along draws. Fragrant sumac (R. aromatica), cerro hawthorn (C. erythropoda), and chokecherry also codominated [88]. In eastern Nebraska, American plum was subdominant in smooth sumac-American hazel (R. glabra-Corylus americana) communities. These communities occur along wooded draws of the Missouri and Niobrara rivers [4]. Nebraska shrublands vary from a few yards to more than 0.5 mile (0.8 m) wide. Shrubs may finger into the understory of adjacent oak-hickory (Quercus-Carya spp.) forests in the eastern Great Plains [184,185].
Prairies:
American plum is sometimes important in mixed wheatgrass-bluestem-needlegrass (Tritiacea-Andropogonacea-Stipeae) prairies of the Great Plains [189], but it is generally infrequent on open grasslands (see Successional Status).
Other regions:
American plum is less common in the Intermountain, northeastern, and southeastern regions than in the Great Plains. In the Intermountain region, American plum grows on deep, moist soils within mountain brush [121,152], pinyon-juniper (Pinus-Juniperus spp.), and sagebrush (Artemisia spp.) zones (review by [152]. As of 2010, there was little information on specific plant communities of the Northeast and Appalachian regions with which American plum is associated. American plum is associated
with Shumard oak (Q. shumardii) "shinneries" on the Atlantic Coastal Plain [108]. In the Southeast, it grows in mesic hammocks and on floodplains [53,194]. Information on historical frequency of American plum in southeastern pine
(Pinus spp.) and hardwood forests is sparse. Surveys by early settlers in longleaf pine (P. palustris) forests of Alabama found American plum comprised less than 1% of the tree subcanopy. American plum's occurrence as a shrub was not noted [135]. Surveys in the early 1900s in northern Florida reported American plum as rare in upland oak-gum (Quercus-Nyssa
spp.) hardwood forests [149].
Vegetation classifications listing American plum as a dominant species are listed below.
American plum is intolerant of heavy browsing and trampling [103]. On green ash draws on the Missouri Plateau of South Dakota, American plum cover was greater on moderately grazed than heavily grazed cattle rangelands [50]. Five years after felling and planting of wooded draws in southwestern North Dakota, American plum was much more frequent on sites without cattle grazing (70% survival of sprouts and/or seedlings) than on grazed sites (11% survival of sprouts and/or seedlings) [177]. American plum may tolerate moderate grazing levels. In green ash draws in the Badlands of North Dakota, density of American plum saplings and trees was higher in moderately grazed plots (28.4 stems/ha) than in lightly grazed (8.2 stems/ha) or heavily grazed (1.6 stems/ha) plots. Study sites were stocked with cattle [23].
In northwestern Illinois, domestic goats were used to help control woody species on prairie remnants where prescribed fire was not feasible. The animals helped reduce many woody species, including American plum. See Blackmore [16] for details of the study
and suggestions for managing domestic goats on prairies.
Contemporary use: American plum is a culinary plant [33,37,40,82]. It is cultivated for fruit [27,40,74] and as an ornamental [25,40,70], but it is not usually grown in commercial orchards [70]. Over 200 forms of American plum have been selected for cultivation, and American plum has been extensively hybridized with commercial plum cultivars [104]. It is sometimes used as rootstock plant for cultivated Prunus species ([57], review by [73]), but its tendency to root sprout means it is not ideal rootstock material (review by [73]).
Traditional use: American plum was used extensively by Native Americans [82,166]. Havard [61] speculates that Native Americans were cultivating American plums near villages before the arrival of Europeans. The Pima of Arizona and Mexico cultivated American plums since at least the period of Hispanic occupancy (1600s to mid-1800s) [139]. The Cheyenne ate the plums fresh, dried, and cooked in desserts. Fruits were also used in medicines. Branches were used to make the altar for the Sun Dance [60]. The Navajo made red dye from the roots [38].
Honeybees are American plum's principal pollinator (review by [46]). As of 2010, information on American plum's native pollinators was not available.
American plum does not effectively cross-pollinate with agricultural Prunus species [44].
Information on conditions favoring American plum seedling establishment was not available as of 2010. Since American plum is most common on moist sites (see Site Characteristics), moist soil during early development is likely crucial.
American plum's growth rate is "moderate" [148,175] to "rapid' [167]. On coal mine spoils in Wyoming, unirrigated American plum transplants grew an average of 1.8 inches (4.5 cm)/year over 4 years [15]. In a common garden experiment in Nebraska, relative growth rates of American plum seedlings were 48% faster in sun than in shade [120].
There is much more information on American plum succession in the Great Plains than elsewhere. Further studies are needed on successional trends of American plum in its eastern and southern distributions. American plum is generally most successful on sunny, moist sites in early succession.
