There are four academic theories regarding the origin of Ogham (which means language and is pronounced o’um, or och’um). The differing theories are unsurprising considering that it has similarities to ciphers in Germanic runes, Latin, and the Greek alphabet.
The first theory suggests that Ogham was first created as a cryptic alphabet designed by the Irish for religious or territorial reasons, that those with a knowledge of Latin could not read it. Second, that Ogham was invented by the first Christians in Ireland in a quest for uniqueness. The third, that it was invented in Wales in 400 CE to intertwine the Latin alphabet with the Irish language in response to the intermarriage of Romans and romanized Britons. The fourth theory is that Ogham was invented in Gaul around 600 BCE by Druids who created it as an oral language until it was finally put into writing.
Druids today use a particular method for communicating and remembering their tree knowledge, it consists of 20 strokes centred-on or branching-off a central line. It is similar in purpose, but separate in origin from the Nordic runes. The Ogham characters were inscribed on stones and probably on staves of wood
There are some five hundred surviving Ogham inscriptions throughout Britain and Ireland, located around south-eastern Ireland, Scotland, Orkney Isles, the Isle of Man, Pembrokeshire, and the border of Devon and Cornwall.
It is generally accepted in paganism and celtic spirituality that the twenty characters (called Fedha or Fews) form a secretive alphabet attributed to the ancient Druids to encode their wisdom. Less known, is that this modern interpretation of the Tree Ogham is largely based on the ideas of Robert Graves, following the publication of The White Goddess in 1948.
Modern Druid sources of information, for example: from Ireland, the 12th century Book of Leinster and the 14th century Book of Ballymote; from Scotland, transcribed from the oral tradition in the 17th century, The Scholar’s Primer.
For myself, as a Druid and a Botanist I find it curious that we continue to use Tree Ogham where only 15 of the 20 Fedha are trees, and one of those 15, the Fir, is not even native to the UK. Why assign only 14 native trees to the 20, given there are 31 species of trees native to the UK?
In 2003, the Irish writer Niall MacCoitir, referencing the 8th century Bretha Comaithchesa, and the 6th – 10th century Bríatharogaim, concluded that the Ogham alphabet is almost definitely a tree alphabet.
Alder : Alnus glutinosa
Ash : Fraxinus excelsior
Aspen : Populus trenula
Beech : Fagus sylvatica
Birch : Betula pendula
Blackthorn : Prunus spinosa
Wild Cherry : Prunus avium
Crab Apple : Malus sylvestris
Dogwood : Cornus sanguinea
Elder : Sambucus nigra
Wych Elm : Ulmus glabra (I)
Hawthorn : Crataegus monogyna (I)
Hazel : Corylus avellana (I)
Holly : Ilex aquifolium (I)
Hornbeam : Carpinus betulus
Juniper : Juniperus communis (I)
Common Lime : Tilia x europacea
Small-leaved Lime : Tilia cordata
Large-leaved Lime : Tilia platyphyllos
Field Maple : Acer campestre
English Oak : Quercus robur (I)
Sessile Oak : Quercus petraea (I)
Scots Pine : Pinus sylvestris (I)
Black Poplar : Populus nigra sub. Betuliflora
Rowan : Sorbus aucuparia (I)
Spindle : Euonymus europaeus
Sycamore : Acer pseudoplatanus *
Whitebeam : Sorbus aria (I)
Goat Willow : Salix caprea (I)
Grey Willow : Salix cinera sub. Oleifolia (I)
Yew : Taxus baccata (I)
I am not a linguist, so unfortunately I cannot suggest the necessary replacements. However, here is one suggestion:
Úr is often given as heather, a small low-growing shrub, meaning clay / moist. Elm is native, like heather, but it is a tree and is especially well-adapted to damp and cold conditions. In modern Irish the elm is referred to as crann úr. An argument for the replacement of heather with elm?
References and further reading:
Macalister, R. A. S. The Secret Languages of Ireland
McManus, D. Ogam: Archaizing, Orthography and the Authenticity of the Manuscript Key to the Alphabet
McManus, D. 1991 A Guide to Ogam
Swift, C. 1997 Ogam Stones and the Earliest Irish Christians
O’Dubhain, S. 2007 Druids, Ogham and Divination
Dillon, J. A Mythic History of Ogham
Carr-Gomm, P. & Richard, H. 2010 The Book of English Magic
Eastwood, L. A Re-evaluation Of The Ogham Tree List