Myrica species

The wax myrtles or bayberries

Introduction

The bayberries (or wax myrtles) are deciduous and evergreen shrubs, and belong to the group of actinorhizal plants, that is temperate region plants which form associations with Frankia species of fungi in root nodules, which fix atmospheric nitrogen for the plant.

Leaves are alternate and often with resin glands, shaped like and resembling in aroma Mediterranean bay leaves (ie from Laurus nobilis); flowers are inconspicuous, without sepals and petals, in small dense catkins. All species are dioecious to a large extent (though not 100%), ie male and female flowers usually form on different plants. The fruit is a small round drupe, often with a waxy coating.

Although different species have some similar and some different uses, it should be borne in mind that these species are fairly similar and contain many of the same substances, hence all are likely (for example) to have medicinal uses etc.

Myrica californica

Cultivation

Most species prefer an open position in sun or partial shade (all grow well in the understorey of forests including conifer forests), and an acid or neutral well-drained soil. M.cerifera and M.californica prefer moist soils, and M.gale is well adapted to boggy sites. The evergreen species tolerate considerable shade. All tolerate strong winds and are suitable for using in windbreaks.

Plants of some species are fairly easy to grow from seed. The seeds have a coating of wax which must be removed before sowing - either gently rub the seeds between sheets of sandpaper, or soak them in hot water to melt the wax. Layering can also be used to propagate all species.

Root cuttings are the best way to propagate M.gale. Seed germination is unreliable for this specie, but can be encouraged by floating seeds on water at 5°C for several weeks, then sowing them in the light.

Young plants in the nursery may naturally become inoculated with Frankia species, and if they do then nodules will be seen on the roots. Plants can also be inoculated on planting by mixing a little soil from an established stand of the species or a relative in the planting hole.

All species are very tolerant of pruning and trimming.

Common uses for all species

• The wax which coats the small fruits of all species has been used mainly to make candles which are quite brittle, aromatic and don’t smoke when put out. Other uses for the wax include soaps, ointments, leather-polishes, etching, and medicinal mixtures. One litre of M.cerifera fruit yields 50 g of wax; the wax melts at 47-49°C (116-120°F), so is easily melted off fruits in hot water, and skimmed off the surface. It is harder and more brittle than beeswax.

• Bee plants. The flowers of all species are attractive to bees.

• Hedging. All species tolerate wind and maritime exposure, and can be used for an informal hedge.

• All are green manure plants, increasing the amounts of Nitrogen in the soil and making available significant amounts to other nearby plants. M.cerifera has been recorded as accumulating 120 Kg/Ha of nitrogen per year, making it one of the best temperate nitrogen-fixing shrubs. Dense stands of M.gale are estimated to fix at least 30 Kg/Ha/year. M.pensylvanica has been recorded as accumulating 16-32 Kg/Ha/year just from leaf litter; root turnover probably doubles this.

• Leaves of all species can be used as a spice / condiment.  They have a bay-like aroma.

Warning note: There is a report that some of the constituents of the wax may be carcinogenic, hence using the whole fruits in cooking (as a condiment) may not be advisable, although in small quantities there is probably little risk; the wax might also melt and mostly run off the cooked food, eg. roasted meat. Also, there are reports of M.gale having an abortifacient action; pregnant women should avoid taking any plant parts of any of these species internally.

M.californica

Californian bayberry, Californian wax myrtle. Found from California to Washington in the western USA.

Upright evergreen shrub, usually growing 2.5 m (8 ft) high, occasionally to 4-10 m (13-33 ft) high. Leaves are 5-10 cm (2-4”) long, dark green and glossy above, smooth or pubescent beneath; not as strongly scented as the other species. Catkins about 25 mm (1”) long in May-June; usually monoecious (both sexes on the same plant). Fruits are 4-6 mm (0.2”) across, deep purple with a white waxy coat. Hardy to zone 7 (-15°C) and hardy in most of Britain. Tolerates very acid and wet soils.

• Grey-brown and marron-purple dyes are obtained from the fruits, fresh or dried.

• The wood is heavy, very hard, strong, brittle, close grained.

• The bark and leaves have historically been used on occasion for gastrointestinal ailments. The most active chemical is apparently the glycoside myricinic acid.

Fruits of M. californica

M.cerifera 

Bayberry, Wax myrtle. SE North America, possibly naturalised in S.England.

