Natural History of the Trees
of the Celtic Ogham

Please see the Wikipedia article for alternate views of the meaning of the names.

This list, taken from Clark (1995), identifies one, or sometimes several, species that corresponds to each letter of the ogham. I have compiled tidbits of the natural history that seem to relate to the mythic and divinatory meanings of the plants as set forth in Graves (1966) and Glass-Koentop (1991). I have noted which of these plants are cultivated in North America, although in my experience, few are readily available in nurseries. I have also pointed out those that have close relatives in North America. Many of the related species have similar appearance and similar natural history. Where no relatives are available, information about the natural history, especially habitat, growth form, and whether the plant is evergreen, should be useful in selecting correspondences among other native trees.

The trees are presented in ogham order, following the standard sequence of the Ogham alphabet. Each entry consists of the name of the ogham (in Irish or Gaeilge, following the standardized names, but see alternate names), and attempt to render the pronunciation for English speakers, the English name of the ogham, and a discussion of the actual tree species and their natural history. Scientific names follow Tutin et al. (1964), and for the most part represent the names currently used by most European botanists. Many of these plants will be found under other scientific names in the horticultural literature, and I hope to eventually include a synonymy.


(BEH), birch - The silver birch (Betula pendula Roth) is the most common tree birch in much of Europe. It grows up to 30 m (100 feet) high, but is more often found in spreading clumps on sandy soils. It is one of the first trees to colonize an area after a mature forest is cut; this is probably a large part of its symbolic connection with new beginnings. It is cultivated in North America, often under the name of weeping birch. The three trees in my front yard form root sprouts that would take over the bed where they are planted if I didn't cut them back. The common birch (B. pubescens Ehrh.) is almost as widespread as the silver birch, but grows primarily on acid or peaty soils. It can reach 20 m (65 feet) in height. Birches are members of the Birch family (Betulaceae).


(LWEESH), rowan - The rowan, or mountain ash (Sorbus aucuparia L.) is related to serviceberries. The red berries were historically used to lure birds into traps, and the specific epithet aucuparia comes from words meaning "to catch a bird". Birds are also responsible for dispersing the seeds. Rowans thrive in poor soils and colonize disturbed areas. In some parts of Europe they are most common around ancient settlements, either because of their weedy nature or because they were planted. Rowans flower in May. They grow to 15 m (50 feet) and are members of the Rose family (Rosaceae). They are cultivated in North America, especially in the northeast.


(FAIR-n), alder - The common alder (Alnus glutinosa (L.) Gaertner) is common along lowland rivers, where it grows with aspens, poplars, and willows. Like willows, alders sprout from stumps. This allows them to regenerate after heavy flooding. In protect sites they may grow to 20 m (65 feet) tall. Their leaves are more blunt-tipped than most North American alders, which look more like the grey alder (A. incana (L.) Moench). This species is more common in the mountains of Europe, and is not restricted to moist soils. Like ashes, European alders are not widely cultivated in North American (they are often sold as black alders), but several native species are. Alder wood is said to resist rotting when it is wet, and was the wood of choice for pilings in many regions. Alders are members of the Birch family (Betulaceae).


(SAHL), willow - Like North America, Europe is home to a large number of willow species (Tutin et al. list 63 different native European willows, from low shrubs to tall trees). Two common tree willows are the white willow (Salix alba L.) and the crack willow (Salix fragilis L.). The white willow is named for the whitish undersides of its leaves, and the crack willow for the propensity of its branches to "crack" off (probably another adaptation to flooding). Both species grow along with poplars and alders along lowland rivers. They can reach 25 m (80 feet) in height, and they both vigorously sprout from stumps. Other willow species are shrubs, including osiers (Salix purpurea L. and Salix viminalis L.) that grow along streams and eared willows (S. aurita L.) of acidic, boggy soils. The white willow and purple osier are sometimes grown in cultivation in North America. Willows are members of the Willow family (Salicaceae).


(NEE-uhn), ash - the common ash (Fraxinus excelsior L.) is a major tree of lowland forests in much of Europe, along with oaks and beeches. It grows to 40 m (130 feet) in open sites, with a broad crown reminiscent of American elm trees. Ash was and still is an important timber tree, and is a traditional material for the handle of a besom. The common ash is occasionally cultivated in North America, and similar native ash species are widely grown as street trees. Ashes are members of the Olive family (Oleaceae).


(OO-ah), hawthorn - Like willows, hawthorns have many species in Europe, and they are not always easy to tell apart. All are thorny shrubs in the Rose family (Rosaceae), and most have whitish or pinkish flowers. The common hawthorn (Crataegus monogyna Jacq.) and midland hawthorn (Crataegus laevigata (Poiret) DC.) are both widespread. They are common in abandoned fields and along the edges of forests. Both are cultivated in North America, as are several native and Asiatic hawthorns.


