Juniperus Linnaeus 1753

Common Names

Juniper, cedar, redcedar; cedro, sabino [Spanish] (1).

Taxonomic notes

The genus is characterised by fleshy cones with hard-shelled seeds, adaptations to avian seed dispersal; apart from this, all characters common to all of its species can also be found in other closely allied genera of Cupressaceae, notably Cupressus, Platycladus and Microbiota . About 50 species; species delimitations, particularly in central Asia, are as yet very poorly researched and this number is subject to revision (most likely downward, in view of the plethora of published names of uncertain status).

The genus is usually divided into three distinct sections or subgenera, sometimes treated as genera; descriptions of which are provided below:

  • Sect. Juniperus (syn: Juniperus sect. Oxycedrus Spach 1841)
  • Sect. Caryocedrus Endlicher 1847 (syn: genus Arceuthos Antoine 1854)
  • Sect. Sabina Spach 1841 (syn: genus Sabina Miller 1754)
Genetic monophyly has yet to be conclusively established for Juniperus and Sabina ; should they prove not to be monophyletic with respect to allied Cupressaceae genera (i.e., if fleshy cones have evolved independently in two or more ancestral taxa), acceptance of Sabina at generic rank may become necessary. Some authors (e.g. 2, 3) already do so; the traditional nomenclature in one genus is however (as here) best retained until a full genetic analysis has been carried out.

Sect. Caryocedrus is close to sect. Juniperus (several distinct characters shared), and of obvious monophyletic origin with it; future generic recognition under Arceuthos is highly unlikely.

Description

Evergreen shrubs or trees. Branchlets terete, 4-6 angled, variously oriented, but not in flattened sprays (except in J. flaccida ). Leaves in decussate (alternating) opposite pairs in 4 ranks or in alternating whorls of 3 in 6 ranks, rarely in whorls of 4 in 8 ranks. Adult leaves closely appressed to divergent, scalelike to subulate, free portion nil to 25 mm (to 32 mm recorded in J. formosana ); abaxial gland visible or not, elongate to hemispheric ( J. ashei ), sometimes exuding white crystalline deposit. Pollen cones with 3-7 pairs or trios of sporophylls, each sporophyll with 2-8 pollen sacs. Seed cones maturing in 1 or 2 years, globose to ovoid and berrylike, 3-20 mm (to 25 mm in J. drupacea ), remaining closed, often glaucous; scales persistent, 1-5 pairs or whorls of three, peltate or valvate, tightly coalesced and fused together, thick and fleshy or fibrous to obscurely woody; some sweet (e.g. J. deppeana ), many bitter and/or resinous. Seeds 1-3 per scale, round to faceted, wingless; cotyledons 2-6. Seed dispersal by frugivorous birds, which swallow the cones whole, digest the fleshy scales and pass the hard-shelled seeds undamaged through the gut; the bitter taste of many species may be related to discouraging mammalian predators of the seeds. x = 11.
  • Sect. Juniperus
Leaves not decurrent down stem, with basal abscission zone; in six rows in alternating whorls of three, mostly of 1 kind, subulate, spreading, 5-25(32) mm long, 1-2 mm wide. Winter buds present. Scale-leaves absent, except for 2 (-3) whorls of three on the cone peduncles, and 1-2 (-3) whorls as bud scales on the winter buds. Dioecious, with male and female cones on different trees. Cones axillary on shoot, on a very short 0.3-1 mm peduncle (appearing sessile); peduncle scale-leaves 1 mm. Mature female cones small to medium, 6-15 mm, scales valvate in 1 (-2) whorls of three, one whorl fertile, with 1 seed on each fertile scale, the three seeds not fused together; mature in c. 18 months from pollination.

About 7-9 species; type J. communis L. The section is divisible into two subsections, a northern group with blue-black mature cones and one broad leaf stomatal band ( J. communis and allies; 2-4 spp.), and a southern group with orange-red mature cones and two narrow leaf stomatal bands separated by the midrib ( J. oxycedrus and allies; 5 spp.).

