Juniper

Common juniper
Juniperus communis

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Common juniper belongs to the genus Juniperus and is a member of the Cypress family (Cupressaceae).

Common juniper (Juniperus communis) is an evergreen tree growing to 6m and flowering May to June.

Lifespan: 100–200 years.

 

Characteristics

Often found as a low-growing, spreading shrub or small conical tree. Bark is grey-brown, peeling in strips with age. Leaves are alternating whorls of three on twigs. Leaves are needle-like, grey-green, small (10–15mm), tapering to a sharp, prickly point with broad white bands along the upper side.

Common juniper is dioecious, which means that male and female flowers grow on separate trees. Male flowers are small, yellow, globular and grow in leaf axils near the tips of twigs. Female flowers are small, green, globular, developing over 18 months into fleshy, dark purple, aromatic, berry-like cones; each containing three to six seeds. Common juniper can also reproduce vegetatively and is wind pollinated.

Juniper tree
Juniper leaves

Distribution

Native in the UK, across Europe and much of the northern hemisphere; common juniper has a vast geographic range.

Locally common on the calcareous soils and chalk down land of southern England and in the north and west of the UK it is found as a low-spreading shrub on moorland, in rocky areas or in old native pine woodland on wetter, peaty or acidic soils.

In the UK, common juniper is suffering from poor regeneration and its range is shrinking; it is therefore of conservation concern in this country. It is a priority species under the UK Biodiversity Action Plan and work is underway to restore and expand appropriate habitat and to establish the causes of decline. Common juniper is not threatened internationally due to its large geographic range.

There are a wide range of cultivated forms which are popular with gardeners.

Human value

Juniper timber has a warm sandy golden colour and an aromatic scent. It is popular even today for wood turnery and carving.

Aromatic wood can be used for smoking food and the berry-like cones are used to flavour gin and sauces for game.

Juniper also has medicinal properties. The berries produce an oil which can be used for respiratory and digestive problems.

Juniper flowers
Juniper berries

Wildlife value

In the UK, common juniper is an important component of a number of woodland and scrub communities; particularly those of chalk downs and native pine woodland.

It supports over 40 species of plant-eating insect including many moths such as the juniper carpet moth, juniper pug and the chestnut-coloured carpet moth.

Birds eat the berries and help in their dispersal; particularly the fieldfare, song thrush, mistle thrush and the ring ouzel in upland areas.

Common juniper provides low-level dense cover for nesting birds such as the goldcrest and firecrest and, in northern upland areas, the black grouse.

Management

Common juniper is a light-loving species and does well in open habitat; it is fairly intolerant of shade. It has a slow growth habit, typically growing just a few centimetres each year.

It can grow on both acid and alkaline soils provided they are well-drained to moist and at altitudes of over 1000m above sea level.

Seeds are very slow to germinate and require two winters of dormancy (18 months pre-treatment) before they begin to sprout. In the UK, propagation from seed is the preferred method as this maintains the genetic adaptability of our remaining population. For propagation and management guidelines visit Forest Research.

The browsing of foliage by deer, rabbits and domestic livestock may be playing a significant role in reduced regeneration.

Juniper may be affected by Phytophthora root rot (P. cinnamomi) and has recently been found to be susceptible to Phytophthora austrocedrae, a fungus-like organism which infects the plant via the roots and causes foliage to decline and eventually die. Juniper is also susceptible to rust fungus Gymnosporangium clavariiforme and G. cornutum, and it can suffer juniper blight Phomopsis juniperovora.

Juniper leaf

Illustrations © Reader’s Digest Association, Inc.
Photographs © Forestry Commission