Authors: Carmen K. Converse, Global Invasive Species Team, The Nature Conservancy
Latin Name: Juniperus virginiana
Common Name: eastern cedar, red cedar
Eastern red cedar is an evergreen tree' native to eastern North America. Grown as an ornamental tree, and to a small extent for Christmas trees, it grows 5-20 m tall and up to 30 m in height. It has typically an ovoid or pyramidal crown. J. virginiana var. crebra Fern. and Grisc. has a more columnar shape (Fassett 1943). The red bark is thin (0.32 to 0.64 cm. thick) and exfoliates in long strips (Collingwood 1938). Leaves of seedlings and juvenile growth are acicular; adult plants have entire, opposite scale like leaves that are tightly appressed and overlapping. The scale like leaves have an oval dorsal gland. The species is dioecous (Van Haverbeke and Read 1976). The blue black, often glaucous fruit is a fleshy berry like cone. Each fruit usually contains one to two seeds (Van Haverbeke and Read 1976). For further description see Rosendahl 1970, Fernald 1950.
J. virginiana grows in the eastern United States and adjacent Canada from Ontario to South Dakota, Nebraska, Kansas, eastern Texas, to north Florida, and north to Nova Scotia (Van Haverbeke and Read 1976).
J. virginiana is very susceptible to fire destruction (Mohr 1901, Bray 1960, Arend 1950, Harper 1912, Collingwood 1938). It is a problem because it has rapidly invaded some grasslands and savannas mostly due to fire suppression (Beilmann and Brenner 1951, Arend 1950). In areas that once burned periodically, eastern red cedar was protected from fire on dry or rocky sites lacking sufficient herbaceous fuel to carry a fire (Martin and Crosby 1955, Arend 1950). As fire frequency decreased, eastern red cedar invaded adjacent, and apparently stable plant communities (Ormsbee et al. 1976). Subsequently, individual eastern red cedars have increased in size and coverage, and stand density has increased. Large trees and dense stands shade or otherwise inhibit growth of desired herbaceous vegetation (McBain 1983).
J. virginiana is most competitive on exposed dry sites. Plentiful habitat is provided by disturbed areas including abandoned pastures (Lutz 1928) and cultivated fields (Beilmann and Brenner 1951, Mohr 1901, Bard 1952, Ormsbee et al. 1976), eroded areas (Steyermark 1940, Quarterman 1950b) and open woods thinned by timber harvest. One result of this invasion is increased seed sources.
Rapid primary invasion and establishment may be followed by secondary invasion within six or seven years (Owensby et al. 1973). Rate of invasion and increases in stand density were examined on grazed pastures in Kansas. On heavily invaded pastures, Owensby et al. (1973 found a sigmoid population increase in nine years. In the nine years, cumulative numbers of plants on the heavily invaded pasture increased from about eight per acre (about 3/ha.) to about 180 per acre (about 73/ha).
Some natural habitats topographically and edaphically protected from fire include sandy loam covered bluffs; rocky hillsides (Wheeler 1900, Collingwood 1938); shale barrens of Virginia and W. Virginia; limestone glades of Tennessee, Virginia, Missouri and Arkansas (Erickson et al 1942); serpentine barrens of Pennsylvania and Maryland (Harper 1926); sandstone cliffs; granite outcrops; sand dunes; and estuarine swamps (Harper 1912).
It is adapted to a wide range of environmental conditions. Annual precipitation ranges from 40.64 cm. in the Great Plains to 152.40 cm. in the southeast United States. Temperature extremes range from 40° C to 46° C. Elevations range from 1524 m. to sea level (Van Haverbeke and Read 1976). Eastern red cedar thrives in well drained alluvial soils but also tolerates shallow limestone and sandstone soils and pH ranging from 4.7 to 7.8 (Arend 1950). It is able to grow where water is near the surface (Harper 1912) or where soil moisture fluctuates from near saturation in the winter to extreme dryness in the summer (Erickson et al. 1942). It is very drought tolerant (Pool 1939, Hinckley et al. 1979, Stiles and Melchers 1935). Exposure varies from north facing slopes of the plains (Albertson 1940), to south and west facing hillsides (Erickson et al. 1942) and near level glades (Quarterman 1950a) and coastal plains (Harper 1912). It is less vigorous in the shade of other trees, but can grow in the understory of deciduous species (Parker 1951) such as oaks and hickories of the Georgia Alabama coastal plain (Harper 1912, Mohr 1901) or cottonwoods of Great Plains riverbottoms (Van Haverbeke and Read 1976). It also may form pure stands (Mohr 1901).
J. virginiana is cultivated for shelterbelts and windbreaks, timber, ornamentals, cedar oil and associated uses (Van Haverbeke and Read 1976).