Light tolerance: American plum tolerates some shade but prefers full sun on sites with sufficient soil moisture. It is reported on open to wooded sites across its range [69,182]. It grows in "thin" woods in the Southeast [33]. In southeastern Michigan, it occurs in the most open, driest black oak woodlands [6]. It grows on open prairies (review by [46]) and prairie edges in mesic to moist areas. Ewing [39] identified American plum as one of the thicket-forming shrubs that form on shrubland-prairie ecotones of northwestern Minnesota.
Seral status: American plum is most common in early [87,196] to late-middle [101] succession. It is apparently rare in old-growth forests [153].
Disturbance generally favors American plum. It is common in disturbed areas such as roadsides, fencerows [33,52,53,112,182], pastures, and old fields [33]. American plum formed thickets alongside an old wagon trail in pristine big bluestem prairie in Kansas [71]. Bird-dispersed American plum seed often establishes in old fields and abandoned orchards [10]. American plum seedlings first occurred on Michigan old fields 7 years after abandonment [45]. American plum colonizes stream- and riverbanks (review by [152]), but it is generally not a floodplain colonizer [86].
Woodland and forest succession: Disturbances that favor grasses over shrubs can result in American plum decline. In white oak-black oak woodlands of the Morton Arboretum, Illinois, cattle grazing resulted in decline of the white ash overstory and the tall shrub understory, which included American plum, with attendant increases in nonnative grasses. White ash recruitment in the grass layer was poor [101,102]. See Fire Effects and Management for information on fire's role in maintaining American plum and other fire-tolerant shrubs.
American plum often persists in woodlands unless the woodland succeeds to forest. It is typically a shrub-layer component in woodlands (see Habitat Types and Plant Communities) but grows into the tree layer occasionally [155]. In green ash draws of North Dakota, American plum was about equally important in the seedling and shrub layers, ranging from about 1% to 20% cover. It did not gain access to the canopy layer [51]. American plum may persist or codominate with chokecherry, Saskatoon serviceberry, or other shrubs in nonforested woody draws in late succession in the Dakotas [150].
American plum declines with canopy closure, so it is uncommon in late succession. It is reported as occasional in late-successional northern red oak (Quercus rubra)-bitternut hickory forests with well-developed understories in Coon Valley, Wisconsin [113] and as rare in second- and old-growth white oak/flowering dogwood (Cornus florida) forests of the Missouri Ozarks [153]. In Nebraska, American plum and other understory shrubs are often suppressed in mature bur oak-bitternut hickory forests, gaining height only at forest-shrubland ecotones and in shrubby patches [184].
American plum is generally a late-seral species in riparian zones. It is often common in the elm-ash-cottonwood ecosystem, typically reported in seral elm-ash communities. However, it is rare in early-seral, floodplain cottonwood or closed-canopy elm communities (see Habitat Types and Communities). It is rare in the understories of cottonwood [141] and ash gallery forests, which develop along rivers in late successional stages (review by [84]). In ash-dominated galleries, ash generally becomes dominant in the last stages of floodplain succession, following cottonwoods and willows successionally. American plum is a component of some late-seral green ash gallery forests in the Central Great Plains (review by [84]). It also persists into late seral stages in some ash-dominated draws. On scoria buttes of western North Dakota, American plum was described as a dominant species—probably in the understory—of "postclimax" green ash-bur oak communities that formed along streambeds [80].
Grassland succession: Although American plum occurs in mesic, wooded draws in the Great Plains [4], it may be unlikely to colonize prairies where fire or other stand-replacing disturbances are excluded. In Pipestone National Monument, Minnesota, American plum occurred in small patches within a big bluestem-prairie sandreed prairie but was not among the woody species considered prairie invaders [9]. On the Konza Prairie Biological Station, a 15-year study on type conversion of tallgrass prairie to shrub-grass savanna found American plum was too infrequent for statistical analyses. Some study sites had been burned under prescription. The most successful woody invaders on both unburned and burned sites were honeylocust (Gleditsia triacanthos) and American elm; roughleaf dogwood (Cornus drummondii) was also invasive on infrequently burned sites [19]. In extensive studies in Nebraska, Weaver [184] did not find American plum spreading onto prairies as an early colonizer. In eastern Nebraska, smooth sumac first invaded little bluestem-blue grama mixed-grass prairie, followed by western snowberry (Symphoricarpos occidentalis). Although American plum was the 3rd most common member of the smooth sumac-western snowberry community, it was not reported as a grassland colonizer. The smooth sumac-western snowberry shrubland is replaced successionally by bur oak-bitternut hickory forest. In the forest community, American plum's successional status regressed from a subdominant species to an associated species. Shrubs in general were less important in the forest stage [4].
