Mountain Laurel

In Great Britain and/or Ireland:
Foodplant / pathogen
mycelium of Phytophthora ramorum infects and damages leaf of Kalmia latifolia

More info for the terms: fuel, fuel moisture, severity, shrubs

Fire effects to mountain laurel vary with season, severity, and intensity and
range from partial consumption to complete consumption of the aboveground plant.
Leaves of mountain laurel are reported to burn at high intensity; burning shrubs can
produce flame lengths of 100 feet (30 m) [120]. The combustible nature of mountain laurel
is suspected to be due to the oil or wax content of the leaves [74]. Also, fire behavior
characteristics are thought to be highly associated with live fuel moisture. In the southern
Appalachians, leaf moisture content of mountain laurel is highest (70%) in new growth and
declines as leaves mature. Live fuel moisture of leaves, twigs, and stems greater than
1-year-old average 50% to 60% moisture content (see:
Seasonal development) [84].

More info for the terms: cover, density, fire frequency, fire management, fire severity, fire use, forest, frequency, habitat type, hardwood, high-severity fire, low-severity fire, prescribed fire, restoration, severity, surface fire, tree, wildfire, xeric

The majority of research that has investigated mountain laurel fire effects is in the
context of silvicultural management for improvement of hardwood or pine forest yields.
In these forests, dense thickets of mountain laurel are commonly thought to be in
greater abundance than during the presettlement era. In addition, these thickets are
speculated to restrict regeneration of oak and other desirable hardwood species by
quickly outgrowing and limiting light resources in early-successional postharvest stands.
Thus, fire management in these forests centers around the use of prescribed fire to
reduce the abundance and competitive influence of mountain laurel. Typical treatments
involve the removal of merchantable timber and cutting and felling the remaining woody
stems and abandoning them as slash in the spring after leaf out. As the slash dries,
sprouts of less desirable species such as mountain laurel emerge and are burned during
the mid-summer. Much of the research focuses on the effects of varying fire intensities
and frequencies on postfire sprouting of mountain laurel [22,24,54,114,117].


Fire severity/intensity:
Mountain laurel responds to burning by sprouting abundantly after burning regardless of fire
intensity.


Two prescribed fires (one in 1984 and another in 1985) were used in combination with a
felling treatment in Connecticut to asses the postfire response of mountain laurel in a
70-to 80-year-old oak-hardwood stand. Burning was conducted in the spring. Each stand
endured both low- and high-severity fires which were measured as <30% or >70%
postfire reduction in tree stem density when compared to adjacent stands. After burning,
mountain laurel sprouted "quickly" and grew "vigorously" resulting
in heights higher than in adjacent unburned control stands 8 and 9 years after fire. The
most vigorous mountain laurel growth occurred in the severely burned area where overstory
mortality was greatest [85]. The following table represents average annual height growth
rates of mountain laurel in all treatments.


Severe Burn
Moderate Burn
Unburned Control

4.8 inches/year

3.9 inches/year
3.1 inches/year



A lightning caused wildfire in July 1988 at Virginia's Shenandoah National Park in
a Table Mountain-pitch pine forest revealed that mountain laurel sprouts quickly
after a variety of burn severities. Mountain laurel's sprouting response was stronger in the
more severe burn. Fire severity was assessed by measuring postfire cumulative tree mortality,
crown scorch, and stem char. The following table represents mountain laurel importance values 1 and 2 years postfire.


Postfire year High-severity Low-severity Unburned
+1 17.2 6.3 5.2
+2 14.5 6.0 3.7



Mountain laurel sprouted "rapidly" after spring burning in an
Appalachian Mountain oak forest with a mountain laurel dominated understory.
Increases in mountain laurel stems per hectare resulted after 2 separate fires each
representing low- to high-severity fire when compared to adjacent unburned
control stands. Low fire severity was characterized by the authors [31]
as a surface fire with limited torching of overstory trees, while severe fire
severity was characterized by extensive overstory torching and mortality. Low
fire severity resulted in higher densities of mountain laurel after 7 years
possibly because of mountain laurel's preference for shady sites. The following
table represents mountain laurel stems per hectare 7 years
postfire:



Control
Low-severity fire
Severe fire
Site 1
22,500
96,400
78,100
Site 2
35,700
90,200
76,100



Mountain laurel sprouted vigorously after an experimental restoration treatment
involving felling and burning at low severity in a southern Appalachian xeric
pine-hardwood forest. Thirteen years after burning, mountain laurel had established
21,525 stems per hectare [22]. Similar studies conducted by Clinton and Vose
[24] and Elliott and others [36] found comparable results.


Fire frequency:
The ability of mountain laurel to reproduce after repeated fire has been noted
in several studies.


In xeric pine-hardwood forests near the Red River Gorge in Kentucky, a prescribed
fire and a subsequent wildfire 2 years afterwards provided an opportunity to
study the effects of multiple burns on mountain laurel reproduction in 4 types of stands:
(1) adjacent unburned, (2) once burned (prescribed fire 1993), (3) once burned
(wildfire 1995), (4) and twice-burned (1993 and 1995). All burning occurred in the
spring. Sampling was conducted in August of 1997, 3 growing seasons after the wildfire
of 1995 and 5 years following the 1993 prescribed fire. Post-fire reproduction strategy
of new mountain laurel stems was unknown. After burning, new seedlings and/or sprouts
were most frequently observed growing underneath dead mountain laurel branches. Mountain laurel
increased in percent cover in all burns. The largest increase in percent cover of mountain laurel
was in the twice-burned plots [5]. Average percent cover of mountain laurel was as follows.

control 1993 burn 1995 burn 1993& 1995 burns
0.3 2.2 3.4 5.7


A fire history study in pine barren forests of New Jersey and New York analyzed
current vegetation patterns in relation to fire frequency. In this habitat type
mountain laurel is considered a strong sprouter that historically tolerated
short fire intervals (< 15 years) [132].

