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Juniperus


Juniperus communis shrubs


Plant Characteristics
Lifespan: ⌛ perennial
Cultivation
Features: ✓ evergreen
Scientific Names

Cupressaceae >

Juniperus >

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Junipers are coniferous plants in the genus Juniperus of the cypress family Cupressaceae. Depending on taxonomic viewpoint, there are between 50-67 species of juniper, widely distributed throughout the northern hemisphere, from the Arctic, south to tropical Africa in the Old World, and to the mountains of Central America in the New World.

Cones and leaves of Juniperus communis

Junipers vary in size and shape from tall trees, 20-40 m tall, to columnar or low spreading shrubs with long trailing branches. They are evergreen with either needle-like and/or scale-like leaves. They can be either monoecious or dioecious. The female seed cones are very distinctive, with fleshy, fruit-like coalescing scales which fuse together to form a "berry"-like structure, 4-27 mm long, with 1-12 unwinged, hard-shelled seeds. In some species these "berries" are red-brown or orange but in most they are blue; they are often aromatic (for their use as a spice, see juniper berry). The seed maturation time varies between species from 6-18 months after pollination. The male cones are similar to those of other Cupressaceae, with 6-20 scales; most shed their pollen in early spring, but some species pollinate in the autumn.

Detail of Juniperus chinensis shoots, with juvenile (needle-like) leaves (left), and adult scale leaves and immature male cones (right)

Many junipers (e.g. J. chinensis, J. virginiana) have two types of leaves: seedlings and some twigs of older trees have needle-like leaves 5-25 mm long; and the leaves on mature plants are (mostly) tiny (2-4 mm long), overlapping and scale-like. When juvenile foliage occurs on mature plants, it is most often found on shaded shoots, with adult foliage in full sunlight. Leaves on fast-growing 'whip' shoots are often intermediate between juvenile and adult.

In some species (e.g. J. communis, J. squamata), all the foliage is of the juvenile needle-like type, with no scale leaves. In some of these (e.g. J. communis), the needles are jointed at the base, in others (e.g. J. squamata), the needles merge smoothly with the stem, not jointed.

The needle-leaves of junipers are hard and sharp, making the juvenile foliage very prickly to handle. This can be a valuable identification feature in seedlings, as the otherwise very similar juvenile foliage of cypresses (Cupressus, Chamaecyparis) and other related genera is soft and not prickly.

Juniper is the exclusive food plant of the larvae of some Lepidoptera species including Bucculatrix inusitata and Juniper Carpet and is also eaten by the larvae of other Lepidoptera species such as Chionodes electella, Chionodes viduella, Juniper Pug and Pine Beauty.


Read about Juniperus in the Standard Cyclopedia of Horticulture 

Juniperus (ancient Latin name). Pinaceae. Juniper. Ornamental trees and shrubs grown for their foliage and habit.

Evergreen, with the branchlets spreading in all directions: lvs. either all needle-shaped and in 3's, or needle-shaped and scale-like, and usually opposite, often found on the same plant, the needle-shaped lvs. prevailing on younger plants and vigorous branches, the scale-like ones on older plants: fls. dioecious, rarely monoecious; staminate yellow, consisting of numerous anthers united into an ovoid or oblong catkin; pistillate greenish, minutely globular, with several bracts, each or some bearing 1 or 2 ovules; the bracts become fleshy and unite into a berry-like cone, usually wholly inclosing the 1-6, rarely 12, seeds. The fr. ripens either the first year, as in J. virginiana, or the second, as in J. Sabina and most species, or in the third, as in J. communis.—About 40 species distributed throughout the extra-tropical regions of the northern hemisphere, in Amer. south to Mex. and W. India. Juniperus is closely allied to Cupressus, and sometimes hard to distinguish without fr.; but young plants with needle- shaped lvs. can be almost always told apart, since Juniperus has whitish lines or marks on the upper surface of the lvs., while the similar juvenile forms of allied genera have the whitish marks beneath. Most species are very variable, as well in habit as in the shape of the lvs., which renders the determination of an unknown form, at least without fr., a rather difficult task.