American plum's physiology and morphology (shallow roots) may prevent it from becoming an early-seral grassland invader. Studies on the Konza Prairie suggest that on prairie sites, American plum's photosynthetic gains are less than those of roughleaf dogwood, an invasive shrub, and big bluestem, the dominant grass [117]. American plum apparently competes poorly with bluestems (Andropogonacea) and smooth sumac—another invasive shrub that is invading prairies with fire exclusion—for water. On unburned sites on the Konza Prairie Biological Station, growing-season water-use efficiency and photosynthetic rates of 3 Great Plains shrubs (American plum, roughleaf dogwood, and smooth sumac) were compared to rates of little bluestem. Smooth sumac—the prairie colonizer—had water-use efficiency and photosynthetic rates closest to that of the drought-tolerant little bluestem, while American plum was not as efficient as either little bluestem or smooth sumac at either extracting soil water or at maintaining a high rate of photosynthesis throughout the growing season (P<0.05). The authors concluded that on prairies where fire is excluded, American plum is not as likely to invade as more water-use efficient shrubs such as smooth sumac and roughleaf dogwood [117]. However, American plum may establish in late-successional wooded areas within prairies where fire or stand-replacing disturbances are excluded [118,143,144]. See FIRE REGIMES for more information.
Limited evidence suggests that American plum may grow on open grasslands where there is sufficient soil moisture. American plum is unlikely to persist if the grassland succeeds to forest. In a chronosequence study of old fields in oak-pine ecosystems on the Piedmont of Georgia, American plum and other shrubs cooccurred with broomsedge bluestem (Andropogon virginicus) and other Andropogon in early succession, about 3 years after field abandonment. Loblolly pine (Pinus taeda) and shortleaf pine (P. echinata) formed a closed canopy as early as 15 to 20 years after abandonment. On a 15-year-old field, American plum grew among broomsedge bluestem and other grasses, reaching 10 feet (3 m) in height. In a 25-year-old forest, American plum was a component of thickets that formed in grassy areas. It was not noted as a component of 60-year-old or older forests. One-hundred-year-old forests were dominated by shortleaf pines, and a deciduous understory had developed. After 150 to 200 years, forests had succeeded to white oak-black oak-hickory (Carya spp.) forests with an understory of dogwoods, hawthorns, and other small trees. American plum was not reported as a component of these old-growth forests [77].
Grazing: American plum may decline with sustained heavy grazing. See Other Management Considerations for details.The scientific name of American plum is Prunus americana Marsh. (Rosaceae)
[53,68,82,90,106,112,137,182,187,193].
American plum is most closely related to [99] and hybridizes naturally with Chickasaw plum (P. angustifolia Marsh.), producing P. × orthopsepala Koehne [82,106]. Many horticultural crosses have been made with American plum and other Prunus [36,44,75].
American plum is used for restoration plantings ([18,81], reviews by [42,152]), wildlife habitat and food plantings [13,36,48,81,111,151], windbreaks ([48,48,81,111,140], review by [152]), shelterbelts ([76,148], review by [152]), snow fences [151], mine spoil restoration [13,15,128], and erosion control. Since it forms thickets, it is highly useful for erosion control ([21,81], reviews by [46,152]). Plant materials are available commercially [123]. See these sources: ([79,81,134,160,167,169], review by [46]) for information on propagating and outplanting American plum.
Outplanting results: American plum is recommended for plantings on shallow to deep, moist to mesic soils in the Central Great Plains [140]; it is likely to perform well in the Northern Great Plains but fail to thrive in the Southern Great Plains and Southwest. American plum transplants used in highway plantings in Wisconsin averaged 93% survivorship after 5 years. They were watered during their first 2 years, which were droughty [59]. Two years after plantings in decadent, poorly regenerating green ash-American elm draws on the Little Missouri National Grassland, North Dakota, American plum transplants had 65% survival with cattle grazing and 89% survival without [14,18]. On coal mine spoils of Wyoming, American plum container and bareroot stock showed good survivorship (60% and 87%, respectively) with irrigation. Without irrigation, container stock showed poor survivorship (27%) compared to other container-grown species, while bareroot stock survivorship was about average (40%) compared to other bareroot-planted species [15]. For big game and other restoration projects in Utah, American plum was rated as showing poor initial establishment and growth but good persistence and spread in pinyon-juniper, big sagebrush, blackbrush (Coleogyne ramosissima), and mountain brush communities [133,134]. American plums transplanted on a strip-mined site in eastern Texas had 100% mortality 3 to 8 years after planting. Overall survivorship of shrubs was low on the site [54], and American plum was outside its native distribution.