Evergreen slender upright shrub or small tree, growing to 9-12 m (30-40 ft) high. Leaves are 3-7.5 cm (103”) long, deep green above, lighter below, both sides with tiny golden-yellow resin glands. Flowers in March-April; fruits are 2-3 mm across, greyish-white, waxy, in clusters of 2-6, and can hang on the plant for several years. Hardy to zone 6 (-20°C). ‘Myda’ is a large-fruited female form of low growth.

M.cerifera leaves

• Leaves and fruits are added to foods, eg soups, as a condiment (an agreeable bay substitute) (see note above). Leaves are also steeped to make a tea.

• Leaves show some antimalarial activity. They also repel fleas and moths.

• The bark, leaves and roots have all been used medicinally (the root bark was the ‘official’ drug, containing the triterpenes taraxerol, taraxerone and myricadiol). Being bitter and astringent, it stimulates the circulation, increases perspiration, and is antibacterial. It is still used for colds, flu, coughs and sore throats, irritable bowel syndrome, colitis, vaginal discharges, ulcers and sores.

• The root bark is used as a commercial flavour ingredient in some soft drinks in the UK.

• A blue dye is obtained from the fruits.

M.gale

Sweet gale, Bog myrtle. Northern temperate regions.

A common medium sized deciduous upright shrub, growing to 2.5 m (8 ft) high, but sometimes (from grazing pressure or poor sites) only to 50 cm (20”) or less. It spreads by rhizomes to produce thickets. Leaves 3-5 cm (1-2”) long, deep green and smooth above, somewhat pubescent beneath.

Although mostly dioecious, sometimes male and female flowers are formed on the same plant or even the same branch; flowers are brownish, cone-like catkins, 1.5 cm (0.6”) long in April-June, the females thicker than the males. Fruits are to 3 mm across, yellowish-brown.

Extremely hardy, to zone 1 (-45°C). Usually found on wet acid soils, also on neutral soils. The most striking feature of the plant is the pleasant smell of the volatile oil which is secreted from numerous glands on its leaves and catkins. The scent  resembles that of sage, but is more camphoraceous. It is readily grazed by hares and goats, also by sheep, cattle and deer.

Myrica gale

Sweet gale is a dominant species in several plant associations on open peatland, apparently growing best on ground strongly irrigated with mineral-rich water. It may thrive and achieve dominance on less fertile soils primarily because of its symbiotic association with nitrogen-fixing Frankia species in root nodules attached to the plant. Dense stands of M.gale are capable of fixing substantial amounts of nitrogen - 30 Kg/Ha/year has been estimated. It will also accept infection by many different Frankia strains from different species, including alders (Alnus), Elaeagnus, and sea buckthorn (Hippophae rhamnoides).

Though it grows in areas where water is close to the surface in summer and frequently flooded in winter, there is evidence that plant growth is in fact greatest in wet but well-aerated soil - plant growth is less on very wet soils and the dominance of sweet gale on such soils reflects superior tolerance rather than preference. Haemoglobin occurs in high concentrations in the root nodules of this species, which may be an adaption to growth in wet soils.

Catkins open in April or May and nodule activity begins in late May / early June when soil temperatures reach 8°C and leaves are beginning to unfold. New shoots grow from buds on the previous year’s woody stems and later in the season, from new aerial shoots arising from rhizomes. Leaf ageing and loss begins as shoots reach their final length and continues slowly through the summer while the same shoots are developing new leaves. During September or October, leaf production stops and leaf loss accelerates, leaving branches bare by November. At this stage, fruits are mature, nodule activity has ceased and the soil has been enriched by substantial amounts of leaf litter (which could benefit nearby trees, for example.)

The shrub has been harvested from the wild and utilised in various ways for centuries:

• The most widespread use in the past has been for flavouring beer. Evidence stretches from Roman and Viking sites for its use in brewing as a flavouring and preserving agent. ‘Gale beer’ in Yorkshire was considered very efficacious for slaking thirst. It is also used to flavour mead. The beer-preserving activity of M.gale is at least partly explained by the discovery of antibacterial flavonoids which are particularly active against gram-positive bacteria; these act in a similar way to the bitter compounds humulone and lupulone obtained from hops. The use of sweet gale in commercial beer making fell into disrepute 250 years ago because excessive consumption was believed to cause poisoning; but the present widespread consumption of M.gale flavoured drinks in Scandinavia (see below) is evidence against any severe toxic effects at the doses normally consumed.