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

• Early postfire effects of a prescribed fire in the southern Appalachians of North Carolina
• Early postfire response of southern Appalachian Table Mountain-pitch pine stands to prescribed fires in North Carolina and Virginia
• Early postfire response of Table Mountain pine stands burned under prescription at varying intensities

mountain laurel



mountain-laurel



laurel

Location Rank
Maine Special Concern
Florida Threatened [113]
Vermont Uncommon [116]
New York Exploitably Vulnerable [113]



 

More info for the terms: burl, capsule, fruit, rootstock, sclerophyllous, shrub

This description provides characteristics that may be relevant to fire ecology,
and is not meant for identification. Keys for identification are available (e.g.
[12,21,40,42,62,94,108,134,135]).

Mountain laurel is a native North American perennial shrub [108]. Mature plants
are 6.5 to 10 feet (2-3 m) tall, but may reach up to 40 feet (12 m) in height.
Leaves are evergreen, sclerophyllous, leathery, 0.75 to 4 inches (2-10 cm) long,
and 1 to 2 inches (2.5-5 cm) wide [12,21,40]. The inflorescence is a compound corymb
of showy saucer shaped flowers, 0.5 to 1 inch (1.5-3 cm) wide. Stems are long and narrow
with furrows and ridges, often sloughing in narrow strips or flakes [62,134]. The
fruit is a capsule, 4-6 mm in diameter, bearing hundreds of small (< 1 mm in length,
< 0.5 mm wide) seeds [42,94,135]. Below a basal burl, mountain laurel has a thick
rootstock that supports numerous other vertical and horizontal roots that may reach up
to 30 inches (76 cm) in depth [70]. Mountain laurel roots associate with
mycorrhizal fungus [60,68].

Mountain laurel is common in the Appalachian Mountains, plateaus, piedmont, and
coastal plains from southeast Maine to the Florida panhandle, west to Louisiana,
and north through southern Indiana to southern Quebec [12,21,40,42,62,73,94,108,134,135]. Plants database provides a distributional
map of mountain laurel.

More info for the terms: codominant, density, fire frequency, fire management, fire regime, fire suppression, forest, frequency, fuel, litter, natural, serotinous, woodland, xeric

Fire adaptations:
Mountain laurel sprouts after burning from basal burls, rhizomes, or layered branches
[22,70,132]. Mountain laurel's reproductive success in habitats that have endured
frequent severe burning is speculated to be due to its ability to grow reproductive
rhizomes up to 30 inches (76 cm) into the soil, where they are insulated from the
heat of severe fires [70,132].


Fire regime:
:
Many scientists believe that before the colonization of eastern forests by European
settlers, forest fires were a major contributor to the stand dynamics of presettlement
forests. The ignition sources of these fires include Native Americans and lightning
[7]. Frequent burning is hypothesized as one of the most important elements of the
disturbance regime in some eastern forests, particularly in the xeric pine/hardwood
forest-types that are primarily composed of pine and oak species with an understory
of mountain laurel [123]. These stands are thought to be highly dependent on frequent,
high-intensity fires for their maintenance and rejuvenation. Mountain laurel presettlement
abundance may be a critical component of pine forest structure as a ladder fuel, allowing
fire to move from the surface to the crowns of serotinous pine species [112,120]. Fire
suppression practices of the 19th and 20th centuries have diminished aboriginal-and
lightning-ignited fires in these stands. In addition, drought-related insect infestations
and previous logging practices have led to decreased densities of pines and increased
densities of shade-tolerant overstory and understory species, including mountain laurel.
In these stands mountain laurel is thought to be a major reproductive competitor with
juvenile trees (See Successional Status),
so its removal from the understory in some
forests is currently a major objective of fire management
(See Fire Effects)
[36,86,112,117,124].


In oak forests with a mountain laurel dominated understory, infrequent (>25 years)
low-severity surface fires in leaf litter were once a common element of the presettlement
fire regime [110]. A few of these forests, especially in ecotonal areas with table mountain
and pitch pine, are believed to have endured infrequent stand replacement fires during
periods of severe fire weather conditions [22,115,124]. However, fire suppression efforts
have reduced the fire frequency in these forest types. The absence of fire in these
forests may be as the primary reason for the decrease in abundance of oak forests and
increase in abundance of mountain laurel and other shade-tolerant species over
the past century across the eastern U.S. [120].


In Tennessee's Great Smoky Mountains National Park, Harmon [49], using fire scar
data in a xeric pine-hardwood stand with a mountain laurel dominated understory,
found a mean fire frequency of 12.7 years and a fire rotation period of 10 to 40
years between 1856 and 1940. This period coincides with increased burning by
European settlers, decreased native American burning, and decreased burning from
natural ignitions due to fire suppression policies.


In pitch pine forests in New Jersey, fire intervals in stands where mountain laurel
is dominant or codominant vary from 5 to 60 years [132]. In these stands, increases
in the density of mountain laurel over the past century are speculated to be strongly
linked to the length of time between fires. Windisch [132] found that unburned stands
(>50 years) contain higher densities of mountain laurel than those that have recently
burned .


