50-55 species; see text.

Junipers are coniferous plants in the genus Juniperus of the cypress family Cupressaceae. There are about 50-55 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.

Junipers vary in size and shape from tall trees to 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 Common Juniper). 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.

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 being 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.

Classification

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 an obvious monophyletic group though.

• Juniperus sect. Juniperus: Needle-leaf junipers. The adult leaves are needle-like, in whorls of three, and jointed at the base (see below right).
  • Juniperus sect. Juniperus subsect. Juniperus: Cones with 3 separate seeds; needles with one stomatal band.
    • Juniperus communis - Common Juniper
      • Juniperus communis subsp. alpina - Alpine Juniper
    • Juniperus conferta - Shore Juniper
    • Juniperus rigida - Temple Juniper or Needle Juniper
  • Juniperus sect. Juniperus subsect. Oxycedrus: Cones with 3 separate seeds; needles with two stomatal bands.
    • Juniperus brevifolia - Azores Juniper
    • Juniperus cedrus - Canary Islands Juniper
    • Juniperus formosana - Chinese Prickly Juniper
    • Juniperus luchuensis - Ryukyu Juniper
    • Juniperus oxycedrus - Prickly Juniper or Cade
    • Juniperus macrocarpa (J. oxycedrus subsp. macrocarpa) - Large-berry Juniper
  • Juniperus sect. Juniperus subsect. Caryocedrus: Cones with 3 seeds fused together; needles with two stomatal bands.
    • Juniperus drupacea - Syrian Juniper

• Juniperus sect. Sabina: Scale-leaf junipers. The adult leaves are mostly scale-like, similar to those of cypresses, 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).
  • Provisionally, all the other junipers are included here, though they form a paraphyletic group.
    • Juniperus angosturana - Mexican One-seed Juniper
    • Juniperus ashei - Ashe Juniper
    • Juniperus barbadensis - West Indies Juniper
    • Juniperus bermudiana - Bermuda Juniper
    • Juniperus blancoi - Blanco's Juniper
    • Juniperus californica - California Juniper
    • Juniperus chinensis - Chinese Juniper
      • Juniperus chinensis var. sargentii - Sargent's Juniper
    • Juniperus coahuilensis - Coahuila Juniper
    • Juniperus comitana - Comitán Juniper
    • Juniperus convallium - Mekong Juniper
    • Juniperus deppeana - Alligator Juniper
    • Juniperus durangensis - Durango Juniper
    • Juniperus excelsa - Greek Juniper
    • Juniperus excelsa subsp. polycarpos - Persian Juniper
    • Juniperus flaccida - Mexican Weeping Juniper
    • Juniperus foetidissima - Stinking Juniper
    • Juniperus gamboana - Gamboa Juniper
    • Juniperus gaussenii - Gaussen's Juniper
    • Juniperus horizontalis - Creeping Juniper
    • Juniperus indica - Black Juniper
    • Juniperus jaliscana - Jalisco Juniper
    • Juniperus komarovii - Komarov's Juniper
    • Juniperus monosperma - One-seed Juniper
    • Juniperus monticola - Mountain Juniper
    • Juniperus occidentalis - Western Juniper
      • Juniperus occidentalis subsp. australis - Sierra Juniper
    • Juniperus osteosperma - Utah Juniper
    • Juniperus phoenicea - Phoenicean Juniper
    • Juniperus pinchotii - Pinchot Juniper
    • Juniperus procera - East African Juniper
    • Juniperus procumbens - Ibuki Juniper
    • Juniperus pseudosabina - Xinjiang Juniper
    • Juniperus recurva - Himalayan Juniper
      • Juniperus recurva var. coxii - Cox's Juniper
    • Juniperus sabina - Savin Juniper
      • Juniperus sabina var. davurica - Daurian Juniper
    • Juniperus saltillensis - Saltillo Juniper
    • Juniperus saltuaria - Sichuan Juniper
    • Juniperus scopulorum - Rocky Mountain Juniper
    • Juniperus semiglobosa - Russian Juniper
    • Juniperus squamata - Flaky Juniper
    • Juniperus standleyi - Standley's Juniper
    • Juniperus thurifera - Spanish Juniper
    • Juniperus tibetica - Tibetan Juniper
    • Juniperus virginiana - Eastern Juniper
      • Juniperus virginiana subsp. silicicola - Southern Juniper

Additional notes

The Rocky Mountain Juniper (J. scopulorum), One-seed Juniper (J. monosperma), Western Juniper (J. occidentalis), Utah Juniper (J. osteosperma) and California Juniper (J. californica) occur in the western United States. In the southwest United States there are four more species, including the Alligator Juniper (J. deppeana) with its thick bark checkered into scaly squares.

Many of the earliest prehistoric people lived in or near juniper forests which furnished them food, fuel, and wood for shelter or utensils. Many species (such as Chinese Juniper J. chinensis from East Asia) are extensively used in landscaping and horticulture.

Some junipers are sometimes misleadingly called cedars, the common name for species in the genus Cedrus, family Pinaceae.

Some junipers are susceptible to Gymnosporangium rust disease, and can be a serious problem for those growing Apples, the alternate host of the disease.

External links

• Gymnosperm Database - Juniperus
• Arboretum de Villardebelle Photos of cones and foliage of selected species