  • Sect. Caryocedrus
Leaves as in sect. Juniperus , including basal abscission zone, except broader (2-3.5 mm wide); 10-25 mm long. Winter buds present. Scale-leaves absent, except for 3-6 whorls of three on the cone peduncles, and 2-3 whorls as bud scales on the winter buds. Dioecious, with male and female cones on different trees. Cones axillary on shoot, on 2-7 mm peduncles; peduncle scale-leaves 1.5-3.5 mm long. Mature female cones large, 18-25 mm, scales valvate in (2-) 3 (-4) whorls of three, only one whorl fertile, with 1 seed on each fertile scale, the three seeds fused together in a hard bony-textured nut 10-12 mm long; mature in c. 18 months from pollination. Type (and only species) J. drupacea Labill. The section is closely allied to sect. Juniperus and may be better treated as a subsection within it.
  • Sect. Sabina
Leaves decurrent down stem, without basal abscission zone, in four rows in decussate opposite pairs or (occasionally) in six rows in alternating whorls of 3 or eight rows in alternating whorls of 4, of three kinds: scale-like adult leaves on slow-growing and fertile shoots, 1-2 mm, adpressed or with spreading apex, free portion 0-1 mm; whip leaves on strong-growing lead shoots, subulate, spreading, free portion 0.5-2 mm; and juvenile leaves, subulate, spreading, free portion 2-10 (-13) mm. In all species, juvenile leaves are produced early in life and often also later on shaded shoots; in a few species ( J. pingii, J. procumbens, J. recurva, J. squamata ), juvenile-type leaves borne throughout life, with scale-leaves confined to cone peduncles. These and juvenile plants of other species may be distinguished from sect. Juniperus by the leaves being decurrent and lacking a basal abscission zone. Winter buds absent. Monoecious or dioecious, with male and female cones on the same or different trees depending on species. Cones terminal on 1-5 (-20) mm scale-leaved side shoots. Mature female cones small to medium, 4-18 (-20) mm, scales peltate in 2-4 (-5) decussate pairs, 1-4 (-6) scales fertile, with 1-3 seeds per fertile scale, the total 1-12+ seeds not fused together; mature in (4-) 6-18 months (possibly longer in some spp.) from pollination. About 40 species; type J. sabina L. The section is divisible into several groups based on phenology, cone characteristics and leaf margin form; precise alliances are not yet determined.

Source: (1, 6).

Range

Primarily Northern Hemisphere, one species ( J. procera ) in E Africa to 18°S. In many semiarid regions, such as through much of the western USA, northern Mexico and central & southwest Asia, it provides the dominant forest cover on large sections of the landscape. Sect. Juniperus is primarily Eurasian, with one species ( J. communis ) holarctic, the only member of the section in N. America and by far the most widespread single conifer species. Sect. Caryocedrus is a local endemic in SW Asia and SE Europe. Sect. Sabina occupies most of the range of the genus, except for Eurasia north of 50°N in Europe and 60°N in Asia.

Big Tree

The limited data I have found suggest it is J. occidentalis . Tallest may be J. drupacea , measured to c .40 m tall in Turkey (H. Karaca).

Oldest

Again, there are no data for most species, but a ages of about 2000 years has been established for J. scopulorum .

Dendrochronology

A variety of species have proven useful, delivering dendroclimatic records of up to 1000 years and providing archeological data in the American southwest. However, some species lack circuit uniformity or have a large fraction of missing rings.

Ethnobotany

Numerous cultivars of Juniperus species are widely used for landscaping (1). Because the genus is widely distributed in semiarid regions (it grows particularly well on calcareous soils) and some are not particularly palatable to domestic goats, it often affords the only tree of size on the landscape, thus providing an important source of wood for construction, fuel and other domestic uses. The wood is fragrant, usually reddish or reddish-brown, easily worked, very durable, and rarely injured by insects (5). Its resistance to decay makes it particularly useful for fenceposts and other ground-contact applications. However, it seldom achieves the size or straight grain needed in lumber. Many native peoples have used the aromatic foliage and resins for medicinal or spiritual purposes."An essential oil is obtained by distillation from wood and leaves. That from the wood is often used for perfumery, sometimes in medicine. Oil from the leaves and shoots is also used in medicine. They have powerful diuretic properties and stock should not be allowed to eat branches" (5).

Wood and/or foliage are often burned for incense in Buddhist temples.

Cones of J. communis are used for flavouring gin.

Observations

See the respective species. Please inform me if you know of any arboreta with exceptional Juniperus collections.

Remarks

Juniperus is an old Latin name used by Virgil and Pliny (2).

"Mutants, or "sports," affecting plant habit and foliage are present in all species and are likely related to single-gene mutations. Many have been given formal names or incorrectly ascribed to hybridization. Gymnocarpy (bare seeds protruding from the cone), caused by insect larvae (4), is occasionally found in most junipers, particularly in the southwestern United States. Specimens with such aberrations may be almost impossible to identify without chemical data" (1).

Citations

(1) Adams, Robert P. in Flora of North America online .
(2) Weber 1987 .
(3) Cheng & Fu 1987 .
(4) Zanoni 1978 .
(5) Dallimore & Jackson 1967 .
(6) M.P. Frankis, personal observations, text prepared for this page.

See also:
Fassett 1945 .
Van Haverbeke 1968 .
Vasek 1966 .
Zanoni & Adams 1979 .
R.P. Adams. 1969. Chemosystematic and numerical studies in natural populations of Juniperus . Ph.D. dissertation, University of Texas.
R.P. Adams and T.A. Zanoni. 1979. The distribution, synonymy, and taxonomy of three junipers of the southwest United States and northern Mexico. Southwest Naturalist 24:323-330.
R.P. Adams, E. von Rudloff and L. Hogge. 1983. Chemosystematic studies of the western North American junipers based on their volatile oils. Biochem. Syst. & Ecology 11:85-89.
M.T. Hall. 1952. Variation and hybridization in Juniperus. Annals of the Missouri Botanical Garden 39:1-64.

This page co-edited with M.P. Frankis, Mar-1999.

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This page is from the Gymnosperm Database
URL: http://www.geocities.com/~earlecj/cu/ju/index.htm
Edited by Christopher J. Earle
E-mail: earlecj@earthlink.com
Last modified on 25-Jan-2000

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