The following table provides fire return intervals for plant communities
and ecosystems where mountain laurel is important. 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".
Community or Ecosystem Dominant Species Fire Return Interval Range (years)
maple-beech-birch Acer-Fagus-Betula spp. >1,000
silver maple-American elm Acer saccharinum-Ulmus americana <5 to 200
sugar maple Acer saccharum >1,000
sugar maple-basswood Acer saccharum-Tilia americana >1,000
beech-sugar maple Fagus spp.-Acer saccharum >1,000
black ash Fraxinus nigra <35 to 200
yellow-poplar Liriodendron tulipifera <35 [119]
northeastern spruce-fir Picea-Abies spp. 35-200 [32]
southeastern spruce-fir Picea-Abies spp. 35 to >200 [119]
red spruce* Picea rubens 35-200 [32]
shortleaf pine Pinus echinata 2-15
shortleaf pine-oak Pinus echinata-Quercus spp. <10
longleaf pine-scrub oak Pinus palustris-Quercus spp. 6-10
Table Mountain pine Pinus pungens <35 to 200 [119]
red-white-jack pine* Pinus resinosa-P. strobus-P. banksiana 10-300 [32,51]
pitch pine Pinus rigida 6-25 [15,53]
pocosin Pinus serotina 3-8
eastern white pine Pinus strobus 35-200
eastern white pine-eastern hemlock Pinus strobus-Tsuga canadensis 35-200
eastern white pine-northern red oak-red maple Pinus strobus-Quercus rubra-Acer rubrum 35-200
loblolly-shortleaf pine Pinus taeda-P. echinata 10 to <35
Virginia pine Pinus virginiana 10 to <35
Virginia pine-oak Pinus virginiana-Quercus spp. 10 to <35
sycamore-sweetgum-American elm Platanus occidentalis-Liquidambar styraciflua-Ulmus americana <35 to 200 [119]
aspen-birch Populus tremuloides-Betula papyrifera 35-200 [32,119]
black cherry-sugar maple Prunus serotina-Acer saccharum >1,000 [119]
oak-hickory Quercus-Carya spp. <35
oak-juniper woodland (Southwest) Quercus-Juniperus spp. <35 to <200 [90]
northeastern oak-pine Quercus-Pinus spp. 10 to <35 [119]
oak-gum-cypress Quercus-Nyssa-spp.-Taxodium distichum 35 to >200 [87]
southeastern oak-pine Quercus-Pinus spp. <10
white oak-black oak-northern red oak Quercus alba-Q. velutina-Q. rubra <35
northern pin oak Quercus ellipsoidalis <35
bear oak Quercus ilicifolia <35
chestnut oak Quercus prinus 3-8
northern red oak Quercus rubra 10 to <35
post oak-blackjack oak Quercus stellata-Q. marilandica <10
black oak Quercus velutina <35
eastern hemlock-yellow birch Tsuga canadensis-Betula alleghaniensis >200 [119]
elm-ash-cottonwood Ulmus-Fraxinus-Populus spp. <35 to 200 [32,119]


*fire return interval varies widely; trends in variation are noted in the species review

More info for the terms: density, fuel, hardwood, layering, prescribed fire, tree

The primary objectives of felling and burning treatments are to reduce density of
mountain laurel and promote establishment of pine and hardwood overstory species. While
these treatments have shown success in improving the stocks of overstory tree species
[85], attempts at reducing mountain laurel abundance using fire have been unsuccessful.
Burning stimulates the growth of sprouts asexually by layering, suckering, or sprouting
from basal burls [22,31,45,87]. While some studies have shown initial sprouting of
mountain laurel after burning is somewhat sluggish until the 2nd growing season [22,36],
the abundance of mountain laurel after burning in mature postfire stands usually resembles
prefire abundance. Long term effects of using prescribed fire repeatedly require further
research.

Allometric equations for estimating dry biomass [9] have been used for predicting fuel
loadings of mountain laurel leaf, branch, and bole.

More info on this topic.

More info for the term: phanerophyte

RAUNKIAER [96] LIFE FORM:



Phanerophyte

More info for the terms: density, forest, mesic, tree, xeric

Soil:
Mountain laurel occurs commonly on xeric sites with rocky or sandy acidic soils on
southern-facing slopes, ridges, and mountain hillsides [8,40,75,81,94,108,134],
although it occasionally occurs on well-drained mesic floodplain soils
[135]. Mountain laurel may be less abundant or entirely absent on northerly-facing
mesic slopes or along stream bottoms [84]. Mountain laurel forms dense, almost impenetrable
patches known locally as "laurel hells" or "ivy thickets," on upper
slopes and ridges where tree canopy may be sparse or lacking [60,84]. These sites are
characterized by steep rocky slopes, high solar radiation, and acidic sandy soils
containing low amounts of organic matter [36,84,94,108,134]. In the southern Appalachian
Mountains mountain laurel occurs more frequently on sites with a thin A soil horizon
layer [82]. Where mountain laurel is common, soil nutrient levels and water availability
are generally low [64,82]. The following table shows average soil chemical and physical
properties from a southern Appalachian xeric oak-pine forest [64].


N (%) C (%) pH Ortho-p (mg kg-1) Ca (mg kg-1) K (mg kg-1) Mg (mg kg-1) Bulk density (g cm-3)
0.1 3.3 3.9 1.7 28 61 19 0.75



Mountain laurel foliage litterfall contributes nutrients back to forest soil [101].
The following table shows estimated average mountain laurel foliage
nutrient concentration percent.


Lignin (%)
Ca (%)
Mg (%)
P (%)
K (%)
21.5
1.58%
0.18%
0.01%
0.30%



Mountain laurel is dependent on mycorrhizal fungus associated with its root system
in the soil, which ensures adequate absorption of water and minerals even in areas of
nutrient-poor, acidic soil [60].


Climate:
Considerable climatic diversity is found throughout mountain laurel's range. In general,
temperature, precipitation, and length of growing season increase from north to south.
However, a wide variety of local microclimatic conditions exist in the complex topography
of the Appalachian Mountain region. Habitats that include mountain laurel endure climate
ranging from subtropical along coastal plains to temperate further inland. Seasonal weather
patterns are driven by alternating cold/dry continental air masses from Canada and warm/moist
air from the Gulf of Mexico. Precipitation is generally distributed uniformly throughout the
year mostly as rain, while snow and ice are common in the winter months, especially in
mountain laurel's northern range and higher mountainous terrain. Mean annual precipitation
ranges from 39 to 78 inches (1000-2000 mm). Depending on location, annual snow accumulations
range from 8 to 48 inches (200-1220 mm). Tropical cyclones are possible throughout the summer
and fall months and can result in very high amounts of precipitation and wind [20,44,103,105].


Annual average precipitation for select locations are:


State
Location
Mean Annual Precipitation
Citation
NC Coweeta 71.3 inches (1810 mm) [9]
KY Stanton 44.5 inches (1130 mm) [8]
TN Cleveland 53.2 inches (1350 mm) [55]



Seasonal variations in temperature increase away from the coast. Average winter
temperatures vary from 10 °F (-12 °C) in the north to 64 °F (18 °C) in mountain laurel's
southern range. Average summer temperatures are less variable, ranging from 70 to 72 °F
(21 to 22 °C) [20,44,103].