(DAH-r), oak - The oak of myth and legend is the common oak (Quercus robur L.). It is sometimes called the great oak, which is a translation of its Latin name (robur is the root of the English word "robust"). It grows with ash and beech in the lowland forests, and can reach a height of 45 m (150 feet) and age of 800 years. Along with ashes, oaks were heavily logged throughout recent millennia, so that the remaining giant oaks in many parts of Europe are but a remnant of forests past. Like most other central and northern European trees, common oaks are deciduous, losing their leaves before Samhain and growing new leaves in the spring so that the trees are fully clothed by Bealltaine. Common oaks are occasionally cultivated in North America, as are the similar native white oak, valley oak, and Oregon oak. Oaks are members of the Beech family (Fagaceae).


(CHIN-yuh), holly - The holly (Ilex aquifolium L.) is a shrub growing to 10 m (35 feet) in open woodlands and along clearings in forests. Hollies are evergreen, and stand out in winter among the bare branches of the deciduous forest trees that surround them. Hollies form red berries before Samhain which last until the birds finish eating them, often after Imbolc. The typical "holly leaf" is found on smaller plants, but toward the tops of taller plants the leaves have fewer spiny teeth. Hollies are members of the Holly family (Aquifoliaceae). The common holly is often cultivated in North America, as are hybrids between it and Asiatic holly species.

Graves (1966) and others are of the opinion that the original tinne was not the holly, but rather the holm oak, or holly oak (Quercus ilex L.). This is an evergreen oak of southern Europe that grows as a shrub, or as a tree to 25 m (80 feet). Like the holly, the holm oak has spiny-edged leaves on young growth. It does not have red berries, but it does have red leaf "galls" caused by the kermes scale insect; these are the source of natural scarlet dye. Holm oaks are occasionally cultivated in North America.


(CULL), hazel - The hazel (Corylus avellana L) is the source of hazelnuts. It forms a shrub up to 6 m (20 feet) tall, inhabiting open woodlands and scrubs, hedgerows, and the edges of forests. The filbert nut in North American groceries is Corylus maxima, a related species. The European hazelnut is cultivated in North America, primarily as an ornamental. Hazelnuts are in the Birch family (Betulaceae).


(KAIRT), apple - When most of us think of apples, we think of the domestic apple, but the ogham tree was most likely the European crabapple (Malus sylvestris Miller). This tree grows to 10 m (33 feet) in moist fertile soils in oak woodlands, and has been extensively cultivated. The fruits are small versions of the domestic apple, and also show the pentacle when cut across. Cultivated crabapples in North America are usually Asian species, but this species is a common rootstock for apple trees. Apples are in the Rose family (Rosaceae).


(MUHN, like "foot"), vine - The grape (Vitis vinifera L.) is a vine growing as long as 35 m (115 feet), in open woodlands and along the edges of forests, but most commonly seen today in cultivation, as the source of wine, grape juice, and the grape juice concentrate that is so widely used as a sweetener. European grapes are extensively cultivated in North America, especially in the southwest, and an industry and an agricultural discipline are devoted to their care and the production of wine. Grapes are in the Grape family (Vitaceae).


(GORT), ivy - Ivy (Hedera helix L.) is also a vine, growing to 30 m (100 feet) long in beech woods and around human habitations, where it is widely planted as a ground cover. Ivy produces greenish flowers before Samhain on short, vertical shrubby branches. The leaves of these flowering branches lack the characteristic lobes of the leaves of the rest of the plant. Like holly, ivy is evergreen, its dark green leaves striking in the bare forests of midwinter. Ivy is widely cultivated in North America. It is a member of the Ginseng family (Araliaceae).


(NYEH-dl), reed - The term "reed" is used with great imprecision in North America, but it is clear that the reed of the ogham is the common reed (Phragmites australis (Cav.) Trin. ex Steudel). This is a giant grass, with stems as high as 4 m (13 feet). It grows in marshy areas, where it often forms dense stands. Like most other grasses, the vertical stems live only a single year, dying in the autumn and being replaced with new green shoots in the spring. The dead stems rattle and whisper in late autumn winds. Common reed has spread as a weed throughout the world; in North America it is widespread in cooler climates. Common reed is in the Grass family (Poaceae, or Gramineae).


(STRAHF), blackthorn - The blackthorn (Prunus spinosa L.) is a relative of cherries and plums, and is the source of the sloe fruit. It is a thorny shrub growing to 4 m (13 feet), often forming thickets on south-facing slopes. The blue-black fruits are edible, but bitter until after the first frost. Blackthorns are seldom cultivated in North America. They are members of the Rose family (Rosaceae).


(RWEESH), elder - The common elder (Sambucus nigra L.) is a shrub growing to 10 m (33 feet) in damp clearings, along the edge of woods, and especially near habitations. Elders are grown for their blackish berries, which are used for preserves and wine. The leaf scars have the shape of a crescent moon. Elder branches have a broad spongy pith in their centers, much like the marrow of long bones, and an elder branch stripped of its bark is very bone-like. The red elder (S. racemosa L.) is a similar plant at higher elevations; it grows to 5 m (15 feet). Red elder extends its native range to northern North America, and it is cultivated along with other native species, but common elders are seldom seen in cultivation. Elders are in the Honeysuckle family (Caprifoliaceae).


