There are a lot of different types of trees. A recent study found more than 60,000 different species of plants in the world, which is more than we think of as trees, like the palm tree, which is more closely related to grasses than oaks. My local lumberyard stocks wood from a tiny percentage of the world's trees, but still felt overwhelming. I wanted to make a garden bed. cedar is a good option due to its resistance to rot. Yes.

Asking a really stupid question is one way to get familiar with something. If they are good-natured, they will help and half the time you will find out that the question was not stupid at all. Eric Meier runs the Wood Database and has written several books about wood. I asked him what the hardest wood is.

We might think of strength in general, but that's not really what hard wood means. The USDA's Forest Products Laboratory puts out a Wood Handbook that has so many different measurements. Hardness is a thing. There is alsopressive strength parallel to grain, and the same for it.

There are many many ways that wood can fail, and experts test a lot of them.
There are many many ways that wood can fail, and experts test a lot of them. Geraint Rowland Photography/Getty Images

You can destroy a piece of wood in many different ways. You can bend it until it splinters. You can try to separate it from the other side. You can change it. You can stack heavy stuff on it and see how much weight it can take before it busts out the sides. You can perform repetitive tasks with it.

Some of the tests are a little silly, but they can all be done carefully and scientifically. You can measure impact bending by dropping a hammer onto a piece of wood.

Hardness is just one of the measures. It can be related to strength against bending or how much weight it can carry. It is specific about resistance to indentation. It isn't indicative of performance or durability. It is how much force it takes to make a difference.

Wood carving involves very carefully and artfully making wood fail.
Wood carving involves very carefully and artfully making wood fail. Kelly Cheng Travel Photography/Getty Images

Gabriel Janka was the creator of the Janka test, which is used to measure hardness. The American Society for Testing and Materials created standards for tests like Janka's.

You put a belt around a steel ball that is 0.44 inches in diameter. You press the ball into the wood. The Janka score is the amount of force it took to get the ball to the belt.

This test is much more complex than that. The wood has to be at a certain percentage. It has to be two inches thick, two inches wide, and six inches long. The test has to be done on each side of the block, for a total of six scores. The wood has to be free of knots. At 0.25 inches per minute, the ball should be pressed down. The main trunk of the tree is the source of the wood.

It makes sense that the Janka rating is correlated with the density of the wood. How useful is this test? How much does it take to slowly press a ball into wood? The Janka test is incredibly specific and not representative.

Hardness is a rather specific attribute: resistance to indentation.

Not all wood has the same water content. You are unlikely to be using completely knot-free samples for many types of wood. There are different parts of a tree and different parts of a trunk. The tree was cut down a long time ago.

The Janka score is an imperfect test, but it is ideal for flooring. Higher Janka scores correlate with more resistance to scratching and denting, and theoretically that could make for a more durable floor. You're unlikely to see much difference in the durability of your floors if you're above a certain level. The finish on the wood isn't the only thing that can cause scratching and dents in a hardwood floor.

Australian buloke is a very hard wood as well, sometimes called the hardest.
Australian buloke is a very hard wood as well, sometimes called the hardest. Courtesy Eric Meier/The Wood Database

If you look around, you'll see a tree called the Australian buloke listed as the hardest tree in the world. One source lists the Janka score at an incredible 5,060 lbs. of force, but another source found the score at half that, and the first source doesn't specify. Even if that one measurement was correct, Meier doesn't think it's representative of the species as a whole. Maybe it was a single hard piece of wood. It may have had a lower moisture content than the standard 12 percent. Who knows? There is a bit of doubt around that figure.

The hardest wood in the world is quebracho, with a Janka score of 4,570 lbs. In Argentina and Paraguay, it is found. The lignum-vitae, gidgee, snakewood, and camelthorn are on the list.

The hardest woods in the world have the same characteristics. They are usually from tropical or subtropical zones, and the closer you get to the equator, the harder the woods get. Some of the world's softest woods, such as pine and hemlock, grow well in cold climates. Balsa is an outlier. The wood is soft and grows in the tropics. Ultra-hard woods come from trees that are very slow-growing, long-lived and can be found in arid environments. Many of the trees never grow to the size of a shrub because of the lack of water.

The very hard quebracho tree has been extensively logged in its native range in South America.
The very hard quebracho tree has been extensively logged in its native range in South America. Christian Ostrosky/Alamy

The other big thing these trees have in common is that you should not buy them. There has been a lot of logging. In the last century or so, it was estimated that 85 percent of the trees in Argentina were cut down. African blackwood, or mpingo, has been overharvested as well, though it is listed only as near threatened by the IUCN.

The idea of sustainable lumber can work with specific species of tree. Pine, fir, and other fast-growing trees can be grown in a number of ways. Tropical hardwoods can't be replaced as quickly as other hardwoods. The biggest ethical certification label is the Forest Stewardship Council.

Forest managers can meet in order to get FSC certification, which allows them to charge more, though the standards are not always specific to each country. How much is being cut versus replanted, maintaining habitat for native species, protecting the rights of Indigenous communities, and many more are included in those standards. FSC doesn't inspect forests. Various auditing companies are used to do that. There are anywhere from 300 to 400 requirements that they are looking at, and this often results in auditors competing with each other for business, which has occasionally led to some fudged certifications.

It's kind of like the certified organic label in that it's not perfect, but it's important to tell consumers about the ethics of these products. There isn't a lot of research on this, but studies show mixed results when it comes to how well certified forests do in the long run. It is not as simple as I want it to be.

Pecan trees are a hard wood variety found in the United States.
Pecan trees are a hard wood variety found in the United States. Philip Gould/Getty Images

On the one hand, we need to create an economic model that keeps tropical forest as tropical forest. Some of the managers are small Indigenous communities that rely on the sale of a small number of tropical hardwood trees to survive. The land could be sold to an agricultural operation that wants to burn it down to make room for cattle.

"On the other hand, shipping is something we should be skeptical about." The orange was originally from Texas but is now found nationwide. In the Southeast, there are some hickory trees. There is a black locust from Appalachia. Ironwood is found in Southern California and Arizona. Most of the East Coast has flowering dogwood. Even though they are not always easy to find, several of these very hard hardwoods are available for purchase.

Don't go looking for the wood. It's enough to know that it's there.