More info on this topic.

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

More info for the terms: cover, swamp

SAF COVER TYPES [37]:





1 Jack pine

5 Balsam fir

12 Black spruce

14 Northern pin oak

15 Red pine

17 Pin cherry

18 Paper birch

19 Gray birch-red maple

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

28 Black cherry-maple

30 Red spruce-yellow birch

31 Red spruce-sugar maple-beech

32 Red spruce

33 Red spruce-balsam fir

34 Red spruce-Fraser fir

35 Paper birch-red spruce-balsam fir

39 Black ash-American elm-red maple

40 Post oak-blackjack oak

42 Bur oak

43 Bear oak

44 Chestnut oak

45 Pitch pine

50 Black locust

51 White pine-chestnut oak

52 White oak-black oak-northern red oak

53 White oak

55 Northern red oak

57 Yellow-poplar

58 Yellow-poplar-eastern hemlock

59 Yellow-poplar-white oak-northern red oak

60 Beech-sugar maple

62 Silver maple-American elm

64 Sassafras-persimmon

65 Pin oak-sweetgum

70 Longleaf pine

71 Longleaf pine-scrub oak

74 Cabbage palmetto

75 Shortleaf pine

76 Shortleaf pine-oak

78 Virginia pine-oak

79 Virginia pine

80 Loblolly pine-shortleaf pine

81 Loblolly pine

82 Loblolly pine-hardwood

83 Longleaf pine-slash pine

84 Slash pine

85 Slash pine-hardwood

87 Sweetgum-yellow-poplar

88 Willow oak-water oak-diamondleaf (laurel) oak

89 Live oak

91 Swamp chestnut oak-cherrybark oak

92 Sweetgum-willow oak

93 Sugarberry-American elm-green ash

94 Sycamore-sweetgum-American elm

96 Overcup oak-water hickory

107 White spruce

108 Red maple

109 Hawthorn

110 Black oak

More info on this topic.

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):

ECOSYSTEMS [39]:





FRES10 White-red-jack pine

FRES11 Spruce-fir

FRES12 Longleaf-slash pine

FRES13 Loblolly-shortleaf pine

FRES14 Oak-pine

FRES15 Oak-hickory

FRES18 Maple-beech-birch

More info on this topic.

This species is known to occur in association with the following Rangeland Cover Types (as classified by the Society for Range Management, SRM):

More info for the terms: cover, hardwood

SRM (RANGELAND) COVER TYPES [102]:




421 Chokecherry-serviceberry-rose

809 Mixed hardwood and pine

810 Longleaf pine-turkey oak hills

812 North Florida flatwoods

Fire top-kills mountain laurel [120,132].

More info for the term: cover

Mountain laurel's
leaves, buds, flowers and fruits are poisonous and may be lethal to livestock
and humans [4,77]. However, white-tailed deer,
eastern cotton tails, black bear, and ruffed grouse are known to
utilize this species especially as winter forage or during years of food
shortages [30,48,60,61,69,109,110,118].



Palatability/nutritional value:

Nutritional values of mountain laurel foliage were analyzed 10 to 12 months after spring
burning and in adjacent unburned stands in northeastern Georgia. The
authors [109] believed that their methodology underestimated crude fat
values. Percent composition of mountain laurel foliage before and after
burning follows:

  Unburned Burned
Moisture 52.5 56.5
Crude protein 8.2 9.9
Crude fat 2.5 1.9
Crude fiber 14.7 13.7
Nitrogen (free extract) 71.0 70.9
Ash 3.6 3.6
Calcium 0.87 0.79
Phosphorus 0.116 0.139




Cover value: Animals that associate with mountain laurel include white-tailed
deer, eastern screech owl, black bear, ruffed grouse, and various song
bird species [104,109,110]. Black
bears are known to den in "ground nests" in
mountain laurel thickets [122].

More info for the terms: codominant, fern, fire suppression, forest, hardwood, heath, herbaceous, lichens, marsh, mesic, shrub, shrubland, shrubs, tree, vines, xeric

Mountain laurel occurs in the understory of a variety of habitat types and plant
communities throughout eastern North American. It may be found within many plant
associations of the southern and Mid-Atlantic states. While not intended
as an exhaustive or definitive list, the following are specific examples of
communities in which mountain laurel can be found.

Mountain laurel is found in openings or open stands of spruce-fir (Picea-Abies
spp.) forests in the central and southern Appalachian arboreal highlands, mountain
tops, and "balds" (see below) [16]. These types of forest are dominated by red
spruce (P. rubens) but may coalesce with mixed hardwood or northern hardwood
forests on lower slopes. Common overstory associates include Fraser fir (A. fraseri),
yellow buckeye (Aesculus flava), sweet birch (Betula lenta), and black cherry
(Prunus serotina) [38,41]. Common understory associates include rhododendrons
(Rhododendron spp), American mountain-ash (Sorbus americana), and possumhaw
(Viburnum nudum var. cassinoides) [2,66,111]. Other understory associates
include highbush cranberry (V. edule), mountain holly (Ilex montana), speckled
alder (Alnus rugosa), pin cherry (P. pensylvanica), serviceberry (Amelanchier spp.),
raspberries (Rubus spp.), blueberries (Vaccinium spp.), and huckleberries
(Gaylussacia spp.) [100,128]. In closed red spruce stands, mosses, lichens, and
clubmosses (Lycopodium spp.) dominate the understory along with other shade tolerant
species such as wood sorrel (Oxalis spp.), trillium (Trillium spp.), and
wintergreen (Gaultheria procumbens) [127].

