Common juniper

Appearance

''Juniperus communis'' is a shrub or small coniferous evergreen tree, very variable and often a low spreading shrub, but occasionally reaching 10 m tall. It has needle-like leaves in whorls of three; the leaves are green, with a single white stomatal band on the inner surface. It is dioecious, with male and female cones on separate plants, which are wind pollinated.

The seed cones are berry-like, green ripening in 18 months to purple-black with a blue waxy coating; they are spherical, 4–12 mm diameter, and usually have three fused scales, each scale with a single seed. The seeds are dispersed when birds eat the cones, digesting the fleshy scales and passing the hard seeds in their droppings. The male cones are yellow, 2–3 mm long, and fall soon after shedding their pollen in March–April.

Naming

As to be expected from the wide range, ''J. communis'' is very variable, with several infraspecific taxa; delimitation between the taxa is still uncertain, with genetic data not matching morphological data well.
⤷ subsp. ''communis'' – Common juniper. Usually an erect shrub or small tree; leaves long, 8–20 mm; cones small, 5–8 mm, usually shorter than the leaves; found at low to moderate altitude in temperate climates.
⤷ *subsp. ''communis'' var. ''communis'' – Europe, most of northern Asia
⤷ *subsp. ''communis'' var. ''depressa'' Pursh – North America, Sierra Nevada in California
⤷ *subsp. ''communis'' var. ''hemisphaerica'' Parl. – Mediterranean mountains
⤷ *subsp. ''communis'' var. ''nipponica'' E.H.Wilson – Japan
⤷ subsp. ''alpina'' Čelak. – alpine juniper . Usually a prostrate ground-hugging shrub; leaves short, 3–8 mm; cones often larger, 7–12 mm, usually longer than the leaves; found in subarctic areas and high altitude alpine zones in temperate areas.
⤷ *subsp. ''alpina'' var. ''alpina'' – Greenland, Europe and Asia
⤷ *subsp. ''alpina'' var. ''megistocarpa'' Fernald & H.St.John – Eastern Canada
⤷ *subsp. ''alpina'' var. ''jackii'' Rehder – Western North America

Some botanists treat subsp. ''alpina'' at the lower rank of variety, in which case the correct name is ''Juniperus communis'' var. ''saxatilis'' Pallas, though the name ''Juniperus communis'' var. ''montana'' is also occasionally cited; others, primarily in eastern Europe and Russia, sometimes treat it as a distinct species ''J. sibirica'' Burgsd. .

''Juniperus communis'' is one of Ireland's longest established plants.