Junipers are coniferous trees and shrubs in the genus Juniperus ( joo-NIP-ər-əs) of the cypress family Cupressaceae. Depending on the taxonomy, between 50 and 67 species of junipers are widely distributed throughout the Northern Hemisphere as far south as tropical Africa, as far north as the Arctic, and parts of Asia and Central America. The highest-known juniper forest occurs at an altitude of 4,900 metres (16,100 ft) in southeastern Tibet and the northern Himalayas, creating one of the highest tree lines on earth.
Description
Junipers vary in size and shape from tall trees, 20–40 metres (66–131 feet) tall, to columnar or low-spreading shrubs with long, trailing branches. They are evergreen with 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 berrylike structure (galbulus), 4–27 millimetres (3⁄16–1+1⁄16 inches) long, with one to 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 and can be used as a spice, most famously in gin. The seed maturation time varies between species from 6 to 18 months after pollination. The male cones are similar to the other Cupressaceae, with 6 to 20 scales. In hardiness zones 7 through 10, junipers can bloom and release pollen several times each year. Different junipers bloom in autumn, while most pollinate from early winter until late spring.
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 (3⁄16–1 in) long, on mature plants the leaves are overlapping like (mostly) tiny scales, measuring 2–4 mm (3⁄32–5⁄32 in). 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, while in others (e.g., J. squamata), the needles merge smoothly with the stem. 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 are soft and not prickly. Junipers are gymnosperms, which means they have seeds, but no flowers or fruits. Depending on the species, the seeds they produce take 1–3 years to develop. The impermeable coat of the seed keeps water from getting in and protects the embryo when dispersed. It can also result in a long dormancy that is usually broken by physically damaging the seed coat. Dispersal can occur from being swallowed whole by frugivores and mammals. The resistance of the seed coat allows it to be passed down through the digestive system without being destroyed along the way. These seeds last a long time, as they can be dispersed long distances over the course of a few years.
Classification
Sections The genus has been divided into sections in somewhat different ways. A system based on molecular phylogenetic data from 2013 and earlier used three sections:
Section Caryocedrus – 1 species with large, blue, woody, 3-seeded cones; native to the Mediterranean Section Juniperus – 14 species with blue or red seed cones, often with 3 seeds; 12 species native to the Eastern Hemisphere, one endemic to North America, and one species, J. communis, circumboreal Section Sabina – about 60 species with variously coloured seed cones with 1 to 13 seeds; species about equally divided between the eastern and western hemispheres Juniperus sect. Sabina was further divided into clades. A new classification of gymnosperms published in 2022 recognised the sections as three separate genera: Arceuthos for section Caryocedrus, Sabina for section Sabina, and Juniperus sensu stricto for section Juniperus.
Species
Juniperus sect. Caryocedrus Cones with three seeds fused together; needles with two stomatal bands. One species:
Juniperus drupacea – Syrian juniper
Juniperus sect. Juniperus Needle-leaf junipers; the adult leaves are needle-like, in whorls of three, and jointed at the base. Species:
Juniperus sect. Juniperus subsect. Juniperus – cones with three separate seeds; needles with one stomatal band Juniperus communis – common juniper Juniperus communis subsp. alpina – alpine juniper Juniperus conferta, syn. Juniperus rigida var. conferta (Parl.) Patschke – shore juniper Juniperus rigida – Temple juniper or needle juniper Juniperus sect. Juniperus subsect. Oxycedrus – cones with three separate seeds; needles with two stomatal bands Juniperus brevifolia – Azores juniper Juniperus cedrus – Canary Islands juniper Juniperus formosana – Chinese prickly juniper Juniperus lutchuensis, syn. Juniperus taxifolia var. lutchuensis (Koidz.) Satake – Ryukyu juniper Juniperus oxycedrus – Western prickly juniper, cade juniper Juniperus macrocarpa – large-berry juniper
Juniperus sect. Sabina Scale-leaf junipers; adult leaves are mostly scale-like, similar to those of Cupressus species, in opposite pairs or whorls of three, and the juvenile needle-like leaves are not jointed at the base (including in the few that have only needle-like leaves; see below right).
Old World species
Juniperus chinensis – Chinese juniper Juniperus convallium – Mekong juniper Juniperus excelsa – Greek juniper Juniperus foetidissima – stinking juniper Juniperus indica – Himalayan black juniper Juniperus komarovii – Komarov's juniper Juniperus phoenicea – Phoenicean juniper Juniperus pingii – Ping juniper Juniperus procera – East African juniper Juniperus procumbens – Ibuki juniper Juniperus pseudosabina – Xinjiang juniper Juniperus recurva – Himalayan juniper Juniperus sabina – Savin juniper Juniperus saltuaria – Sichuan juniper Juniperus semiglobosa – Himalayan pencil juniper Juniperus seravschanica – Pashtun juniper Juniperus squamata – flaky juniper Juniperus thurifera – Spanish juniper Juniperus tibetica – Tibetan juniper
New World species
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