Heath "balds" that form along the tops of the highest (>4000 feet
(1200 m)) southern and central Appalachian mountain peaks are dominated by dense thickets
of ericaceous shrubs. Mountain laurel is a dominate species of these habitats or may
co-dominate with Catawba rosebay (Rhododendron catawbiense) at subxeric/submesic
ecotones [16,128]. However, a considerable difference in the distribution of these 2
species is present over an elevational gradient. Mountain laurel tends to favor the
lower elevation balds whereas above 6000 feet (1800 m), where the highest balds exist,
Catawba rosebay is common [4,5,9,17]. Common shrub associates include Catawba rosebay,
black chokeberry (Photinia melanocarpa), mountain sweetpepperbush (Clethra acuminata),
highbush blueberry (Vaccinium corymbosum), mountain holly, possumhaw, blackberries,
and American mountain-ash. Herbaceous abundance is limited by these dense thickets [44,100,127].

Mountain laurel is a common understory component of northern hardwood forests.
These forests are generally found at middle to high elevations in the central and
northern Appalachian Mountains, often transitioning to spruce/fir or mixed
hardwood forest at higher or lower elevations, respectively [103,111,128]. Common
overstory tree species include sugar maple (Acer saccharum), basswood
(Tilia americana), yellow birch (B. alleghaniensis), black cherry,
red spruce, white spruce (Picea glauca), American beech (Fagus grandifolia),
eastern white pine (Pinus strobus), eastern hemlock (Tsuga canadensis),
northern red oak (Quercus rubra), white oak (Q. alba), and yellow-poplar
(Liriodendron tulipifera) [100,103]. Understory associates include beaked hazel
(Corylus cornuta), eastern leatherwood (Dirca palustris), red elderberry
(Sambucus racemosa var. racemosa), alternate-leaf dogwood (Cornus alternifolia),
bush-honeysuckle (Diervilla lonicera), Canada yew (Taxus canadensis),
red raspberry (Rubus idaeus), and blackberries. Carolina springbeauty
(Claytonia caroliniana), snow trillium (Trillium grandiflorum), anemone
(Anemone spp.) marsh blue violet (Viola cucullata), downy yellow violet
(V. pubescens), hairy Solomon's seal (Polygonatum pubescens), starry
Solomon's-seal (Maianthemum stellatum), hairy sweet-cicely
(Osmorhiza claytonii), adderstongue (Ophioglossum spp.), Jack-in-the pulpit
(Arisaema triphyllum), bigleaf aster (Eurybia macrophylla), and
clubmosses [103,127].

Mountain laurel is an understory species associated with mixed hardwood forest. This
habitat occurs on rich, mesic sites, on sandy plains, rock outcrops, and at the outer edges
of floodplains east of the Mississippi. These forests often support a high level of plant
diversity [89,107,111]. Overstory associates of mountain laurel are numerous and include northern
red oak, white oak, black oak (Q. velutina), scarlet oak (Q. coccinea), southern
red oak (Q. falcata), post oak (Q. stellata), yellow-poplar, eastern white pine,
American beech, sugar maple, red maple (Acer rubrum), black cherry, American basswood,
sweetgum (Liquidambar styraciflua), white ash (Fraxinus americana), green ash
(F. pennsylvanica), aspen (Populus tremuloides), hickories (Carya spp.),
black tupelo (Nyssa sylvatica), black walnut (Juglans nigra), jack pine (Pinus
banksiana), eastern hemlock [56], and elm (Ulmus spp.) [12,79,128]. Common mid-canopy
tree associates include flowering dogwood (Cornus florida), holly (Ilex spp.),
eastern hophornbeam (Ostrya virginiana), sassafras (Sassafras albidum), American
bladdernut (Staphylea trifolia), eastern redbud (Cercis canadensis), common persimmon
(Diospyros virginiana), and serviceberry. Common understory shrubs and vines include
greenbrier (Smilax spp.), blueberries, rosebay rhododendron (Rhododendron maximum),
eastern leatherwood, witch-hazel (Hamamelis virginiana), beaked hazel, spicebush
(Lindera benzoin), poison-ivy (Toxicodendron radicans), and grape (Vitis spp.)
[6,100].

Mountain laurel is the primary understory species of xeric pine (Pinus spp.)
-hardwood forest. This forest type is common on southerly facing
slopes in the southern and central Appalachians, adjacent foothills, piedmont,
and coastal plains. These forests are thought to be highly dependent on moderate- to
high-intensity fires [112]. However fire suppression, drought-induced insect infestations,
and logging have promoted the dominance of hardwood species and dense thickets of mountain laurel
in later-successional stands [110,111]. Early-successional stands are dominated by pitch pine
(P. rigida), Table Mountain pine (P. pungens), and/or Virginia pine
(P. virginiana) [10,29]. As stands mature, other associated tree species
arrive [86] and include chestnut oak (Q. prinus) [27,28], white oak, bear oak
(Q. ilicifolia), blackjack oak (Q. marilandica), chinkapin oak
(Q. muehlenbergii), post oak, black oak, shortleaf pine (P. echinata),
scarlet oak, red maple, black tupelo, sourwood (Oxydendrum arboreum), American chestnut
(Castanea dentata), black locust (Robinia pseudoacacia), hickories, and
sassafras [14,86,93,107]. Associated shrub species include downy serviceberry (Amelanchier arborea),
coastal sweetpepperbush (Clethra alnifolia), black huckleberry (G. baccata), dwarf
huckleberry (G. dumosa), blue huckleberry (G. frondosa), sheep-laurel
(Kalmia angustifolia), wintergreen, fetterbush (Leucothoe racemosa), maleberry
(Lyonia ligustrina), piedmont staggerbush (L. mariana), bayberry (Morella spp.),
black chokecherry, black cherry, flameleaf sumac (Rhus copallinum), cat greenbrier
(Smilax glauca), roundleaf greenbrier (S. rotundifolia), Virginia tephrosia
(Tephrosia virginiana), low sweet blueberry (Vaccinium angustifolium), and hillside
blueberry (V. pallidum)
[5,17,57,130].

