Ogham or Old Irish Ogam is an ancient Celtic/Irish tree alphabet/language of the Druids.

The term Druid means "The Wise person of the Oak." 

In the Welsh myths, a Druid was called dyn hysbys, which means 'Wizard.'

The Birch tree in Ogham called Beith was famed for being the pioneer tree by the Druids. they used birch to craft baby cradles as it was known for its powers of cleansing old to new,new beginnings and birth. Criminals use to cleansed of their sins by being 'birched.'

The mighty Oak tree called Duir in Ogham it represents the Druids as it is known for its strength, perseverance, continuity of the old traditions, longevity and endurance. Oaks have been known to live past five hundred years.

Druids would cut down Mistletoe that grew from the Oaks. According to Pliny the Elder (23 – 79 C.E.) Druids used their Golden Sickle to acquire the plant "Mistletoe was formally cut down on the sixth day of the New moon." Mistletoe was used as an all-purpose elixir crafted for healing even-though it was extremely toxic. It was used in their sacred Winter solstice rituals representing fertility, a woman would tie Mistletoe about her waist in order to make her fertile. Mistletoe used for good luck and fertility if you kissed your true love under it. In modern times Mistletoe is given out by druids for prosperity, fertility in the approaching New year.

The Druids would sit with their initiates under the mighty oak to teach their traditions, perform rituals or to sit quietly and reflect as pictured in their Sacred Grove below.

The Yew tree known as Ioho in Ogham represented reincarnation and infinity. Yew's have the power of rejuvenation and some are older than four hundred years old.

It appeared approx. 4th century C.E.as a script of 20 letters later 5 additional letters were included.

These Ogham letters were based on 25 woodland trees and plants to encode messages, divination and to account for ownership.

It was also used to serve as a memory tool by Bards who sang many of their tales and poems up until the 18th century.

 Ogham has been carved into wood, rocks and jewelry to used for their sacred rituals.

Source & References:

• O'Kelly, Michael J., Early Ireland, an Introduction to Irish Prehistory, p. 251, Cambridge University Press, 1989
• Ross, Anne (1972). Everyday Life of the Pagan Celts. London: Carousel. ISBN 0 552 54021 8
• Phillip Carr-Gomm, Richard Heygate,The Book of English Magic ISBN 978-1-4683-0069-7 copyright 20091.
• Featured Photo of Ogham alphabet by RedBubble.com
• Photo of Ogham sticks by A Walk Around Britain / FlickrPhoto of an Ogham inscription found in 1975 in Ratass Church, Tralee, County Kerry in Public Domain, Wikipedia
• Druid Sacred Grove in Wiki Commons.