The author is a research enthusiast. She studied botany and zoology as major subjects in her bachelor's program.
What Is a Hardwood Tree?
There are 60,000 different species of trees in the world. Hardwoods are woods from dicot trees. Hardwood is more complex in structure than softwood. It is different from softwood because of the presence of pores or vessels. As its name implies, the wood taken from hardwood trees is much harder and heavier.
Hardwoods are used in an extensive range of applications, including boat-making, tool-making, the production of musical instruments, and flooring. Read on to learn about "the Janka test" (a method used to assess trees' hardness) and the world's six hardest trees.
What Is the Janka Test?
This test was named after its creator, Gabriel Janka. Essentially, it is a test used to measure the hardness of a given wood. A 0.44-inch steel ball is embedded in a given wood. It measures the force required to embed a steel ball halfway into a sample of wood.
The Janka test is commonly used to measure the hardness of wood used for flooring. This test is also specifically enlisted to determine the suitability of the wood species for residential and commercial flooring.
World's 6 Hardest Trees at a Glance
|Tree Species||Janka hardness in lbf||Janka hardness in N|
2. Lignum Vitae
4. Camel Thorn Tree
5. African Blackwood
"Quebracho" is the common name of a very hard tree species. It is a Spanish word that means "ax breaker." The Janka hardness of the wood is 4,570 lbf (20,328 N). It grows almost 30 to 50 ft tall, and the wood color is a medium reddish brown with black streaks.
It is an important tree because of its tannins, which are extracted through the bark or heartwood. Some species are used in medicine because of their antifungal, antiviral, antimicrobial, and anti-inflammatory characteristics.
- White quebracho (Quebracho Blanco) is used to control the symptoms of asthma and the common cold.
- The astringent property of the white quebracho makes it suitable for wounds and burns.
- The bark of the tree is a tonic and stimulates the circulatory and genito-urinary systems.
- Tannins can be extracted from the quebracho tree, which is used for fine leather tanning. It enhanced the quality of leather goods, such as belts and garments, by making them more compact and tear-resistant with a nice touch.
- The wood is also used to prepare hardwood barbecue charcoal.
- Red quebracho (Schinopsis balansae) is used to add flavor to foods.
2. Lignum Vitae
This tree's common name "Lignum vitae" is Latin, which means "tree of life." The Janka hardness of this wood 4,390 lbf (19,528 N). It typically grows 20 to 30 feet tall and its color ranges from olive to dark green or black. The evergreen leaves are divided into leaflets and are leathery in texture.
The flowers are bright blue but gradually fade to white. The heart-shaped fruit is about 2 cm long. Because of its extremely high density, it has a propensity to skip over-top jointer cutters. It has a mild perfume-like odor.
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- It was used for treating coughs, gout, arthritis, and syphilis and was found in blood-purifying compounds.
- The resin from the tree is applied to teeth to treat toothaches.
- The tree possesses diaphoretic and alterative properties and has a stronger action.
- Guaiacum officinale is also known as "the tree of life" because of its historical use as medicine for people of the Caribbean.
- The resin is used for chewing gum and flavoring cake.
- Lignum vitae is the national tree of Jamaica and is widely planted in the streets.
- It is a compact and slow-growing species that can take decades to grow only 10 feet tall.
Lignum Vitae: The National Flower of Jamaica
Acacia cambagei is an endemic tree of Australia that can reach up to 12 m in height. The Janka hardness of this wood is 4,270 lbf (18,994 N). This moderately-growing tree can regenerate from suckers and basal shoots. The heartwood is reddish-brown or black.
The wood is very hard, termite-resistant, and very heavy. These characteristics make it suitable for fence posts. Flowers are pale to yellow, and flowering is sporadic from autumn into spring.
- The bark of the tree can be used for diarrhea, dysentery, and internal bleeding.
- It is also helpful for the treatment of wounds, hemorrhoids, and perspiring feet.
- It contains antiseptic properties and can be used as a mouthwash.
- The leaves, bark, and litter of gidgee produce an offensive odor, similar to gas or sewerage during humid weather, which accounts for the common name of "stinking gidgee."