Mountain laurel is a common understory species of oak (Quercus spp.)-hickory
forests in the southern and east-central United States. Oak-hickory forests
are found on sand deposits and on dry upper slopes, ravines, and ridges of
southerly or westerly aspects [100]. This type of forest covers approximately 127
million acres (51 million ha) or 34% of the forests in the eastern U.S. Oak-hickory
forest dominates the east-central U.S. but gives way to mixed hardwoods to the north
and in the higher terrain of the Appalachian Mountains, and to pine-hardwood forest to
the south [110]. Dominant overstory associates include blackjack oak, post oak, northern
red oak, white oak, black oak, scarlet oak, southern red oak, and turkey oak (Q. laevis).
Other overstory associates include pignut hickory (C. glabra), black hickory, mockernut
hickory (C. tomentosa), shingle oak (Q. imbricaria), winged elm
(U. alata), black tupelo, and sourwood [12,111,128]. Understory tree and shrub
associates include flowering dogwood, blueberries, huckleberries, and sumac (Rhus spp.).
Herbaceous plant associates include bluestems (Andropogon spp.), little bluestem
(Schizachyrium scoparium), and various sedges (Carex spp.) [14,100].

Mountain laurel is an understory associate of eastern white pine forests.
These forests occur on a variety of sites along a moisture gradient from wet bogs
and moist stream bottoms to xeric sand plains and rocky ridges. Eastern white pine
often forms pure stands but more frequently occurs as a codominant or associate of
northern hardwood or mixed hardwood forest types containing northern red oak and/or
red maple [111]. In the northern range of this species through Maine and New Brunswick,
eastern white pine forests occur on mesic sites along or near bogs. In the southern and
central Appalachian Mountains, pure stands mainly occur on northerly aspects, in coves,
and on stream bottoms [100]. Due to the large amount of shade in the understory of
these forests, herbaceous and shrub species are scarce in pure stands of eastern
white pine. On dry sites where stand densities may allow more light, mountain laurel's
understory associates include blueberry, wintergreen, bush-honeysuckle, sweet fern
(Comptonia peregrina), western bracken fern (Pteridium aquilinum),
clubmoss, and broomsedge bluestem (A. virginicus) [6,26]. On moist rich sites,
associates include mountain woodsorrel (Oxalis montana), partridgeberry (Mitchella
repens), wild sarsaparilla (Aralia nudicaulis), Jack-in-the-pulpit, and
eastern hayscented fern (Dennstaedtia punctilobula). Herbaceous
associates include bigleaf aster, wild lily-of-the-valley (Maianthemum
canadense), and bunchberry (Cornus canadensis) [103,125].

Mountain laurel commonly occurs in the understory of oak-pine forest.
These forests are found along the Atlantic and Gulf coastal plains, piedmont,
and floodplains. Pines may make up 25% to 50% of the composition of these
forests [126]. Common overstory associates include shortleaf pine, loblolly pine
(P. taeda), scarlet oak, southern red oak, water oak (Q. nigra),
willow oak (Q. phellos), black tupelo, sweetgum, Table Mountain pine, mockernut
and pignut hickories, winged elm, sourwood, red maple, American beech, and Carolina ash (F.
caroliniana). Common understory woody species include flowering dogwood, redbud, and
common persimmon [20,91,100,110,111].

Mountain laurel frequently occurs in "pine barren or plain"
communities of the New Jersey and New York coastal plains [132]. These habitats
have a limited distribution of fire-dependent habitats ranging from pine forests to
dwarfed (< 10 feet (3.0 m) tall) shrubland communities [88]. Dominant overstory
species include pitch pine and other tree species such as blackjack oak, bear oak,
shortleaf pine, and dwarf chinquapin oak (Q. prinoides). Shrub associates
include black huckleberry, hillside blueberry, dangleberry (Gaylussacia frondosa),
piedmont staggerbush, and highbush blueberry  [20,43,57,78,129].

Mountain laurel is an occasional understory species in upland and mesic sites within
longleaf pine (P. palustris) forests and savannas. The fire
dependent forests dominated by longleaf pine are located in and along the
Atlantic and Gulf coastal plains and lower Piedmont regions of Georgia
and Alabama [91]. Associated species on mesic coastal plain sites include southern
red oak, blackjack oak, water oak, flowering dogwood, black tupelo, sweetgum, persimmon,
and sassafras. Associated species on xeric sandhill sites include turkey oak, bluejack oak
(Q. incana), and live oak (Q. virginiana). Associated shrubs include inkberry
(I. glabra), yaupon (I. vomitoria), large gallberry (I. coriacea),
southern bayberry (Myrica cerifera), blueberries, huckleberries, blackberries,
saw-palmetto (Serenoa repens), sweetbay (Magnolia virginiana), cyrilla
(Cyrilla racemiflora), and buckwheat tree (Cliftonia monophylla). In longleaf
pine's western range, groundcover includes bluestems and panicums (Panicum spp.).
In its eastern range, pineland threeawn (Aristida stricta) is the primary
groundcover [20,92,100].

Classifications describing plant communities in which mountain laurel is a
dominant species are as follows:

North Carolina [11,16,82,100]

South Carolina [1]

Tennessee [11,16,100]

West Virginia [46]

Virginia [16,46,100]

Blue Ridge Mountains [80]

More info for the terms: shrub, tree

Shrub



Shrub/Tree

More info for the term: fire management

See Fire Management Considerations.

Extracts from mountain laurel have been used to treat diarrhea,
upset stomach, skin irritations, and as a sedative [60].

Wood Products: Mountain laurel wood is heavy (green weight: 63 lbs/ft3), hard (1,790 lbf), and
strong, but rather brittle, with a close straight grain. Mountain laurel sapwood is yellow,
while the heart wood is yellow-brown with red spots [4]. The
wood of mountain laurel has a long history of uses by native and Euro-Americans.
It has been
used in the manufacturing of pipes, wreaths, roping, furniture, bowls,
utensils, and various other household goods and novelties. Economically,
mountain laurel
is the most important member of the genus Kalmia. The species is sold
commonly as an ornamental and the foliage is used in floral displays [4,60].