Eastern red cedar grows slowly and can live as long as 300 years (Collingwood 1938). Plant size and growth depend mostly on soil depth and moisture availability. On well drained alluvial and upland soils greater than 24 inches (60.96 cm.) in depth, average height is 45 feet (13.72 m.) after 50 years (Arend 1950). On soils less than twelve inches (30.48 cm.) deep, it rarely exceeds 20 (6.10 m.) to 30 feet (9.14 m.) in height (Arend 1950) and diameter growth is less than on deeper soils (Arend and Collins 1948). In the prairie region trees less than 20 feet (6.10 m.) tall may be 110 years old (Fowells 1965).
Growth activity is more related to moisture availability than other physiological or phenological reasons. Cambial activity increases when water is available.
On rangeland, Owensby et al. (1973) found that the ground level diameter of young red cedar increased 0.27 inches (.69 cm.) and height increased 7.85 inches (19.94 cm.) for each year of growth. The range of some plant heights was as follows: six year old 24 64 in. (0.60 m.-1.63 m.), seven year old 29 75 in. (0.74-1.91 m.), and ten year old 79 90 in. (2.01-2.29 m.) (Owensby et al. 1973). Those heights are of potentially sexually mature plants in the Great Plains, and have implications for fire management.
Eastern red cedar grows better than some other species in open areas having full sunlight, low soil moisture, and occasional drought. It is least competitive in shade. In a southern Illinois study, optimal photosynthetic rates occurred in full sunlight at temperatures between 20-25° C in the summer and 15-20° in the winter. Photosynthesis continued at low soil moistures and high temperatures, and at temperatures as low as 0° C (Ormsbee et al. 1976). The tightly packed branches especially of mature plants help to maintain warmer temperatures in internal foliage during the winter (Ormsbee et al. 1976) and reduce dessication to maximize winter photosynthesis. In grasslands herbaceous vegetation protects red cedar seedlings from winter cooling.
J. virginiana is more drought tolerant than associated deciduous woody species in open areas because it is able to rapidly produce taproots (Ormsbee et al. 1976) and has an extensive fibrous root system. It also conserves moisture by stomatal closure as an early drought response, and has finely dissected leaves providing cooling during stomatal closure (Hinckley et al. 1979).
In addition to eastern red cedar's evergreen growth and efficient and opportunistic moisture use, it also affects the soil and groundcover beneath its canopy. It shades desirable herbaceous species (McBain 1983, Gehring 1983), alters species composition (Gehring 1983) and raises surface soil pH (McBain 1983, Coile 1933, Spurr 1940). In Nebraska, Gehring (1983) found that groundcover of Poa pratensis L. and Carex spp. increased relative to increases in J. virginiana size. Coverage of prairie species beneath eastern red cedar decreased as tree size increased. McBain (1983) also found that tree canopy suppressed prairie species, and that soil moisture was reduced beneath trees.
Toxic substances produced in junipers may inhibit germination of some grass species. In tests of J. osteosperma (Torr.) Little, foliar extracts inhibited germination of Bouteloua gracilis HBK Lag. ex. Steud., B. curtipendula (Michx.) Torr and Agropyron desertorum (Fisch. ex. Link.) Schult. (Lavin et al 1968).
There is no natural asexual reproduction in red cedar. It does not resprout after complete cutting or burning (Arend 1950). Sexual maturity is reached in six (Owensby et al. 1973) to ten years (Van Haverbek and Read 1976). Staminate conelets have been observed on trees four to five years old, but similar information on ovulate conelet development is unavailable (Van Haverbeke and Read 1976). Staminate and ovulate conelets form on scale like foliage in September in North Carolina, but development is not complete until the next spring (Van Haverbeke and Read 1976).
J. virginiana exhibits variation in form, foliage color, vigor, height growth and disease resistance. Some of this variability results from hybridization with other junipers including J. ashei Buchholz in the Ozarks, J. scopulorum Sarg. in the Great Plains, J. silicicola (Small) Bailey in Florida, and J. horizontalis Moench. in the northern extent of red cedar's distribution (Van Haverbeke and Read 1976).
Pollen is wind dispersed from mid February to mid May depending on the location (Van Haverbeke and Read 1976). Fertilization is complete usually in June, and the embryo is mature in late July to mid November (Van Haverbeke and Read 1976).
Good seed crops are produced every two or three years with light crops in the intervening years. The best seed bearing age is between 25 and 75 years, although some trees will bear seeds at 10 years and some as late as 175 years (Fowells 1965). Seeds mature in autumn and are sometimes retained on the tree until the following spring (Phillip 1910).
