Juniperus silicicola (Small) Bailey
Cupressaceae -- Cypress family
L. P. Wilhite
Southern redcedar (Juniperus silicicola), also called redcedar, coast juniper, sand-cedar, and eastern redcedar, has not been well studied. Until more work is done, the fragmentary information available should be supplemented, though cautiously, with information in the literature about eastern redcedar (J. virginiana). The two species are similar in many respects. Generally, eastern redcedar has ascending or horizontal branches, male cones 3 to 4 mm (0.12 to 0. 16 in) long, and female cones 5 to 6 mm (0.20 to 0.24 in) long containing one to four seeds. In contrast southern redcedar generally has more slender, pendulous branches, male cones 5 to 6 mm (0.20 to 0.24 in) long, and female cones 3 to 4 mm (0.12 to 0.16 in) long containing only one or two seeds (5,11).
The native range of southern redcedar extends from coastal North Carolina through northern Florida and across the Gulf Coast to eastern Texas. Except in the center of the Florida peninsula and in outliers in Louisiana and Texas, the species is found within 50 km (30 mi) of saltwater.
On the range map, the inland boundary of the species should not be considered exact because it touches or overlaps the southern boundary of eastern redcedar, which so resembles southern redcedar that the two often are confused.
- The native range of southern redcedar.
Two climatic types, humid and moist subhumid, are present within the range of southern redcedar. Normal precipitation increases from about 1200 mm (48 in) per year in the Carolinas to more than 1600 mm (63 in) along the central Gulf Coast, then decreases to about 1000 mm (40 in) in eastern Texas. Length of growing season varies from about 240 days in North Carolina, Louisiana, and Texas to more than 330 days along both coasts of central peninsular Florida. Southern redcedar is found from slightly north to slightly south of U.S. Department of Agriculture Plant Hardiness Zone 9, which is defined by a range in average minimum temperatures from -7° to -1° C (20° to 30° F).
Southern redcedar is mostly restricted to the nearly flat outer Coastal Plain, so its establishment and growth in relation to topographic factors are not well understood.
Along the Atlantic and Gulf Coasts, southern redcedar is associated with limestone outcroppings and Indian shell middens bordering tidal marshes, and on sea islands on the leeward side of dunes, where salt spray is minimal. On the Gulf Coast, the species often is found in a narrow zone between the tidal marsh and the pine flatwoods (7). Also along the Gulf Coast, it often colonizes dredge spoil islands (3).
Inland from the coast, scattered individuals of the species can be found from the broad, flat ridges between streams to the flood plains of these streams. In areas of abandoned rice fields in South Carolina, the species is found more frequently on the tops and sides of the old dikes than in the poorly drained flats between them.
The natural range of southern redcedar includes soils belonging to the orders of Alfisols, Entisols, Inceptisols, Spodosols, and Ultisols (14). Redcedars usually are found on soils that are moist or wet, but not saturated. In general, the species appears to prefer sites of high base saturation, as indicated by its presence near sources of limestone or on Alfisols.
Southern redcedar is the predominant species in the forest cover type Southern Redcedar (Society of American Foresters Type 73), in which it occupies a plurality (20 to 50 percent) of the basal area (4). Common overstory associates in this type are live oak (Quercus uirginiana), sand live oak (Q. uirginiana var. germinata), cabbage palmetto (Sabal palmetto), slash pine (Pinus elliottii), southern magnolia (Magnolia grandiflora), laurel oak Quercus laurifolia), redbay (Persea borbonia), and American holly (Ilex opaca). Common understory species are yaupon (I. vomitoria), southern bayberry (Myrica cerifera), devilwood (Osmanthus americanus), Carolina laurelcherry (Prunus caroliniana), beautyberry (Callicarpa americana), bumelia (Bumelia spp.), tree sparkleberry (Vaccinium arboreum), muscadine grape (Vitis rotundifolia), and greenbriers (Smilax spp.).
Southern redcedar was virtually eliminated as an overstory species during the 19th century by harvesting, primarily for the manufacture of pencils. Live oaks and other associated trees were not cut at that time, and their competition presumably has retarded the reestablishment of cedar-dominated stands. Consequently, Southern Redcedar (Type 73) is quite similar to Cabbage Palmetto (Type 74). Both of these types are variants of a general maritime forest.
Inland from this maritime forest, the Southern Redcedar type sometimes intergrades with Sweetbay-Swamp Tupelo-Redbay (Type 104). Southern redcedar is listed as a minor species in Slash Pine (Type 84), and it has been found in Loblolly Pine (Type 81). In these pine types, redcedars seldom reach the overstory, possibly because of competition from the pines and associated hardwoods.