More info for the term: forest

KUCHLER [39]





K096 Northeastern spruce-fir forest

K097 Southeastern spruce-fir forest

K098 Northern floodplain forest

K099 Maple-basswood forest

K100 Oak-hickory forest

K101 Elm-ash forest

K102 Beech-maple forest

K103 Mixed mesophytic forest

K104 Appalachian oak forest

K106 Northern hardwoods

K107 Northern hardwoods-fir forest

K108 Northern hardwoods-spruce forest

K109 Transition between K104 and K106

K110 Northeastern oak-pine forest

K111 Oak-hickory-pine

K112 Southern mixed forest

K113 Southern floodplain forest

K114 Pocosin

More info on this topic.

More info for the terms: litter, seed

Mountain laurel stem growth occurs during the spring and ceases during summer.
Flowers bloom April to June from buds that form during the previous growing season.
Flowers are numerous and may number in the 1,000s, especially from individuals that
grow in open stands. Seed matures from September to October [94]. The majority of
mountain laurel leaves survive for 2 to 3 years. Mountain laurel leaves begin to
die in the late spring during their 2nd growing season while a few persist into the
3rd; hence, about half of the leaves on any given plant are the current year's
production. Leaf fall occurs throughout the year with peak litter production
occurring in the autumn and spring. Annual leaf litter production is 127 kg per
ha or 47% of its standing crop of leaves [84]. Mountain laurel leaf moisture content
peaks during late summer and is lowest during the spring [98].

More info for the terms: fire intensity, frequency, layering, severity

Mountain laurel sprouts from basal burls or by layering or suckering
"prolifically" regardless of fire intensity, severity, or frequency
[36,45,131,133].

More info for the terms: adventitious, geophyte, ground residual colonizer, initial off-site colonizer, rhizome, secondary colonizer, seed, shrub

POSTFIRE REGENERATION STRATEGY [106]:



Tall shrub, adventitious bud/root crown

Rhizomatous shrub, rhizome in soil

Geophyte, growing points deep in soil

Ground residual colonizer (on-site, initial community)

Initial off-site colonizer (off-site, initial community)

Secondary colonizer (on-site or off-site seed sources)

More info for the terms: basal area, burl, density, forest, layering, mesic, monoecious, seed, shrub, shrubs, stratification, tree, xeric

Mountain laurel regenerates from seed or asexually by sprouting, suckering, and layering [68,70,95,99,132].

Breeding system:
Mountain laurel is monoecious
[62]

Pollination:
is insect or self-mediated [62,118]. Bumblebees are the primary species of insect-mediated
pollination [95]. Mountain laurel anthers are positioned under tension which is suddenly
released when a bumblebee or other insect lands on the flower. If the flowers remain unpollinated,
the anther will self release pollen onto the flower's own pistil [12,68,71]. Real and Rathcke
[97] found that insect flower visitation depends on annual nectar production rates, which vary
from year to year.

Seed production:
Seeds are contained in small fruit-like capsules each containing 300 to 700
seeds. Individual mountain laurel shrubs can produce 1000s of seeds annually [68,95].

Seed dispersal:
Mountain laurel seeds are wind dispersed and rarely travel beyond 50 feet (15 m)
from the parent plant. Seedfall begins in the fall and continues through the spring
[68,95].

Seed banking:
Mountain laurel seed remains viable in the soil for several years [59,68]. Jaynes
[59] found that an average of 71% of seed 2 to 4 years old remained viable, whereas
viability declined to 20% after 8 years.

Germination:
Mountain laurel germination is enhanced by stratification [59,68]. Jaynes [59] found
that 66% of mountain laurel seed germinated after being refrigerated at 39 °F (4 °C) for
8 weeks versus 19% of untreated controls. Treatments using a gibberellin solution
also enhanced germination. Kurmes [68] found that germination of mountain laurel seed
is more successful when soil temperatures are 64 to 71.5 °F (18 to 22 °C).

Seedling establishment/growth:
Mountain laurel requires a moss-covered or moist mineral soil seedbed for successful
establishment [68,99]. Seedlings are moderately shade tolerant but tend to grow
more vigorously in forest openings [68,75]. Growth rates of mountain laurel are
relatively slow; young plants (< 15 years) add about 5 inches (12 cm) in height
and 3.5 inches (9 cm) in crown width annually [68,84]. Older mountain laurel stems
may attain heights up to 40 feet (12 m) and diameter at ground level of 5 inches (15 cm)
[60]. Mountain laurel is usually a tall, spreading shrub throughout most of its range,
yet in the fertile Blue Ridge valleys and in the Allegheny Mountains of the
southern Appalachian Mountains mountain laurel may attain the size of a small
tree. In 1877, botanist Asa Gray noted at Caesar's Head in extreme northwest South
Carolina that the trunks of mountain laurel reached 50 inches (125 cm) in circumference.
Mountain laurel burl size varies with age. A 600-pound (272 kg) burl has been reported
in western North Carolina [58]. In the southern Appalachian Mountains, mountain laurel stem
density can range from sparse to nil on mesic sites to thickets of over 26,000
stems/ha on xeric southerly slopes. Basal area of mountain laurel at 1 inch
(2.5 cm) above ground level can exceed 25 m2/ha [84].

Asexual regeneration:
Mountain laurel's primary mode of reproduction is through sprouting from basal burls,
layering, or suckering [68,70,99,132].

More info on this topic.

More info for the terms: basal area, cover, density, fire suppression, forest, hardwood, layering, litter, shrubs, succession, tree, xeric

Stand scale disturbances:
In the southern Appalachians and in other hardwood forests of the eastern U.S.,
mountain laurel quickly establishes after disturbance, sprouting aggressively from
basal burls [45]. Mountain laurel also re-establishes by suckering and layering
after disturbance. Mountain laurel is shade-tolerant and is typically found in the
understory of fast-growing, early-successional pioneer tree species such as
yellow-poplar, black locust, and red maple [33,94]. As postdisturbance stands
mature and senesce, mountain laurel commonly remains a dominant understory species
[47]. This is especially true in xeric communities such as pine-hardwood forest of the
southern Appalachians where mountain laurel often persists from early to late stages of
succession [18]. For example, Elliot and others [35] found mountain laurel stem
densities increased beyond precut densities during a 19-year period after a xeric
pine-hardwood forests was clear-cut. Years before and after cutting and percent
basal area of mountain laurel is as follows:


Pre-cut
Years after cutting
1974 +3 +5 +10 +19
18.8% 20.5% 37.% 34.7% 23.3%



Gap scale disturbances:
While large-scale canopy disturbances from regional drought, fire, and
ice storms do occur periodically, small-scale openings in the canopy are
much more common. These disturbances often come in the form of a
"canopy gap" created by the loss of 1 or more overstory individuals
by any number of factors (i.e. wind throw, lightning, disease, insect, etc.)
[83]. Canopy openings provide increased light and temperature to the forest
surface, stimulating establishment of new mountain laurel shrubs at a
disturbed site [23].


