The Ogham and the Tree Calendar

The Ogham in plain words

Picture a standing stone with one straight edge. Along that edge someone has cut groups of short notches, one to five at a time, some to the left of the edge, some to the right, some straight across it and some on a slant. Each group is a letter. Read them, usually from the bottom up, and you have a name, usually the name of the person the stone remembers. That is the Ogham, and you can still find those stones in Ireland and in Wales, Scotland and Cornwall, the oldest from about the fourth century.

In its oldest form the Ogham has twenty letters, set out in four groups of five. Later scribes added a few more. What makes it interesting to us is that the medieval Irish scholars who wrote about the alphabet gave each letter a name, and a good many of those names are trees and plants. The scholars who wrote it up treated it as a tree alphabet, the way we teach children that A is for apple, and the tree names stuck.

I should say again what the Learning Celtic Tree Astrology page says at length: the alphabet is old and real, and the calendar that puts thirteen of its letters on the year is a twentieth century idea. Keep both halves of that in mind and the system will serve you well.

The thirteen letters this calendar uses

The tree calendar takes thirteen of the Ogham letters, the ones with the strongest tree names, and gives each one a month. In the spellings I use they are Beith for the Birch, Luis for the Rowan, Nion for the Ash, Fearn for the Alder, Saille for the Willow, Huath for the Hawthorn, Duir for the Oak, Tinne for the Holly, Coll for the Hazel, Muin for the Vine, Gort for the Ivy, Ngetal for the Reed and Ruis for the Elder.

Three of those would never pass as trees in a botany class. The Vine is a vine, the Ivy is a climber and the Reed is a tall grass. The calendar calls all thirteen trees and I have stopped apologising for it. Each tree page has a paragraph on what its letter meant, so I will not repeat that here.

Why thirteen months

A year is about 365 days. Divide it by about 28 and you get thirteen, with a day left over. Calendars that counted by the Moon often ran to thirteen months for that reason, and the tree calendar borrows the shape. Its months are called lunar months because thirteen of them fill a year, and that is the whole of it. They do not follow the Moon's phases. Your tree month does not start on a New Moon, and the Full Moon can fall anywhere in it. The Moon page in the Western Astrology section is where the real Moon lives.

Thirteen also happens to be a good number of characters. Twelve signs is familiar. Thirteen trees is just unfamiliar enough to make you look again.

The dates

Here is the whole year, and these are the dates my calculator uses.

The Birch, Beith, runs from 24 December to 20 January. The Rowan, Luis, from 21 January to 17 February. The Ash, Nion, from 18 February to 17 March. The Alder, Fearn, from 18 March to 14 April. The Willow, Saille, from 15 April to 12 May. The Hawthorn, Huath, from 13 May to 9 June. The Oak, Duir, from 10 June to 7 July. The Holly, Tinne, from 8 July to 4 August. The Hazel, Coll, from 5 August to 1 September. The Vine, Muin, from 2 September to 29 September. The Ivy, Gort, from 30 September to 27 October. The Reed, Ngetal, from 28 October to 24 November. The Elder, Ruis, from 25 November to 23 December.

The dates are the same every year. There is no leap day shift, no adjustment for where you were born and no birth time to find. Every day of the year belongs to one tree and only one. If you were born on 29 February, you are an Ash like everyone else born in the back half of February, and you can enjoy having the rarest birthday in the Ash month.

Working it out

There is no working out, which is the pleasure of this system. Find your birthday in the list above and read off the tree.

Sarah, born on 14 March, falls between 18 February and 17 March, so she is an Ash. Emma, born on 6 August, falls between 5 August and 1 September, so she is a Hazel. Someone born on 30 September is an Ivy, the very first day of the Ivy month, because the Vine ended the day before. Someone born on 23 December is an Elder, the last day of the year, and someone born on 24 December is a Birch, the first day of the next.

If you sit on a boundary

People ask me what to do when their birthday is the last day of one tree or the first day of the next. The answer is nothing.

In Western astrology a boundary date is a real question, because the Sun changes sign at a different moment each year and the answer depends on the year and the place. Here the dates are fixed by the calendar itself. If you were born on 23 December you are an Elder. If you were born on 24 December you are a Birch. There is no cusp and no chart to check.

That said, I would read both pages if you are within a day or two of a boundary. You are still the tree your date gives you, and the two pictures sit next to each other for a reason. The Elder closes what the Birch is about to open, and a person born on the hinge often knows something about both. Read it as a neighbour.

What comes next

Your tree is coming to Find Your Numbers and Signs, where it will appear beside your numbers and your signs, so you will see it in one place with everything else. Until then the list above is all you need.

Once you have your tree, go to The Trees and read your page. Then come back and read the page for your letter's neighbours. You will start to see the year as a row of trees, each handing the light to the next, and that is a good way to see it.

If you would like your own chart read, my readings are here.

Related pages
The Chinese Calendar and the New Year · The Tzolkin Calendar · The Elder Futhark