Juniperus communis L.
|Author: Judith Ladner|
Juniper, Common juniper, Fairy circle, Hackmatack, Horse savin, Gorst, Aiten, Dwarf juniper, Mountain common juniper, Old field common juniper, Prostrate juniper, GenÚvrier (France), Ginepro (Italy), Enebro (Spain), Gemeiner Wachholder (Germany, Switzerland), Reckholder (Switzerland)
Juniperus communis L. is a coniferous evergreen shrub or a small columnar tree, multistemmed, decumbent or rarely upright. The crown is generally depressed. It grows very slowly. The morphological characteristics including growth form differ somewhat according to variety. Adventitious root development can occur when branches come in contact with the ground become buried. Juniper has a thin, brown, fibrous bark which exfoliates in thin strips. The branches are spreading or ascending; branchlets are erect. Twigs are yellowish or green when young, turn brown and harden with age. The leaves are simple, stiff and arranged in whorls of three with pungent odour. They are green but sometimes appearing silver when glaucous, spreading; abaxial glands are very elongate. The adaxial surface has a glaucous stomatal band. The apex is acute to obtuse, mucronate. Young leaves tend to be more needlelike whereas mature leaves are scalelike. The fruits are berrylike seed cones. They have straight peduncles and are of globose to ovoid shape, 6-13 mm, red at first, ripening to a glaucous bluish black, resinous to obscurely woody. Male stroboli are sessile or stalked, and female strobili are made up of green, ovate or acuminate scales. Juniper berries take two or three years to ripen, so that blue and green berries occur on the same plant. Each cone has 2-3 seeds of 4-5 mm. The seeds require a period of cold stratification. 2n=22. Individuals can live for more than 170 years.
This species grows on dry, open, rocky, wooded hillsides, sand terraces, maritime escarpments, and on exposed slopes and plateaus. It is found on dunes or dune heath in coastal areas, on isolated mountains, and may spread into fields and pastures. Establishment is more likely in open spaces between older shrubs and may be favored by grazing. Juniperus communis L. grows in hilly to alpine regions up to an altitude of more than 3000 m. Common juniper is intolerant of shade, found in open environments; colonizing plants reach maximum abundance on harsh, stressed environments in which competition is lacking. It grows on poor sites, tolerates full sun and wind and is pH adaptable.
Generally common juniper is killed or seriously damaged by fire; the relatively long germination period and poor germination rates contribute to slow postfire reestablishment.
Common juniper may occur in association with the following species:
Juniper is cold-tolerant but the young growth in spring can be damaged by late frosts.
Juniperus communis L. requires dry or moist soil and can tolerate drought.
This species grows on a variety of soil types including acidic and calcareous sands, loams, or marls. It prefers light (sandy), medium (loamy) and heavy (clay) soils and is tolerant of ultramafic soils. The Europe common juniper is restricted to well-aerated soils somewhat deficient in both nitrogen and phosphorus.
Common juniper is widely distributed in the Northern Hemisphere. It is circumboreal across Europe, North Africa, North America, northern and western Asia and Japan.
Juniperus communis L. and other juniper species may become invasive, severely reduce forage production and interfere with handling and movement of livestock. Methods of controlling juniper woodlands are mechanical clearing with bulldozers, cables, chains, and motorized saws, by burning, and by herbicides (Janknecht 1986). But costs are high and effects often low; regrowth of trees and shrubs on treated areas often led to even denser stands, since juniper is almost instantly re-disseminated by birds (Daubenmire 1978). Juniper bushes provide an important food source and cover for many species of bird, in a landscape that is often devoid of trees and shrubs (McBride & Borders Forest Trust 1998). In some regions like north-east England continual heavy grazing opened up dense stands of juniper, gradually fragmenting colonies into an open park-like community of scattered individuals. In this situation regeneration does not occur and the population gradually dies out (Barrett 1998). Juniper habitats were included in the EC Habitat and Species Directive (European Community 1992), acknowledges the threatened status of juniper in the European context.
Common pests are the Juniper Webworm (Gelechiidae: Dichomeris marginella), the Bagworm (Psychidae: Thyridopteryx ephemeraeformis), the Spruce Spider Mite (Tetranychidae: Oligonychus ununguis) and the Juniper Scale (Diaspididae: Carulaspis juniperi). Several juniper cultivars are highly susceptible to lesion nematode (Pratylenchus sp.).
Juniperus communis L. is susceptible to juniper twig blight (Phomopsis juniperovora), Phytophthora root rot (Phytophthora cinnamomi) and cedar-apple type rusts (Gymnosporangium species).