Synergistic relationships with overstory canopy:
In the southern Appalachians mountain laurel has grown abundant in areas where
insect outbreaks are responsible for mortality of overstory species. In xeric
pine-hardwood or oak-pine forests, drought-induced southern pine beetle attacks
are responsible for reducing densities of overstory tree species and increasing
densities of mountain laurel. In these stands successful regeneration of
overstory species is much less than in stands with less mountain laurel [22]. In
fact mountain laurel is hypothesized as the most important competitor to
regenerating hardwood and some pine species. Dense thickets of mountain laurel
form a barrier to juvenile trees, suppressing growth and limiting establishment
and survival. Mountain laurel's influence on overstory growth is lessened once
juvenile trees emerge from mountain laurel's canopy cover [22,34,63,85].



Some studies have found dissimilar results that indicate mountain laurel's
influence on overstory regeneration might be less than previously thought.
In northern hardwood and xeric pine-hardwood forests of New England, Kittredge
and Ashton [63] found that a dense understory of mountain laurel negatively
influenced only overstory pine species abundance, while overstory hardwood
species abundance remained uninhibited. In the southern Appalachians, Waterman
and others [121] found that the manual removal of mountain laurel from a
pine-hardwood stand did not influence recruitment and establishment rates of
juvenile trees. Clinton and others [23] found that the leaf surface area of
mountain laurel is less than that of other understory shrubs, allowing considerable
amounts of light to reach the forest floor for establishment of overstory
species beneath its canopy.


Increased abundance over the past century:
Increases in mountain laurel density across the Appalachian Mountains over the
past century may be due to loss of the once regionally dominant American
chestnut. This species was decimated by the chestnut blight of the early 20th
century. Canopy gaps provided by decadent chestnut overstory have allowed higher
amounts of light to reach the subcanopy and have contributed to increased abundance
of mountain laurel and other ericaceous shrubs over the past century [13,35]. Also,
the introduced gypsy moth has played a large role in shaping current forest structure
over the past century. Researchers in the central Appalachians using remote sensing
found that mountain laurel occurrence was strongly related to increased subcanopy
light caused by gypsy moth defoliation [19]. Other forest disturbances such as
logging and fire suppression have also contributed to the increase in mountain laurel
(see: Fire Regime)
[114].


Water and Light:
Mountain laurel is drought resistant and is a strong competitor for water resources
at xeric sites [25,72,84]. Mountain laurel adapts to a broad range of light regimes,
from moderate shade in forest understory to no shade in open or recently disturbed stands.
Al-Hamdani and others [3] found that mountain laurel foliage chlorophyll a:b ratio was
lower than that of other understory species. The authors considered this characteristic an
adaptation of mountain laurel to low light availability.


In the absence of disturbance:
Generally as juvenile stands mature, overstory canopy structure becomes more dense
and mountain laurel densities decline due to less light reaching the forest floor.
Hemond and others [52] found, in mixed hardwood forests of Connecticut, that mountain laurel
stem density declined 50% in maturing forests over a 20-year period. Harrod and others
[50] found similar declines of mountain laurel in maturing xeric pine-hardwood stands
in the southern Appalachians.


Nutrient flux: In southern Appalachian forests, mountain laurel has as a
large influence on nutrient flux in forest soils. Elliot and others [33] found
in soils where mountain laurel is abundant, the contribution of their low-nutrient
leaves to litterfall can reduce litter quality, alter pH, decrease forest floor
decomposition rates, and alter overall soil quality.

Kalmia latifolia L. var. laevipes Fernald [94]

The scientific name of mountain laurel is Kalmia latifolia L. (Ericaceae)
[12,21,40,42,62,94,108,134,135].

More info for the terms: forest, restoration

Mountain laurel is noted for preventing water runoff and soil erosion on
mountain hillsides. Researchers in the southern Appalachian Mountains found that excessive cutting of dense stands of
mountain laurel greatly increased the amount
of water runoff [60]. In urban and suburban parks and recreation areas
mountain laurel is commonly used in forest restoration projects that focus on stabilizing
thin soils [65].



 

Kalmia latifolia I.. Sp. PL 391. 1753
An irregularly branched shrub or small tree, with sparingly glandular-pubescent twigs and clammy-pubescent inflorescence; leaf -blades elliptic or oval, varying to broadest above or below the middle, mostly 5-8 cm. long, acute or slightly acuminate at both ends, dark-green above, pale-green beneath, with the midrib prominent beneath, manifestly petioled; clusters usually many-flowered; pedicels slender, villous, or merely puberulent in age, 1-3.5 cm. long; calvx 7-8 mm. wide, the lobes oblong, oblong-ovate, or lanceolate, usually glandular-ciliate,j acute; corolla pink or white, 2-2.5 cm. wide, sticky; filaments finely pubescent, at least to above the middle; ovary glandular; capsules spheroidal, 5-7 mm. wide, glandularviscid.
Type locality: Maryland.
Distribution: New Brunswick and Ontario to Florida and Louisiana.

Kalmia latifolia, the mountain laurel, calico-bush, or spoonwood, is a species of flowering plant in the heath family Ericaceae, that is native to the eastern United States. Its range stretches from southern Maine south to northern Florida, and west to Indiana and Louisiana. Mountain laurel is the state flower of Connecticut and Pennsylvania. It is the namesake of Laurel County in Kentucky, the city of Laurel, Mississippi, and the Laurel Highlands in southwestern Pennsylvania.