• In Scandinavia, leaves are still gathered to flavour alcoholic drinks: in Denmark, Aalborg Pors Snaps is flavoured with an extract made by soaking freshly picked leaves in 35% aqueous alcohol; in Norway, dried and powdered leaves are sold to the public for flavouring spirits and home made beer.

• Other food uses still practised in Newfoundland include a tea made from the leaves; and the fruits are used as a condiment to season roast meat (see note above). the leaves have also been used as a food flavouring.  

• The roots have been used to produce a yellow dye for wool - used in the Scottish Highlands within the last 80 years. The stem tips also yield a yellow dye.

• The cultivar ‘Nanas’ is spreading and makes a good ground cover; it is very shade tolerant.

• Leaves yield a flavonoid and a volatile oil with antifungal activity against several species including Fusarium spp and Penicillium citrinum.

• There is plentiful historical evidence of the use of sweet gale as an insect (moth) and flea repellent in Scandinavian and British folklore, though the volatioil was never produced for this purpose. A strong decoction of the leaves can be used as a parasiticide to kill external body parasites (lice).

• The foliage has been used to repel midges in Scotland. Large scale production of M.gale is being considered after recent research on the Isle of Skye in Scotland demonstrated that the steam distilled volatile oil is an effective insect repellent (a 0.5% gel preparation of the oil repelled biting midges [Culicoides impunctatus] for up to 3 hours). The oil has also been shown to repel ants.

• The volatile oil is produced on catkins and fruits, as well as leaves, but the former are unlikely to  provide significant yield as they never exceed 0.73% of total dry weight. Following these experiments, a range of Myrica-based products is under development in the UK for which the source of oil is leaves harvested by hand in the Scottish highlands. Wild collection, although sustainable and allowing regrowth, is labour-intensive and unlikely to supply enough material if products are successful. Sustainable production depends on adequate regrowth after cutting - both wild and plantation sites are likely to suffer if too many leaves/twigs are harvested too rapidly.

• Sweet gale has the potential to become a valuable crop on land of low agricultural value.

• Recent pharmacological studies have focused on myrigalone B (MyB), a flavonoid extracted from the fruits. MyB is a potent antioxidant which may help to protect liver tissue from toxin-induced injury, and act as a preventative to atherosclerosis. A fresh extract of plant material in water has also demonstrated antiviral activity, which supports the Scandinavian folkloric use of M.gale extract to treat Herpes zoster.

Male catkins of bog myrtle  (source: Sten/Wikimedia)

Female flowers of bog myrtle (source: Hajotthu / Wikimedia)

M.heterophylla

Bayberry. Eastern N.America.

Very similar to M.cerifera; an evergreen shrub normally growing 3 m (10 ft) high, but occasionally a small tree to 12 m (40 ft) high. Leaves 4-7 cm (1½-3”) long, rounded at the apex. Fruits greyish-white, 3 mm across, with a heavy waxy coat. Hardy to zone 6 (-20°C). Has the same uses as M.cerifera.

M.pensylvanica

Northern bayberry. Eastern N.America, poss. naturalised in S.England.

Deciduous or semi-evergreen dense shrub to 2-3 m (6-10 ft) high. Tolerates very acid, saline and light sandy soils. Leaves 4-10 cm (1½-4”) long, pubescent on both sides, with glands beneath. Fruits are to 4 mm across, greyish-white, waxy, and persist long into winter. Very hardy, to zone 2 (-40°C). Closely related to M.cerifera, it may be a hardier northern form of it.

• Leaves and fruits used in cooking as a condiment (see note above).

• Leaves and root bark have been used medicinally.

• A green dye is obtained from the leaves.

• Widely used for erosion control in N.America.

• Bayberry essential oil, extracted from the aromatic leaves, is used to scent many products. It has a high eugenol content.

Myrica pensylvanica

Fruits of Northern bayberry

Myrica rubra

Red bayberry. Southern China and probably other parts of SE Asia.