(AHL-m), silver fir - The silver fir (Abies alba Miller) is one of the tallest trees native to Europe, sometimes exceeding 50 m (165 feet) tall. It is named for its silver gray bark. In its appearance (and in its current, and undoubtedly ancient, use) it is the quintessential Yule tree. It is not a tree of northern regions, however; it is commonest in central Europe and is replaced by other conifers in the north. Like most conifers, it is evergreen, and like other firs it produces cones that fall apart while they are still on the tree. Silver firs are seldom cultivated in North America, but several similar native species are. They are members of the Pine family (Pinaceae).


(UHN), furze - Furze, or gorse (Ulex europaeus L.), is a thorny shrub growing to 2 m (6 feet) tall. It grows in heaths, moors, pastures, and open woodlands. It produces bright yellow flowers around the time of the spring equinox. It is not often cultivated in North America, but is a serious weed in central California and some other areas. Furze is a member of the Pea family (Fabaceae, or Leguminosae).


(OOR), heather - Heather (Calluna vulgaris (L.) Hull) is a shrub growing to 2 m (6 feet). It is a major component of the vegetation type called "heath", the source of the term "heathen". It is evergreen, and produces bell-shaped pinkish flowers in the late summer. There are a number of other plants called "heath" or "heather" in the genera Erica, Phyllodoce, and Cassiope. These are relatives of Calluna, and are similar in appearance. Calluna is cultivated in North America, along with some of the other heaths and several Erica species from other parts of the world. Heather is a member of the Heath family (Ericaceae).


(EH-wah), poplar - The aspen (Populus tremula L.) grows to 20 m (65 feet) along rivers and as a pioneer species after fire or logging. It sprouts from the base and may form clumps or thickets. The black poplar (Populus nigra L.) reaches 30 m (100 feet) in sandy and gravely soil along rivers. The white poplar (Populus alba L.) is of similar size and habitat, but is more common in southern Europe. The white and black poplars are cultivated in North America (the "Lombardy poplar" is a form of black poplar), and several native poplars are similar in habitat and appearance. The North American aspen (P. tremuloides) is very similar to the European aspen. Poplars are members of the Willow family (Salicaceae).


(EE-wah), yew - The yew (Taxus baccata L.) is a slow-growing conifer, living as long as 1000 years and reaching 20 m (65 feet). It is much less common in recent times because of overharvesting (its hard, springy wood was the source of English longbows). The evergreen needles are very broad, and the seeds are produced in red, berry-like cones. Yews are toxic; one of the toxic compounds, taxol, is an effective treatment for some cancers. Yew is in the Yew family (Taxaceae).

Graves (1966) makes a case for an additional "blank" ogham, "the unhewn dolmen arch", which he assigns to the mistletoe, a plant for which there is abundant evidence of its ritual importance to the Celts. There are two common mistletoes in Europe, both of which live as parasites on trees. The common mistletoe (Viscum album L.) parasitizes many tree species, including oaks in the western part of its range. It forms white berries between Samhain and Yule. The yellow-berried mistletoe (Loranthus europaeus L.) does not extend to western Europe. It is found primarily on oaks. It is most likely the "golden bough", being more common in the eastern Mediterranean than the common mistletoe. The common mistletoe has been cultivated in North American for the Yule trade, and there are several native mistletoes in the genus Phoradendron. Mistletoes are in the Mistletoe family (Viscaceae).


  • Clark, Curtis. 1995. Natural history of the trees of the Celtic Ogham. Circle Network News 17(2):12-13 (Issue 56, Summer 1995). [This web page contains a revised version of the text of the article]
  • Editors of Sunset Books. 1988. Sunset Western Garden Book. Lane Publishing, Menlo Park, Ca.
  • Garms, Harry. 1967. The Natural History of Europe. Paul Hamlyn.
  • Glass-Koentop, Pattalee. 1991. Year of Moons, Season of Trees. Llewellyn Publications, St. Paul, Mn.
  • Graves, Robert. 1966. The White Goddess. 2nd, enlarged edition. Farrar, Straus and Giroux, New York.
  • Pokorný, Jaromír. 1974. A colour guide to familiar trees: leaves, bark, and fruit. (transl. Olga Kuthanová) Octopus Books, London.
  • Pokorný, Jaromír. 1975. A colour guide to familiar flowering shrubs. (transl. Olga Kuthanová) Octopus Books, London.
  • Tutin, T. G., V. H. Heywood, N. A. Burges, D. H. Valentine, S. M. Walters, and D. A. Webb. 1964. Flora Europaea. Cambridge University Press.
Return to top
Return to introduction to the ogham

Space for this page is provided by California State Polytechnic University, Pomona. Although it is intended to further the educational mission of the University, the opinions expressed here are those of Curtis Clark, and do not represent official policy of the University.

© 1996-2001 by Curtis Clark