What to know about Corylus avellana (hazel) before using it medicinally

Corylus avellana, commonly known as hazel, is a herb rich in health-promoting properties, including anti-inflammatory and antioxidant compounds, which have been shown to improve cardiovascular health and boost the immune system.

As a versatile and adaptable plant, hazel is often cultivated for its edible nuts, leaves, and bark, making it a popular choice among gardeners and horticulturists. From a botanical perspective, Corylus avellana belongs to the Betulaceae family and is a deciduous shrub or small tree, recognized by its distinctive leaf shape and catkin-bearing branches.

The hazel has a long history of use in traditional medicine, dating back to ancient Greece and Rome, where it was valued for its medicinal and spiritual properties.

This article explains the medicinal, horticultural, botanical, and historical aspects of Corylus avellana.

What are the medicinal properties of Corylus avellana?

Corylus avellana helps with cardiovascular health, inflammation, and antioxidant activity. It has been used to treat hypertension, atherosclerosis, and high cholesterol. The plant's extracts have also been shown to have anti-diabetic and anti-obesity effects.

The active constituents of Corylus avellana include flavonoids, phenolic acids, and terpenes, which contribute to its medicinal properties. Flavonoids such as quercetin and kaempferol have been identified as responsible for the plant's antioxidant and anti-inflammatory activities.

The most commonly used parts of the hazel plant for medicinal purposes are the leaves, bark, and nuts. The leaves and bark contain tannins, flavonoids, and phenolic acids, which are used to treat various ailments. The nuts are rich in vitamins, minerals, and fatty acids, making them a valuable source of nutrition.

Inappropriate use of Corylus avellana can lead to side effects such as gastrointestinal disturbances, allergic reactions, and interactions with certain medications. The plant's extracts can also cause uterine contractions and stimulate the uterus, making it contraindicated during pregnancy.

Precautions when using Corylus avellana medicinally include monitoring blood pressure, blood sugar levels, and liver function. It is also essential to consult with a healthcare professional before using the plant to treat any medical condition. Additionally, the plant should be used in moderation, and its extracts should be standardized to ensure efficacy and safety.

What are the horticulural aspects of Corylus avellana?

Corylus avellana grow best in full sun to partial shade, preferring moist, well-drained soil with a pH between 6.0 and 7.0. They can tolerate a range of soil types, but avoid waterlogging. Fertile soil promotes vigorous growth.

For optimal growth, plant Corylus avellana in autumn or early spring, avoiding extreme temperatures. Plant bare-root specimens, spacing them 4-8 meters apart. Avoid planting in areas with standing water or where water may collect. Mulching retains moisture and suppresses weeds.

Corylus avellana nuts are ready for harvest about 3-4 months after pollination. Gather nuts in late autumn or early winter when the husks are dry and rattle when touched. Leave some nuts on the tree to ensure continued reproduction. Harvest entire branches to encourage regrowth.

Pests affecting Corylus avellana include hazel dormouse, squirrels, and various aphids. Fungal diseases like canker and powdery mildew also pose threats. Regular pruning and good sanitation practices can help minimize damage. Monitor plants closely for signs of infestation or disease.

What are the botanical aspects of Corylus avellana?

Corylus avellana is a deciduous shrub or small tree with a conical crown, typically growing to 10-15m in height, with smooth grey bark and edible nuts.

Corylus avellana belongs to the Betulaceae family and is classified as follows: Kingdom: Plantae, Clade: Angiosperms, Clade: Eudicots, Clade: Rosids, Order: Fagales, Family: Betulaceae, Genus: Corylus, Species: C. avellana.

Corylus avellana has several variants, including 'Aurea', a golden-leaved cultivar, 'Lanuginosa', a woolly-leaved form, and 'Purpurea', a purple-leaved cultivar, as well as several cultivars with improved nut quality.

Corylus avellana is native to Europe and Western Asia, but has been naturalized in North America, and is also found in the Caucasus, Turkey, and Iran. It is often found in woodland edges and rocky areas.

Corylus avellana has a heterodichogamous reproductive strategy, meaning that male and female catkins are on separate plants, but on the same tree, in some cases. The nuts are borne in late summer and autumn, and are an important food source for birds, squirrels, and other small animals.

What are the historical aspects of Corylus avellana?

Corylus avellana is a plant with a long history of human interaction. It has been used as a source of food, fuel, and material for tools. Hazelnuts were a staple in ancient European diets, and hazelwood was used for making tools, such as axe handles.

In ancient mythologies, Corylus avellana was associated with fertility, protection, and wisdom. In Greek mythology, the hazelnut was said to be the gift of the goddess Demeter, who used it to grant fertility to the land. In Norse mythology, the hazel tree was said to have the power to grant wisdom.

Throughout history, Corylus avellana has been imbued with symbolic meanings. In Christianity, the hazel tree was seen as a symbol of faithfulness and loyalty. In Celtic cultures, the hazel tree was associated with poetry and wisdom. The hazel tree was also seen as a symbol of protection in ancient Celtic societies.

Corylus avellana has been mentioned in several historical texts. The Roman naturalist Pliny the Elder wrote about the hazelnut tree's medicinal properties in his book "Naturalis Historia". The Greek physician Dioscorides also wrote about the hazelnut tree's medicinal uses in his book "De Materia Medica". The Germanic tribes were known to have used the hazel tree for medicinal purposes.

Several historical artifacts feature Corylus avellana. The ancient Greeks and Romans used hazelwood to make tools, such as axe handles. The Celtic tribes used hazel wood to make spoons, combs, and other household items. Archaeologists have discovered ancient hazel nut processing equipment, such as stone mortars and pestles.