The Irish Tree Alphabet (information compiled by Eric Rosenbloom)

Letter Name Tree Calendar Meaning
B
Beit, Beth, Beith, Bethe Birch January  
L
Luis Quicken, Rowan, Juniper, Mountain Ash January-February swarm
N
Nuin, Nion Ash February-March  
F
Fearn Alder March-April shield
S
Sail, Saille, Suil Willow April-May beam, eye, opening, sight
H
Uat, Uath Whitethorn, Hawthorn May-June
D
Dair, Duir Oak June rutting
T
Teitne, Tinne, Teine Furze, Holly July fire
C
Coll, Call, Calltuinn Hazel August  
M
Muin Vine September to piss, to teach
G
Gat, Gort, Gart Ivy October garden, vineyard, enclosed field, standing corn
P
Peit, Pethboc (Beith-bhog, soft B) Dwarf Elder November originally Ñ (Ngetal: Reed)
R
Ruir, Ruis Elder, Alder December  
 
A
Ailm Elm, Silver Fir, Palm Winter Solstice  
O
Oir, Onn Broom, Furze (conas, conasg) Spring Equinox border, strife
U
Ur Heath, Heather Summer Solstice new
E
Eadad, Eadha, Eubh Aspen, White Poplar Autumn Equinox death watch,
tingle in ear portending death
I
Ioda, Idho, Iubhar, Ibar Yew, Ivy Winter Solstice  

Notes.

There are 13 consonants and 5 vowels. Each consonant represents 28 days of the calendar, starting after the winter solstice. The Celtic feast days Oimelc, Beltane, Lunasa, and Samhain would occur, respectively, in the middle of Luis, the middle of Sail, the start of Muin, and the start of Peit.

The first variations listed above for name and tree are from Patrick Dinneen's An Irish-English Dictionary. The source for the calendar order is Robert Graves's The White Goddess. The normal order of the letters in the alphabet follows the Latin.

Correspondences to Hebrew should be noted: alef/ailm, beth/beit, he/eadha, yod/ioda, mem/muin, nun/nuin, 'ayin/onn, pe/peit, resh/ruis.

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