Flowering and Fruiting- Southern redcedar is dioecious. The male cones shed pollen in January to February, and the berrylike female cones, dark blue and covered with a glaucous bloom, mature in October to November of the first year (11). Seeds often have dormant embryos, and germination may not occur until the second or third spring after seed maturation (2). Cold stratification, however, hastens germination, and so might stratification of the seed by passage through the digestive system of an animal. Germination is epigeal. Southern redcedar should be sown in fall or cold-stratified and sown in either fall or spring (13).
Seed Production and Dissemination- There is considerably more information on the reproduction of eastern redcedar than on southern redcedar. Eastern redcedar produces some seeds nearly every year with irregular heavy seed crops. Its seeds are dispersed in the fall, usually by birds. Seeds may be stored as dried fruits or after extraction with a macerator. Cleaned seeds range from 81 600 to 121 300/kg (37,000 to 55,000/lb). A citric acid soak preceding cold stratification increases germination more than cold stratification alone (13).
Seedling Development- Stratified seeds of eastern redcedar sown in the spring should be in the ground early enough to ensure complete germination before air temperatures exceed 21° C (70° F), and complete germination requires 4 to 5 weeks. Juniper seeds are usually drilled into rows 15 to 20 cm (6 to 8 in) apart and covered with about 0.6 cm (0.25 in) of firmed soil. The beds should be mulched with straw, sawdust, burlap, or plastic film, and the mulch removed as soon as germination starts. Light shade should be provided during the first growing season. Eastern redcedar is planted as 2-0, 3-0, 1-1, 1-2, 2-1, or 2-2 stock. Potting or balling for field planting increases survival over bare-root planting during dry years (13).
Vegetative Reproduction- Southern redcedar can be propagated by cuttings of nearly ripened wood (2). The closely related species, eastern redcedar, can be propagated by rooted cuttings, but there is much variability among varieties within the species as to ease of rooting. Rooting success has been increased by treatments with indolebutyric acid, naphthalene acetic acid, and Phygon XL talc. Because of the difficulties and inconsistencies in rooting juniper cuttings, grafting has long been the standard method of propagating clonal material of eastern redcedar (18).
Growth and Yield- Little is known about the growth of this species. It has been reported to be moderate in growth rate (1) or to be long lived and slow growing (17). Mature height has been reported to be about 8 m (25 ft) (1,2,19) or about 15 m (50 ft) (9,12). The largest southern redcedar recorded by the American Forestry Association was 21 m (70 ft) tall and 145 cm (57 in) in d.b.h. in 1976 (10). Some of the virgin timber along Apalachee Bay in Florida may have been more than 30 m (100 ft) tall (3,4). Perhaps the second-growth timber of this long-lived species has not yet reached its mature height on its best sites.
Rooting Habit- The species has been reported to have a shallow root system (17).
Reaction to Competition- Brief statements in the literature, plus observations, indicate that southern redcedar can become established and will grow in sun or partial shade. Competition, however, may retard reestablishment of cedar-dominated maritime forests because of the dense shade cast by live oaks and associated hardwoods. Southern redcedar, like eastern redcedar, is classed as intolerant to very intolerant of shade. The fact that southern redcedar often grows on the margins of tidal marshes indicates that it is fairly tolerant of salt spray, wind, and flooding (1,12,17).
Damaging Agents- Fire is deleterious to this thin-barked species, but the forest cover type Southern Redcedar, which is generally found on sea islands or immediately inland from salt marshes of the mainland, rarely experiences fire. Farther inland, where southern redcedar occurs as a minor species and fires are more frequent, it suffers damage and mortality. Fire damage may be less prevalent now than in the past. Control of wildfires has allowed eastern redcedar to come back to sites within its natural range where it has not existed for a long time (18), and conditions are similar for southern redcedar within its natural range.
Cedar-apple rust (Gymnosporangium juniperi-virginianae) attacks southern redcedar (6), and bagworms (Thyridopteryx ephemeraeformis) have been observed feeding on its foliage. Other agents that damage eastern redcedar, such as cedar blight (Phomopsis juniperovora) and various wood rots (15), probably damage southern redcedar also.
Southern redcedar lumber is used in the manufacture of chests, wardrobes, closet linings, flooring, and scientific instruments. Because the heartwood of redcedar is very resistant to decay, it is used for fence posts (16). Young southern redcedars are sold as Christmas trees (2).
Junipers, including southern redcedar, furnish fruit, browse, and protective and nesting cover for many species of wildlife (8).
In landscaping, southern redcedar is used as a background, windbreak, or hedge in parks and along roadsides or around homes (1,2). Although usually found on moist soil, it will grow in dry, sandy, or rocky land, and this hardiness, plus its salt tolerance, makes it desirable for ocean bluffs and seaside plantings.
Southern redcedar apparently hybridizes freely with eastern redcedar (18). The literature contains nothing else on the genetics of southern redcedar.