Juniperus communis, Juniper
An evergreen European shrub with aromatic spiky foliage and berries with powerful antimicrobial and diuretic effects, giving a range of uses from insect repellent to treating cystitis.
scientific name Juniperus communis L.
family Cupressaceae
alternate names Savin, common juniper
parts used Fruit, leaf
Juniper bush aged about 12 years
Description
Juniper is an evergreen shrub or small tree with aromatic prickly needle-like leaves and fruits. It can grow to 9m by 4m at a slow rate. The flowers are dioecious and only one sex is found on a plant, so both male and female plants are needed for fruit to be produced. Pollinated by wind, the fruits take 2-3 years to ripen on the branches, turning from green to blue-black. This is a coniferous plant and the berries are actually composed of the fused fleshy scales of a cone.
Habitat
Juniperus is a native shrub of the northern temperate zone, ranging from Europe to Asia and North America. In southern England it is often found as a low-growing shrub on chalk downs and rocky areas, as well as in pine and birch woods in Scotland. According to the Woodland Trust, juniper populations in the UK are shrinking, and the species is a priority under the UK Biodiversity Action Plan.
Related plants
A dwarf form of juniper is J. communis subsp. nana mostly found in mountainous and coastal areas. There are many cultivated garden varieties of Juniper communis including spreading, creeping and dwarf forms. Eastern red cedar (J. virginiana), growing to 20m, is found in open woods of northern America and the fruit and leaves have similar properties.
Cultivation and harvest
Cultivation
Juniper is hardy to USDA zone 4 (UK zone 3). It prefers a slightly alkaline and well-drained soil but can grow in most soils including dry, poor soil or heavy, clay soil. The juniper shrub grows slowly but steadily in slightly acid and poorly drained soil at Holt Wood. It can grow in light shade or no shade. Juniper is tolerant of drought. Young growth can be damaged by late frosts. Prune in spring, removing dead or dying branches and thin out interior or crossing branches to enable more light to reach the plant.
Pests and diseases
Protection is needed for newly planted juniper which is very palatable to deer, rabbits, rodents and birds, ideally mesh covers which also insert 5cm into the soil. Mature juniper is more resistant to heavy grazing. Juniper resists honey fungus but may be infected by rust, and by Phytophthora root rot.
Propagation
The seed is slow to mature and only black berries should be picked.1 It is best sown as soon as it is ripe in a cold frame. Some might germinate in the following spring, though this can take up to four years. Stored seed requires a cold period followed by a warm period and then another cold spell, each of 2-3 months duration. Soaking the hard seed for 3-6 seconds in boiling water, or scarification, may help. The seedlings can be potted up into individual pots when they are large enough to handle. Grow on in pots until large enough, then plant out in early summer. Studies for the Forestry Commission suggest that cuttings are faster than seed; 10cm long hardwood cuttings should be taken in February or March from the tips of branches and inserted into a well-drained medium, misting for 12 weeks. Rooting should commence after 6-8 weeks, and misting can be gradually reduced so that at 16 weeks the plants can survive in a greenhouse and potted on.2
Harvesting
The fruits are usually harvested in the autumn when ripe. Leaves can be harvested at any time but are very prickly so wear thick gloves.
Juniper shoot
Therapeutic use
Traditional
Juniper has a long tradition of use in Europe and the berries are recognised as a traditional herbal product for minor urinary complaints, stomach upsets and flatulence.3 In northern America, juniper infusions were used as a tonic and for treating tuberculosis.4
Medicinal actions and uses
Diuretic, anti-inflammatory, antifungal, antimicrobial, anti-oxidant. The essential oil of juniper is strongly antibacterial,5 being rich in monoterpenes, although there can be variation between wild and cultivated species in the levels of different constituents.6
Clinical applications and research
Little clinical research has been carried out in relation to juniper leaves and berries although a study of the phenolic components indicates that the leaves have anti-oxidant and hepatoprotective potential.7 Another study argues that an extract of juniper berries has the potential for anticancer activity through suppressing cell growth.8 The effects of essential oils of juniper and other cypress family members against ticks and mosquitoes have been researched. It was found that all of the oils were repellent to ticks, and juniper leaf essential oil was the most repellent against the mosquito.9
Sample preparations and dosage
Pour 150-250ml of boiling water over 1-2g of dried berries. Infuse for 20 minutes in a covered container, and take 2-3 times daily. Tincture of leaves: 1-3ml three times daily. Although juniper can be taken internally for its diuretic effects, it is probably more useful externally as an antiseptic and insect repellent, as a wash or lotion. An infusion in oil can be made using the leaves and/or berries and this can be applied to the skin as an insect repellent.
Constituents and commerce
Key constituents
The leaves contain flavonoids. The essential oil of juniper berries contains monoterpenes (mostly α-pinene, also β-pinene, apigenin, sabinene, β-sitosterol, campesterol and limonene).
Commerce
Studies have shown that waste products of forestry activity in Poland, leaves and twigs of Juniperus species can contain significant amounts of podophyllotoxinins which could be used in cancer treatments.10
Safety
Safety during pregnancy and breastfeeding has not been established and use then is not recommended. Use with under 18-year-olds not recommended. Juniper is contraindicated in conditions where reduced fluid intake is recommended or in severe renal disease. Consult a professional clinical practitioner if used internally for more than two weeks.
Other uses
Culinary spice. Flavouring for gin. Making incense sticks. Antiseptic shampoo.
1 De la Bédoyère (2004) p69.
2 Broome A. (2003) Growing Juniper: Propagation and Establishment Practices, Edinburgh: Forestry Commission.
3 Bais S, Gill NS, Rana N, et al. (2014) A phytopharmacological review on a medicinal plant: Juniperus communis. Int Sch Res Notices 2014: 634723; Committee on Herbal Medicinal Products (HMPC). (2009) Community Herbal Monograph on Juniperus Communis L., Pseudo-fructus, London: European Medicines Agency.
4 Carpenter CD, O’Neill T, Picot N, et al. (2012) Anti-mycobacterial natural products from the Canadian medicinal plant Juniperus communis. J Ethnopharmacol 143: 695-700.
5 Pepeljnjak S, Kosalec I, Kalodera Z, et al. (2005) Antimicrobial activity of juniper berry essential oil (Juniperus communis L., Cupressaceae). Acta Pharm 55: 417-422.
6 Maurya AK, Devi R, Kumar A, et al. (2018) Chemical composition, cytotoxic and antibacterial activities of essential oils of cultivated clones of Juniperus communis and wild Juniperus species. Chem Biodivers 15: e1800183.
7 Ved A, Gupta A and Rawat AK. (2017) Anti-oxidant and hepatoprotective potential of phenol-rich fraction of Juniperus communis Linn. Leaves. Pharmacogn Mag 13: 108-113.
8 Tsai W-C, Tsai N-M, Chang K-F, et al. (2018) Juniperus communis extract exerts antitumor effects in human glioblastomas through blood-brain barrier. Cell Physiol Biochem 49: 2443-2462.
9 Carroll JF, Tabanca N, Kramer M, et al. (2011) Essential oils of Cupressus funebris, Juniperus communis, and J. chinensis (Cupressaceae) as repellents against ticks (Acari: Ixodidae) and mosquitoes (Diptera: Culicidae) and as toxicants against mosquitoes. J Vector Ecol 36: 258-268.
10 Och M, Och A, Cieśla Ł, et al. (2015) Study of cytotoxic activity, podophyllotoxin, and deoxypodophyllotoxin content in selected Juniperus species cultivated in Poland. Pharm Biol 53: 831-837.