Most seeds are dispersed by birds, including cedar waxwings, thrushes, starlings, robins, kingbirds, downy woodpeckers, and mockingbirds (Phillips 1910). Some seeds drop to the ground to germinate beneath mother trees, or are dispersed by small mammals (Parker 1951). Seedling density is greater near trees or along fencelines that provide perching sites, than in open sites (Phillips 1910, Martin and Crosby 1955). However, seedlings of other juniper species have been observed in open areas at long distances from these preferred perching sites (Burkhardt 1969).
"Most of the natural germination of eastern red cedar seed occurs in the early spring the second year after dispersal. A few seeds may germinate the first and third year. Delayed germination is caused by embryo dormancy and possibly by an impermeable seedcoat." (Folwells 1965)
There is considerable variation in stratification and scarification requirements probably due to the wide range and many genotypes of the species (Van Haverbeke and Read 1976). These requirements for propagation can be found in Seeds of Woody Plants in the United States (1974)
"On very dry sites most seedlings are found on protected places such as crevices or between layers of limestone where the microclimate is more favorable to germination (Albertson 1940)." (Fowells 1965)
Seedlings usually establish more readily on mineral soil than where a litter layer is present (Parker 1952, Lutz 1928), but are capable of establishment in thick sod (Lutz 1928, Steuter 1984). In pastures, a critical amount of mulch may influence establishment; too much or too little prevents germination (Owensby et al. 1973).
"Eastern red cedar seedlings withstand drought rather well because of their deep, penetrating taproot and relatively small leaf surface. During the first year seedlings do not produce much top growth, but they produce a long fibrous root system. Seedlings will often survive on arid sites, but their growth is slow.
The species is rather shade intolerant in the seedling stage. In the southern Piedmont area, red cedar seedlings under open canopy stands survived better than under closed canopy stands (Parker 1952). A study indicated that the height growth responses of 1-0 seedlings (one year old, not transplanted) in full sunlight were the same. Seedling growth was stunted when grown in one tenth sunlight (McDermott and Fletcher 1955). It is more sensitive to flooding than loblolly pine (Parker 1950)." (Fowells 1965)
Mice, rabbits, livestock (Albertson 1940) and deer (Van Duesen 1979) may damage seedlings. Increased stocking rates of cattle on Kansas pastures generally decrease red cedar invasion. In one study, invasion decreased especially when cattle grazed during May through October (Owensby et al. 1973). Seedling survival is usually high following transplanting (Arend 1945, Munns and Stoeckler 1946).
Established juniper plants compete directly with grassland species for moisture and nutrients (Wink and Wright 1972, Allred 1949). Eastern red cedar is potentially a problem because of the following reasons:
- Lack of fire
- Human activities increase habitat occurrences
- Many genotypes and hence wide environmental adaptability
- Plant longevity, sexual maturity in 6 to 10 years, long reproductive phase
- Efficient seed dispersal, germination and seedling vigor
- Opportunistic moisture use resulting in drought tolerance
- Evergreen growth and tolerance of temperature extremes
- Large plant size which results in shading, high moisture use, soil pH changes, higher fire tolerance, possible allelopathic effects
Active management is required to reduce populations, and to prevent invasion by maintaining vigor of grassland species.
The effectiveness of burning to control eastern red cedar is related to tree height, crown density, stand density, amount of herbaceous fuel and fire weather conditions.
Spring burns (March through May) usually kill trees up to about one meter tall (Kucera et al. 1963, Buehring 1971, Martin and Crosby 1955). Larger trees up to 20 feet (6.1 m.) occasionally are killed in some fires (Ownesby et al. 1973), or under drier, windier, and less humid conditions. In a Missouri burn in April, Kucera et al. (1963) found that 93% of all red cedar were killed; the largest tree killed was 10 feet (3.05 m.) tall. Air temperature was 63° F (17.2° C) and humidity was 21%. After another 'cooler' burn on March 31, at 53° F (11.7° C) and 43% humidity, crowns of larger plants (1.52 to 8.89 cm. in diameter at 15.24 cm. above ground) remained green (Kucera et al.1963). In Oklahoma, Dalrymple (1969) found complete control of J. ashei seedlings less than 2 feet (0.61 m.), 77% mortality of trees 2 6 feet (0.61 1.83 m.) and 27% mortality of trees greater than 6 feet (1.8 m.) (cited in Wink and Wright 1973).
In a Missouri burn, large tree mortality depended on amount of herbaceous fuel and density of crowns. Trees having crowns with sparse foliage exhibited 90% mortality. Trees having larger crowns with dense foliage showed 35% mortality. Light crowned trees had more foliage beneath them than did densely crowned trees. Temperatures the day of the burn ranged from 28-60° F ( 2.2 to 15.5° C), the lowest relative humidity was 26%, and winds averaged 4.7 mph (7.6 kms.per hour) (Martin and Crosby 1955).