This species propagates by seed which require a specific period of rest after ripening. Ideal germination conditions are moist, compact soil with sufficient oxygen diffusion. The seeds are dispersed by gravity, water, birds, or mammals. Digestive processes may enhance germination, therefore junipers are often established along the line of sheep tracks that became unused (McBride & Borders Forest Trust 1998). The age of the bushes has been shown to affect the reproductive capacity as the viabilty of seed reduces from 80% in young stands to 5% in older populations. Attempts at hand seeding under greenhouse conditions (for ornamental plant production) has been largely unsuccessful. Cultivars may be propagated by cuttings. Juniper is very slow to establish and develop. It may take 20 years for a bush to reach 1 m tall (Barrett 1998).
Varieties: communis, depressa, hemisphaerica (J. Presl & C. Presl), parlatore, megistocarpa, montana, and oblonga
Cultivars: Aurea, Aureo-spica, Cracovia, Depressa Aurea, Dumosa, Effusa, Hibernica, Oblonga pendula, Pencil Point, Prostrata, Pyramidalis, Repanda, Saxatilis, Saxatilis pallas, Suecica, and Suecica nana
Volatile oil (0.2 to 3.4%), proanthocyanidines, flavonoids, lignan desoxypodophyllotoxin and its isomer desoxypicropodophyllotoxin, diterpene acids, sesquiterpenes, sugars, resin, vitamin C.
Medicinal use of the fruits: The ripe, unshrivelled berries should be collected in autumn and dried slowly in the shade, to avoid losing the oil. Indications: diuretic, antiseptic, aromatic, rubefacient, stomachic and antirheumatic. Traditional use includes cystitis, flatulence and colic. The oil mixed with lard is also used in veterinary practice (EMEA 1999). The essential oil present is quite stimulating to the kidney nephrons and so this herb should be avoided in kidney disease and during pregnancy. Juniper tincture is applied topically for some skin donditions and baldness. Various extracts of Juniperus communis L. have for up to 63.3 higher inhibitory effect on certain kinds of bacteria than penicillin.
Other uses: Juniper is also used for flavouring food (sauerkraut, stuffings, vegetable pates etc.) and beverages (tea, gin). The roasted seed is a coffee substitute. The wood is fine grained, durable, and reddish with white sapwood but currently it has no commercial value. It could be used for different purposes: fuel (especially for pellet-stoves), firewood, fenceposts, cement and particle boards, wall board, cordwood housing, parquet, paper, chemical derivatives, activated carbon and small wood items. Juniper wood has an outstanding ability of resisting decay and insects even when exposed to the soil. This resinous wood yields much more tar than drier ones. Therefore, juniper wood should make an excellent wood preservative. There are different problems concerning the use of juniper wood: The trees often develop an irregular and unsymmetrical growth making the production of some products more difficult. Another problem is the thick and cracked bark which contains dust and sand and even forms enclosures within the solid wood. A possible solution should be to first chip the complete wood right after the harvesting and then remove the bark chips from the mixture. The use of juniper in the chemical industry and in pharmacology is difficult because the substances that form cade oil are more easily and cheaper yielded by synthesis. Further, the portion of a certain substance within wood varies with the area, the soil, the single plant, and even with the part of the plant, thus making an efficient mechanized process almost impossible (Janknecht 1986). Juniper is highly valued as an ornamental shrub. It provides good ground cover even on stony or sandy sites. In rehabilitation of disturbed sites, common juniper has low value for short-term projects but moderate to high value for long-term projects (Dittberner & Olson 1983). Juniperus communis L. may be also used as insect repellent and in cosmetic industry.
Indigenous peoples from Eurasia made tonics for kidney and stomach ailments and rheumatism. Juniper was used by Great Basin Indians as a blood tonic. Native Americans from the Pacific Northwest used tonics made from the branches to treat colds, flu, arthritis, muscle aches, and kidney problems. In Sweden a beer is made that is regarded as a healthy drink. In hot countries the tree yields by incision a gum or varnish.
Common juniper is rated as poor in overall protein and energy value (Dittberner & Olson 1983). It is very rarely grazed by domestic animals (U.S. Department of Agriculture 1937). Experimental data even support the conclusion that isocuressic acid, a constituent of juniper, is an abortifacient compound for cattle (Gardner et al. 1998). Wild ungulates generally eat only trace amounts of common juniper while it can become an important winter food for some species (Dietz & Nagy 1976) (Gastler et al. 1951) (Novak 1959) (Pase & Hurd 1958) (Mundinger 1978) (Mundinger 1979). However, cones of most junipers are eaten by many species of birds and mammals (Philips 1910) (Catling & Brownell 1998) (Decker et al. 1991).
Barrett 1998; Catling & Brownell 1998; Daubenmire 1978; Decker et al. 1991; Dietz & Nagy 1976; Dittberner & Olson 1983; EMEA 1999; European Community 1992; Gardner et al. 1998; Gastler et al. 1951; Janknecht 1986; McBride & Borders Forest Trust 1998; Mundinger 1978; Mundinger 1979; Novak 1959; Pase & Hurd 1958; Philips 1910; U.S. Department of Agriculture 1937