The Hedge Craft – Oak, also known as Quercus robur.
Oak, or Quercus robur, belongs to the beech family (Fagaceae). The parts most often used are the bark, leaves, acorns, and galls—sometimes called “oak apples,” which are formed by gall wasps on the leaves or acorns. Oak trees thrive in hedgerows, woods, and parkland, and can tolerate moist or even poor soil. They often interbreed with other oaks, such as sessile and downy oak, and are known for their slow growth.
Mature oaks can reach heights of 130 to 160 feet (40 to 50 meters) and live between 400 and 1,000 years. Their trunks can grow to about 30 feet (10 meters) in circumference. The leaves are lobed and ovoid, and the trunk is scaled grey-green with warty branches. Acorns are longer than those of American oaks and have a scaly “cap.” Male flowers appear as yellow-green catkins, while female flowers are less noticeable; both grow on the same tree. Because of their size, oaks create a unique greenish light in forests, opening the canopy to let sunlight in. Their crowns are irregular, with branches starting low on the trunk.
Oak galls are smooth, round, brown, and perforated. The knopper gall wasp (Andricus quercuscalicis) became common in the UK in the 1970s. These wasps lay eggs in developing acorns during early summer, turning the acorn into a ridged, woody structure for the larva. The gall starts yellow-green and sticky, then turns greyish-brown. The next generation of wasps forms galls on the male catkins of Turkey oak (Quercus cerris) the following year, alternating between the two tree species. This cycle is an example of natural sustainability.
Throughout history, oak has been valued for building homes, ships, and furniture. Its bark has been used for tanning leather and dyeing fabric, while acorns have served as food for pigs and, in times of scarcity, for people. Oak galls were once used to make ink, and the wood is prized for burning and making charcoal. Oak trees have provided shelter to historical figures such as Robin Hood and Charles II.
In Celtic tradition, oak is the second Ogham in the aicme of Huath and is one of the seven “nobles of the wood” in Brehon law. Oak forests once covered much of Europe. The tree is associated with thunder and lightning, and often survives lightning strikes. Its roots reach as deep as its branches reach high, symbolizing balance. Oak was the first tree species protected by law and is considered the chieftain tree of the Druids. The word “Druid” means “wisdom of the oak.”
In mythology, the Oak King and Holly King battle at each solstice, with the Oak King representing summer. Lightning-struck oaks were important in Druid and Celtic magic. The goddess Brighid’s original sanctuary in Kildare, Ireland, was a grove of oaks. In ancient Greece, the rustling of oak leaves was used for divination. Neolithic and Bronze Age woodhenges, such as Seahenge in Norfolk, were made of oak, and the tree was sometimes seen as the World Tree or axis mundi. Ancient oak trackways still exist in Britain. Oak was featured on old British coins, and King Arthur’s table at Winchester was made from a single oak trunk.
Chemically, oak contains tannins, tanning acids, and minerals. Medicinally, it is astringent, helping to tighten, dry, and tone tissue, and reduce excess discharge. It has been used for diarrhoea, dysentery, and inflammations of the eyes, mouth, throat, and digestive tract. Oak is also used for burns, sores, bleeding, coughs, and colds. It has anti-microbial and antiseptic properties, and can help with sweaty feet, chilblains, and anal tears (when used as a bark decoction in a bath). Acorn coffee may aid digestion, and oak is used homeopathically for alcoholism and to reduce fever. As a hair rinse, it can help with dandruff and hair loss. Compresses soaked in oak tea may shrink goitres and reduce glandular inflammation.
Oak bark decoction combined with nettle and yarrow makes a useful women’s tonic. Bruised oak leaves, especially when used with comfrey, can help heal bruises and sprains. The leaves are used for tea and tincture, the bark for decoction, and acorns can be ground and roasted as a coffee substitute. For internal use, 2 teaspoons of dried or 3 teaspoons of fresh leaf or bark per cup of boiled water can be taken up to three times a day. Tincture is typically used at 1 teaspoon three times daily. Leaf galls as tincture may help with severe diarrhoea and dysentery. Externally, decoction can be used for haemorrhoids, and bruised leaves for first aid on bruises, swelling, and sprains.
There are some cautions: oak may interact with morphine and could affect nicotine sensitivity.
Spiritually, oak is sacred to many deities. The Proto-Indo-European word for oak, “dorw,” became the word for “door.” Oak is seen as a doorway between worlds, with its high branches and deep roots. Celtic priests ate acorns to enhance divination, and oak was important in ancient Celtic funeral ceremonies. Acorns kept in the home or carried as charms are thought to bring good luck.
Oak teaches about strength and resilience, often surviving even after lightning strikes. For Druids, the oak symbolizes an ideal way of life: reaching toward the heavens while remaining deeply rooted in the earth. Water collected from oak’s nooks is considered to have empowering properties, especially in times of difficulty or loss of hope. Oak is believed to help develop inner sovereignty, kindness, compassion, and personal responsibility. It is seen as a spiritual ally, connecting people to other worlds and new perspectives.
Some oak trees in Britain are hundreds or even over a thousand years old. They can be powerful teachers, though some may seem indifferent to humanity. Respect for these ancient trees is important.