On wildlife habitat planting sites in New York, Vermont, and Pennsylvania, hybrids of American plum and sand cherry (P. besseyi) showed poorer survival than sand cherry, so the authors recommend against using the hybrids for planting. American plums were not planted [36].
Prunus americana, commonly called the American plum,[6] wild plum, or Marshall's large yellow sweet plum, is a species of Prunus native to North America from Saskatchewan and Idaho south to New Mexico and east to Québec, Maine and Florida.[7]
Prunus americana has often been planted outside its native range and sometimes escapes cultivation.[8] It is commonly confused with the Canada plum (Prunus nigra), although the fruit is smaller and rounder and bright red as opposed to yellow. Many cultivated varieties have been derived from this species. It forms an excellent stock upon which to graft the domestic plum.[9]
The American plum grows as a large shrub or small tree, reaching up to 4.6 metres (15 feet).[10] It is adapted to coarse- and medium-textured soils, but not to fine soils (silt or clay). Beneficially, the shrub survives harsh winters, down to temperatures of -40 degrees (Fahrenheit);[11] but has little tolerance for shade, drought, or fire. Its growth is most active in spring and summer; it blooms in spring and starts fruiting in summer. It propagates naturally by seed, expanding as a stand relatively slowly, due to its long time to maturity when grown from seed.[12][13]
The roots are shallow, widely spread, and send up suckers.[10] The numerous stems per plant become scaly with age. The tree has a crown width and height of 10 feet at maturity.[14] The branches are thorny. The leaves are alternately arranged, with an oval shape. The leaf length is usually 5.1–10.2 centimetres (2–4 inches) long. The upper surface of the leaf is dark green; the underside is smooth and pale. The small white flowers with five petals occur singly or in clusters in the leaf axils. The globular fruits are about 2.5 cm (1 in) in diameter.[12]
Prunus americana var. lanata Sudw is considered a synonym of Prunus mexicana, and Prunus americana var. nigra is considered a synonym of Prunus nigra.[6]
Chickasaw plum (Prunus angustifolia Marsh.) hybridizes naturally with P. americana to produce P. × orthosepala Koehne.[15]
In cultivation, many crosses have been made between American plum and other Prunus species, including Prunus persica, the peach.
The American plum is used for both ornamental and culinary purposes. The white flowers are decorative in spring and its short, single leader makes it a popular residential landscape tree. Sargent says of it: "As an ornamental plant P. americana has real value; the long wand-like branches form a wide, graceful head which is handsome in winter and in spring is covered with masses of pure white flowers followed by ample bright foliage and abundant showy fruit."[9] More than 200 forms of American plum have been grown for cultivation. The sour and sweet fruit is eaten fresh and is processed as preserves, jellies, jam and wine.[8]
Farms use medium to tall shrubs or trees for windbreaks, and highway or riverside plantings. Its high density of growth effectively reduces the wind velocity near the ground. Development of suckers from the root system makes American plum effective in stabilizing stream banks and gullies. It will tolerate several days of flooding. Some commercial properties plant the trees along the entrance road.[16]
Many birds and animals eat the fruit, and both white-tailed deer and mule deer feed on twigs and leaves.[17][18]
Traditionally, American plum was extensively used by Native Americans. Eastern Native Americans planted many trees giving many places the name of Crab Orchard.[19]
The Plains Indians and Cheyenne ate the plums;[20] the latter used the branches for the Sun Dance. The Navajo used the roots to make a red dye.[21][22]
American plums are described in Laura Ingalls Wilder's On the Banks of Plum Creek (1937):
You must know exactly how to shake a plum tree. If you shake it too hard, the green plums fall, and that wastes them. If you shake it too softly, you do not get all the ripe plums. In the night they will fall, and some will smash and be wasted.
Laura learned exactly how to shake a plum tree. She held its scaling-rough bole and shook it, one quick, gentle shake. Every plum swung on its stem and all around her they fell pattering. Then one more jerk while the plums were swinging, and the last ripe ones fell plum-plump! plum-plump! plump! plump!
There were many kinds of plums. When the red ones were all picked, the yellow ones were ripe. Then the blue ones. The largest of all were the very last. They were the frost plums, that would not ripen until after frost.[23]
{{cite web}}: CS1 maint: others (link) Note that this website has been superseded by World Flora Online Prunus americana, commonly called the American plum, wild plum, or Marshall's large yellow sweet plum, is a species of Prunus native to North America from Saskatchewan and Idaho south to New Mexico and east to Québec, Maine and Florida.
Prunus americana has often been planted outside its native range and sometimes escapes cultivation. It is commonly confused with the Canada plum (Prunus nigra), although the fruit is smaller and rounder and bright red as opposed to yellow. Many cultivated varieties have been derived from this species. It forms an excellent stock upon which to graft the domestic plum.