The junipers vary greatly in habit from tall pyramidal trees to low prostrate or trailing shrubs, and have small needle-shaped or scale-like foliage, insignificant flowers and small berry-like fruits usually bluish black and often glaucous, less often brown or orange. Many of the species are hardy North, as J. virginiana, J. scopulorum, J. communis, J. rigida, J. Sabina, J. chinensis, J. Pseudo-sabina, J, sphaerica, J. squamata; others are half-hardy, as J. Oxycedrus, J. macrorarpa, J. recurva, J. excelsa, J. occidentalis, while some, as J. procera, J. Lucayana, J. thurifera and the Mexican species, can only be grown South. All are valuable ornamental plants, and the erect-growing species, mostly of pyramidal or columnar habit, are decorative as single specimens on the lawn or if planted in groups. Some varieties form a very narrow column, and are valuable for formal gardens; the columnar form of J. virginiana is a good substitute in the North for the classical cypress. The low prostrate junipers, as J. communis var. montana, J. horizontalis, J. sabina, and J. squamala, are well adapted for covering rocky slopes or sandy banks. The close-grained, fragrant wood is much used for the interior finish of houses and in the manufacture of small articles, also for posts, since it is very durable in the soil; that of J. virginiana and J. Lucayana is in great demand for pencil-making. The fruits and also the young branchlets of some species contain an aromatic oil used in medicine. The fruit of J. drupacea is edible.

The junipers thrive best in sandy and loamy, moderately moist soil, but grow well even in rather dry, rocky and gravelly ground. They prefer sunny, open situations. They are well adapted for hedges and for planting as shelter or windbreaks; also for seaside planting. Propagation is by seeds, which germinate usually the second and sometimes the third year; to hasten their germination, they may be plunged for 3 to 6 seconds in boiling water, but this should be regarded as an experiment and tried only with a portion of seed. They, are also increased by cuttings of nearly ripened wood in fall under glass, either outdoors or in the greenhouse. As a rule, those with needle-shaped leaves root much more easily than those with scale-like leaves, and the latter are therefore mostly increased by side-grafting during the winter in the greenhouse on young potted plants of the typical form or an allied species. The shrubby species, especially J. Sabina, are also propagated by layers.

The above text is from the Standard Cyclopedia of Horticulture. It may be out of date, but still contains valuable and interesting information which can be incorporated into the remainder of the article. Click on "Collapse" in the header to hide this text.


Cultivation

Propagation

Pests and diseases

Species

The number of juniper species is disputed, with two recent studies giving very different totals, Farjon (2001) accepting 52 species, and Adams (2004) accepting 67 species. The junipers are divided into several sections, though (particularly among the scale-leaved species) which species belong to which sections is still far from clear, with research still on-going. The section Juniperus is an obvious monophyletic group though.

 
Juniper needles, magnified. Left, Juniperus communis (Juniperus sect. Juniperus; note needles 'jointed' at base). Right, Juniperus chinensis (Juniperus sect. Sabina; note needles merging smoothly with the stem, not jointed at base).
 
Juniperus phoenicea on El Hierro, Canary Islands
 
An Eastern Juniper in October laden with ripe cones.

Standard Cyclopedia

Index. albo-spicata, 16. albo-variegata,14,16 alpina, 6. argentea, 14. aurea, 6, 14. aureo-variegata,6,14. australis, 18. barbadensis, 18,19. bedfordiana, 18. bermudiana, 19. californica, 10. canadensis, 6. cannartii, 16. Cedrus, 3. chamberlaynii, 16. chinensis, 14. communis, 6. cupressifolia, 20. densa, 7. depressa, 6. douglasii, 21. drupacea, 1. dumosa, 16. elegantissima, 16. excelsa, 12. fargesii, 8. fastigiata, 6, 20. femina, 14. fortunei, 15. glauca, 15, 16. giobosa, 16. hemisphaerica, 6. hibernica, 6. horizontalis, 21. humilis, 20. jackii, 6. japonica, 14. lucayana, 18. macrocarpa, 2. mascula, 14. Montana, 6. nana, 6. neaboriensis, 2. oblonga, 6. oblong-pendula, 6, and suppl. occidentalis, 11. oxycedrus, 4. pendula, 3,6,14,16. pfitseriana, 14. phoenicea, 9. plumose, 16. procera, 13. procumbens, 14,21. prostrata, 21. pyramidalis, 14,16. recurva, 7,8. reevesii, 14. reflexa, 6. repanda, 7. repens, 21. reptans, 16. rigida, 5. sabina, 20. sabinoides, 20 and suppl. schottii, 16. scopulorum, 17. shephardii, 17. sibirica, 6. sinensis, 14. sphaerica, 15. squamata, 8. stricta, 6,12. suecica, 6. tamariscifolia, 20. tripartite, 16. variegate, 12, 20. venusta, 16. virginiana, 16,18.