Red bayberry, also called Chinese tree berry, Yangmei, Chinese strawberry tree, Chinese Bayberry, Japanese Bayberry,  Zhuhong, Zhuroing, Shanyangmei, Shumei (in Taiwan) or yamamomo (in Japan).  It is an important fruit and forest tree in China, with large and increasing areas cultivated (over 230,000 ha in 2003) to supply a large demand for the fruits.  As well as an important economic tree there, it has great ecological and social value too.

Myrica rubra (Syn. M.nagi) is a stone fruit with a  berry-like edible portion comprising fleshy segments.  The rich red colours and appealing flavour make this juicy fruit very popular with Chinese consumers.

Commercial cultivation of red bayberry has so far been mainly restricted to China, where most of the literature about it has been published.  Nevertheless there is great potential for growing it in other mild temperate and subtropical regions.

Red bayberry fruits (Photo courtesy of Zeping Yang

http://www.flickr.com/photos/zeping/)

Red bayberry is a cold tolerant evergreen fruit tree which can tolerate minimum winter temperatures of -9°C and grows and fruits well in temperate and subtropical zones with average annual temperatures of 14°C or more.  The species prefers a warm and humid climate with moderate to high rainfall (1000 mm annually).

It grows as a small to medium sized tree, often 5-10 m high in the wild in China and Japan, with smooth  bark (yellowish-green in young trees to grey-brown in mature trees) and a symmetrical rounded crown.  Branches are brittle and easily broken.

Fruits are usually deep reddish to dark purple (occasionally white, pink or black), flattish round, in cultivated varieties about 25-30 mm wide and little less long (or high), with a waxy coat.  They have a knobbly surface and look similar (though a little larger) to the fruits of the strawberry tree (Arbutus unedo) – hence one of the commercial fruit names, ‘Chinese arbutus’.  At the centre of the fruit is a single seed, about 8 mm in diameter (similar in size to a cherry stone).

In China, there are over 300 cultivars, most derived from chance seedlings, and most of which have been evaluated on agronomic characteristics and quality. 

The fruits of red bayberry are nutritious, succulent and aromatic, the flesh being juicy with a rich colour and an agreeable sub-acid (sweet-tart) taste resembling strawberry and cranberry. 

In China, many fruits are pressed to make juice which can be stored for longer or fermented. 

Due to its long lifespan, great economic value, low production costs and nitrogen-fixing ability, red bayberry is regarded as a “money making tree” and has been an important  economic source for people living in mountainous regions of China.  There, people prefer red bayberry to citrus, and beautiful packages of fresh fruits are used as precious gifts.  It has a strong social value in the life of Chinese people.

Apart from use as a fresh fruit, various products are made including juice (like a sweeter cranberry juice; available commercially outside of China where it is being marketed as bayberry juice and ‘yumberry’ juice), jam, fermented alcoholic beverages, brandy (soaked in the Chinese liquor ‘baijiu’), wine, candies, canned fruit, salted fruit and dried fruit.  It has an edible seed with 40% oil content of the kernel; the seed can be roasted or used for extraction of oils.

A water-soluble red pigment is extracted from the fruits and used as a food colouring.

Other uses of M. rubra include:

• The fruit, seed, bark, leaf and root of red bayberry are important components of traditional Chinese herbal medicine.  The fruit and leaf are used for treating congestion, coughs, digestive problems and diarrhoea; the bark is used for skin diseases, wounds and ulcers.  The seed kernels contain vitamin B₁₇ which can apparently inhibit or kill cancer cells.  In recent years, a number of pharmaceutically active compounds (flavonoids and polyphenols) have been identified from different parts of the plants.

• Soil conservation and regeneration  Red bayberry has extensive adaptability along with a nitrogen-fixing ability.  It is regarded as a “fertiliser generating tree” and widely used on poor soils and for soil conservation and reclamation projects, and to improve the organic matter content of soils.  It also has good fire resistance and is tolerant of heavy metal soil contamination.  It is often interplanted with forestry trees such as pines as a beneficial interplant; also as firebreak strips as the they are resistant to burning.  Up to 460 kg/ha of nitrogen can be fixed.

• Amenity  Red bayberry is a tall shapely tree which is resistant to pests and disease damage and tolerant of air pollution.  It is used as an ornamental tree in parks and along roadsides.  However, trees can make a mess of public streets when they drop fruit!

• Leaves and branches are used in floristry, especially in winter.

• The bark contains abundant tannin (10-27%) which is used as a dyeing material for dyeing cloth yellow and brown.