- The tree can survive temperatures of less than -1°C. The young plant can be severely damaged at -1°C.
- The tree provides shelter to many animals, including king brown snakes, knife-footed frogs, black-breasted buzzards, and pied honeyeaters.
4. Camel Thorn Tree
Camel thorn (Vachellia erioloba or Acacia erioloba) is a slow-growing, very hard, and frost-resistant tree. The Janka hardness of this wood is 3,680 lbf (16,370 N). It can grow well in poor soil and harsh environments. The color of the bark is dark brown to black.
The flowers are ball-shaped and golden-yellow. The tree produces thick, ear-shaped pods as a fruit. Pods are a favorite meal for wild animals. Edible gum of good quality can be obtained from the stem.
- The dried powder of pods can be used to treat ear infections.
- The barkless root of the camelthorn tree can be used to cure tuberculosis.
- It is different from other acacias by the color of the foliage (which is blue-green), the black bark, and the pendant and broken branches.
- The pods are sometimes toxic to animals because of the presence of prussic acid.
- It is a very deep-rooted plant—descending its roots to a depth of approximately 45 meters.
- Its roots are used for making flutes.
- The shiny and eye-catching seeds of camelthorn are used in traditional necklaces.
- The wood is extremely hard and has been used for mine props, wagon building, and utensils.
5. African Blackwood
African blackwood (Dalbergia melanoxylon) is a flowering plant native to the dry regions of Africa. The Janka hardness of this wood is 3,670 lbf (16,325 N). It is the most valuable wood for the production of musical instruments.
It is widely distributed throughout Africa, including Tanzania, Nigeria, and Kenya. It is widely present in the Miombo woodlands of Africa and supports the livelihoods of approximately 100 million people. The average height of the tree is 4–7 meters.
- Decoction of roots can be used to prevent miscarriage and to treat diarrhea, abdominal pain, and gonorrhea.
- Leafs can be used for joint pains and to treat mouth and throat inflammation.
- It contains anti-bacterial and anti-fungal properties and is used for cleansing wounds.
- The smoke of the wood is inhaled to treat headaches and colds.
- The heartwood of African blackwood is the most expensive timber in the world because of its durability and resistance to biological deterioration.
- It is a slow-growing species, and it can take 70 to 100 years for a tree to attain timber size.
- It is a "near-threatened" species on the red list of threatened species.
- The main industrial use is the production of musical instruments like woodwinds. Because of its high density and neat texture, the instrument produces a beautiful tone.
Curupay is also known as “Cebil“ and “Patagonian rosewood.“ The Janka hardness of this wood is 3,630 lbf (16,147 N). It is mostly found in Argentina and Brazil. The color of the wood is pale to reddish-brown with black streaks.
It has a blunting effect on the cutter due to its high density. In Brazil, Curupay has been given a "high priority" conservation status.
- The bark of curupay is bitter and hemostatic. It is used to treat leucorrhoea, gonorrhea, and lung diseases.
- Gum is taken from the bark and used to treat respiratory conditions.
- Powdered seeds are used as a highly narcotic snuff.
- Cebil is used in traditional medicine to treat inflammation and respiratory problems, as well as in the industry for tanning leather.
- The leaves of the tree are toxic to cattle because of large quantities of cyanogenic glycosides capable of causing cyanic intoxication in cattle.
- A sugary drink is prepared from the bark of Anadenanthera colubrina.
- The wood is very hard and highly resistant to shocks. It is used for flooring, marine work, railroad crossties, tool handles, and turnery.
Further Info on the Janka Hardness Test
- African Blackwood | The Wood Database - Lumber Identification (Hardwood)
- Facts About Curupay | Woodworkers Source Blog
- Quebracho Supplement: Uses, Benefits, and Side Effects | MedicineNet
- Vachellia erioloba | PlantZAfrica
- Guaiacum Officinale | Useful Tropical Plants
- Camel Thorn Tree | Safari2Go
- Top Ten Hardest Woods | The Wood Database
- Lignum Vitae | The Wood Database - Lumber Identification (Hardwood)
- Facts About Acacia Erioloba | Plantzafrica
This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.
© 2022 EK Jadoon