J. conferta, Parl.=J. litoralis.—J. davurica, Pall. Allied to J. Sabina. Procumbent, with slender, spreading or drooping branchlets: fr. l-4-seeded, small. Siberia.—J. flaccida, Schlecht. Graceful tree, to 30 ft., with spreading branches and slender, remote, pendulous branchlets: lvs. acute, with spreading tips: fr. globular, 5-10- seeded. Texas, Met S.S. 10:519.—J.fatidlisima, Willd. Allied to J. excelsa. To 12 ft. high: branchlets thicker: lvs. with spreading apex, mucronate, usually eglandular: fr. larger, l-2-seeded. Greece, W. Asia.—J. formosana, Hayata (J. taxifolia Parl., not Hook. & Am. J. oblongo-pendula, Hort.). Allied to J. rigida. Tree, to 40 ft.: lvs. rigid, spiny-pointed, with 2 white bands above, ½ -l in. long: fr. ovoid, orange, . across. Formosa, Cent. & W. China. Has proved hardy at the Arnold Arboretum; the true J. taxifolia, Hook. & Arn. is not in cult.—J. litoralis. Max. (J. conferta, Parl.). Allied to J. rigida, but prostrate, with long, trailing branches: fr. larger. Japan.—J. macropoda, Boiss. Allied to J. excelsa. Shrub or small tree, to 30 ft., sometimes procumbent: lvs. closely appressed: fr. nodding, globular, 4-seeded. Persia to Himalayas.—J. mogalocdrpa, Sudworth. Allied to J. californica. Tree 30-50 ft. with a single trunk: lvs. in 3'a, acute: fr. 1/2in across or slightly more, 1-2-seeded. Ariz.—J. mexicana, Schiede. Pyramidal tree: branchlets numerous, short and rather stout: lvs. acute, loosely appressed: fr. 2—4-seeded. Mex.—J. mexicana, Schlecht.=J. tetragona.—J. monosperma, Sarg. (J. occidentalis var. monosperma, Engelm.). Closely allied to J. occidentalis. Branchlets more slender: lvs. usually opposite and eglandular: fr. smaller and usually 1-seeded. Rocky Mts.. from Colo, to New Mex. S.S. 10:522.—J. obldngo- p&ndulti, Hort.=J. formosana.—J. pachjIphlaea, Torr. Tree, to 60 ft. allied to J. occidentalis. with broad, pyramidal or round-topped head: lvs. usually opposite, glandular, bluish green: fr. dark reddish brown, bloomy, with 3-4 seeds. Has a checkered bark like a black-jack oak. Colo, to Texas and New Mex. S.S. 10:520.—J. Pinchotii, Sudworth. Allied to J.californica. Small tree to 20 ft., usually with several sts.: branchlets rather slender: lvs. usually in 3's, appressed, sharply pointed, yellowish green fr. globose or ovoid, 1/3in. long, red, 1-2-seeded. Texas. B.T. 110-J Paeudo-sabina. sch. & Mey. Allied to J. Sabina. Erect shrub, with thick, dense and short branchlets: lvs. usually dimorphic: fr. ovate, blackish, glossy, 1-seeded. Siberia.—J. sabinmdes, Endl.=J. thurifera.—J. sabinoides, Nees=J. tetragona.J. sabinoides, Griseb.=J. Sabina var. tamariscifolia.—J. saltuaria, Rehd. & Wilaon. Allied to J. Pseudo-sabins. Tree to 40 ft.: lvs. dark green, dimorphic, those of the lateral branches scale-like, obtusiah, of the shoots in 3's, acute: fr. erect, ovoid, 1/4in. long, 1-seeded. N.W.China.—j sanderi, Hort.=Chamaecyparis obtuse var. ericoides.—J. tazifolia, Parl.=J. formosana.—J. tttrdgona, Schlecht. Allied to J. occidentalis. Small tree, to 20 ft., rarely to 40 ft., with round-topped or pyramidal head and slender, quadrangular branchleta: Ivs. ootuae, usually eglandular: fr. subglobose. mostly 1-seeded. Texas to Mex. S.S. 10:523.—J. thurlfera. linn. Shrub or tree, to 40 ft, with round-topped head and spreading branches: branchlets slender: fr. globular, 2-3-seeded. Spain, Algeria.—J. utahensis,lemm. (J. californica var. utahensis, Engelm.). Bushy tree, rarely more than 20 ft., with broad, open head: branchlets slender: lvs. obtuse, light yellowish green: fr. usually 1-seeded. Colo, to Calif., west to Utah. S.S. Alfred Rehder.

Gallery

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  • photo 3

References

External links


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