For control of large trees, herbaceous fuel levels must be adequate to carry a fire. When burning large red cedar, Launchbaugh and Owensby (1978) allow for 3,3.71-4,494 kg/ha of herbaceous fuel. A 30 to 61 meter firelane is burned out when grasses are moist. After that burn is extinguished, a headfire is set when winds are about 24 km/hour and relative humidity is about 40% (Wright and Bailey 1980).
Sometimes fire will not easily carry through dense stands of red cedar, requiring additional controls such as dozing or windrowing. In Texas, a 250 ha. area of dense J. ashei was burned by a crown fire started by igniting windrows of dried juniper adjacent to the area to be burned (Bryant et al. 1983). The authors determined from this study that such areas would optimally burn when wind speeds exceed 16 km/hr, canopy cover is greater than 35%, relative humidity is between 20-40 %, air temperature is 2 to 32° C and leaf moisture is below 60% (Bryant et al. 1983).
Volatile fuels found in J. virginiana are explosive and can produce firebrands. Firebrands during a moist spring burn of J. ashei created spot fires 60 to 90 feet (18.3 to 27.4 m.) from piles of junipers. Under extremely dry conditions (81° F, 14% relative humidity, 10 to 15 mph winds = 27° C, 16.1 to 24.1 km/hr) spot fires occurred 800 to 1000 feet (243.8 m. to 304.8 m.) from the fire edge (Wright et al. 1972).
A single cut close to the ground level that removes all green foliage usually will kill red cedar (Launchbaugh and Owensby 1978). In one study, plants cut having basal diameters between 0.25 inches (0.64 cm) and 0.75 inches (1.91 cm.) showed 20% resprouting sixteen months after cutting. No regrowth occurred on plants having basal diameter larger than 0.75 inches (1.91 cm). Plants having basal diameters of 0.5 inch (1.27 cm) to 1.25 inches (3.18 cm) mowed 6 inches above ground showed 22% resprouting sixteen months after mowing. This regrowth is attributed to the presence of buds within six inches of ground level (Buehring et al. 1971).
In Missouri J. virginiana seedlings were killed by handpulling (Toney 1983). Grubbing will kill individual plants (Scifres 1980).
Most herbicides are ineffective or erratic in control of red cedar (Johnson 1979). The best results from herbicidal control are as follows:
1. Tree injection
Picloram as a potassium salt injected into trees in winter, summer and spring (Oklahoma) at rates of 1 and 3 ml. per inch (2.54 cm.) dbh (diameter breast height) killed red cedar after 14 months (Buehring et al. 1971). In an Arkansas study, picloram in an aqueous solution (1:5) injected in June provided 83% kill by the following December (Voeller and Holt 1973).
2. Soil application
Application of 10% granular picloram in August (Oklahoma) at least 3 and 6 teaspoons per inch dbh provided 90% and 70% control respectively after 13 months (Buehring et al. 1971). In Kansas, fenuro, picloram, and karbutilate applied as granules to the soil in April at 1 to 2 tablespoons per inch basal diameter showed 70 to 100% control after 23 months (Owensby et al. 1973).
3. Foliar and stem sprays
Sprays giving greater than 80% kill on trees 2 to 4 feet (0.6 to 1.2 m.) tall and 7 to 8 feet (2.13 to 2.44 m.) high included paraquat at 1 and 2 lbs./acre (1.12 and 2.24 kgs./ha) + 0.5% suffactant; dicamba at 3 and 6 lb./A (3.36 and 6.72 kg./ha) and dicamba at 2 lbs./A (2.24 kgs./ha) + 2-4-5T ester at 4 lbs./A (4.48 kgs./ha); 2-4-D + dichloropropal at 4 lbs./A (4.48 kgs./ha) each or 8 lbs./A (8.96 kgs./ha) each; and AMS at 50 and 75 lb./100 gal. (.06 and .09 kg./l) spray (Buehring et al. - 1971 from Forestry Abstracts 24(6) 1973).
4. Basal application
Hexazinone applied as an undiluted liquid in July in Virginia at 4 and 8 ml./2 inches (5.08 cm.) of basal stem diameter killed red cedar trees having basal stem diameter less than one inch (2.54 cm.) to 7 inches (17.78 cm) (Link et al. 1979).
Leaf blight (Cercospora sequoiae Ell. and Ev. var. juniperi) has killed 15 to 20 year old eastern red cedar (Scifres 1980).
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