I am sorry this is so late. When looking at the start date of the month I looked at Julys’ instead of Junes’.

From Ireland-Calling.com

Oak tree from Ireland

Oak – king of the forest

Known as king of the forest for its strength and longevity, the oak is most sacred to the Druids and the word Druid comes from the Celtic word for oak ‘Duir’.

The Oak was revered by many cultures throughout Europe, including the Greeks who associated the tree with the king of the gods Zeus, the Vikings who linked the oak to Thor, the Norse god of thunder and protector of mankind and the Celts with their own god of thunder Taranis relating to the tree.

Lightning strikes

Perhaps it is no coincidence that all these gods, with power over the weather, had an association with the oak tree since the oak is the tree most prone to lightning strikes and when struck will continue to thrive.

Druids believed that when the magical and sacred plant mistletoe grew on an oak tree it had been placed there during a lightning strike and was the most powerful of all the mistletoe.

The Druids had a sacred ceremony for removing mistletoe from the blessed oak using a golden sickle.

This would commence shortly after the new moon following the winter solstice, which may well be a reason why mistletoe is connected to Christmas today.

Inspiration for poets and bards

According to some accounts, one of the five magic trees of Ireland, The Tree of Mugna, was thought to be a mighty oak tree.

This tree was the inspiration for poets and bards, who, in some legends, overturned the tree themselves to save it the humiliation of being cut down by Christian monks as a symbol of paganism, as the other magic trees were.

Duir, Dair, D – Duir is the seventh letter of the ogham alphabet and the seventh month in the Celtic tree calendar.

The Oak is thought to be connected to the movements of the planet Mars. When Mars travels close to the Earth it is believed to stimulate the roots of the oak and when far away, the sun promotes upward growth making the oak one of the largest, most powerful trees in the forest.

Many animals rely on the oak tree for food and shelter and, in turn, regeneration of oak trees partly relies on the help of animals such as forgetful squirrels who bury their acorns as a winter food supply in Autumn, often not remembering where they put them.

Strong oak is used for building

The wood of the oak is very strong and was used in construction of houses and boats, furniture, fencing, barrels, anything where strength was of importance.

Its use in these areas continues today. The bark was used to tan leather and mixed with the leaves was used as an antiseptic tonic for treating infections of the digestive tract, rashes, wounds and burns. When times were hard, acorns were ground down to make bread in replacement of grain.

Oldest Oak tree in USA – Charleston, S.C.

From LearnReligions.com – Celtic Tree Months

Oak Moon

The oak tree has long been venerated by people of many cultures as a symbol of strength and power.

The Oak moon falls during a time when the trees are beginning to reach their full blooming stages. The mighty Oak is strong, powerful, and typically towering over all of its neighbors. The Oak King rules over the summer months, and this tree was sacred to the Druids. The Celts called this month Duir, which some scholars believe to mean “door”, the root word of “Druid.” The Oak is connected with spells for protection and strength, fertility, money and success, and good fortune. Carry an acorn in your pocket when you go to an interview or business meeting; it will be bring you good luck. If you catch a falling Oak leaf before it hits the ground, you’ll stay healthy the following year.