Have you ever heard of hardwood trees? You might think of trees like oak, which are known for their strong wood used in making furniture and campfires. But did you know that balsa, the super light wood used for model airplanes, is also considered a hardwood? It turns out that “hardwood” doesn’t always mean the wood is hard!
In English, you might expect “hardwood” to mean the wood is hard, right? Well, it used to be that way. A long time ago, when people were cutting down trees for building and fuel, they found trees like oak tougher to cut, so they called them “hardwoods.” Pine trees were easier to cut, so they got the name “softwoods.”
Most trees with hardwood have broad leaves and flowers. Scientists use these traits to group them into a category called “angiosperms.” So, “hardwood” (based on how tough the wood is) and “angiosperm” (based on genetics) became linked. On the other hand, “softwood” usually refers to trees with needle-like leaves and seeds that aren’t covered, which scientists classify as “gymnosperms.”
Generally, angiosperms (hardwoods) are harder than gymnosperms (softwoods). Softwoods evolved millions of years before hardwoods and have wood made up of long, thin cells running along the trunk. This means different softwoods have similar structures and hardness levels, measured by the Janka hardness scale. This scale shows how much force is needed to push a steel ball into the wood.
The hardness of softwoods can vary based on how fast the trees grow. Fast-growing trees have thinner cell walls, making the wood softer. Slow-growing trees have thicker cell walls, making the wood harder. For example, eastern red cedar is the hardest softwood, while northern white cedar is the softest.
Softwoods mainly rely on wind to spread their pollen, which is why they have less diversity in cell structure. Hardwoods, however, have evolved alongside animals that help pollinate their flowers and spread their seeds. This has allowed hardwoods to thrive in many environments, leading to a wide variety of species and cell structures.
Hardwoods can be as soft as balsa, which grows quickly and has very thin cell walls, or as hard as palo santo, which grows slowly and has tightly packed, thick-walled cells. Despite these differences, we still use the terms “softwood” and “hardwood” today, even though they don’t always describe the wood’s actual hardness!
Imagine you are a scientist classifying trees. Create a short skit with your classmates where you explain the difference between hardwoods and softwoods. Use props like leaves and seeds to show how scientists classify trees as angiosperms or gymnosperms. This will help you understand the characteristics that define each group.
Conduct a simple experiment to understand the Janka hardness scale. Use different types of wood samples, like balsa and oak, and test their hardness by pressing a small ball bearing into the wood. Record how much force is needed for each type and compare your results. This will give you a practical understanding of wood hardness.
Research the growth rates of different trees and how it affects their wood hardness. Create a chart showing the relationship between growth speed and cell wall thickness. Present your findings to the class, explaining why some woods are harder than others based on their growth rate.
Play a game that simulates the pollination process of hardwoods and softwoods. Use cards to represent different pollinators and tree species. The goal is to match pollinators with the correct tree type to show how diversity in hardwoods is achieved through animal pollination, unlike the wind pollination of softwoods.
Participate in a wood identification challenge where you examine various wood samples and determine if they are hardwoods or softwoods. Use clues like leaf shape, seed type, and cell structure to make your decision. This activity will help reinforce your understanding of tree classification and wood properties.
Sure! Here’s a sanitized version of the transcript:
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Do you know any hardwood trees? You’re probably thinking of a tree like oak, whose hardwood is used for making sturdy furniture and long-lasting campfires. But guess what other tree is considered a “hardwood”? Balsa – that lightweight wood that people use for making model airplanes. So, “hardwood” doesn’t necessarily mean that the wood is hard.
In English, doesn’t the “hard” have something to do with “hardness”? Well, it used to. Back in the medieval timber trade, while cutting trees for building material and fuel, loggers found trees like oak more difficult to cut, so they called them “hardwoods.” Pine trees, on the other hand, were comparatively easier to cut, so loggers called them “softwoods.”
Most trees with hardwood also happened to have broad leaves and flowers, traits eventually used by scientists to categorize trees into the taxonomic group known as “angiosperms.” So “hardwood” – a name based on physical properties – and “angiosperm” – a name based on genetics – became synonymous. The term “softwood” was mostly applied to trees with needle-like leaves and unencased seeds, traits used by taxonomists to categorize trees as “gymnosperms.”
These colloquial terms and taxonomic terms generally align: angiosperms (also known as hardwoods) are, on average, harder than gymnosperms (also known as softwoods). Softwoods evolved a few hundred million years before hardwoods did, and 90% of their wood consists of long, thin cells running parallel with the tree’s trunk. This means different softwoods have similar cellular structures and therefore are also of comparable hardness, according to the Janka hardness scale, which ranks trees from softest to hardest based on how much force it takes to drive a steel ball into their wood.
The differences in hardness that do exist among softwoods come mainly from the speed at which different species grow and mature: fast growth leads to thinner cell walls and less-dense, softer wood, while slow growth means thicker cell walls and denser, harder wood. Eastern red cedar – the hardest softwood – is only about three times as hard as northern white cedar – the softest softwood.
This relative lack of diversity in cell structure among softwood species is partly attributed to their pollination strategy: mainly, growing tall and letting the wind spread their pollen. Hardwoods, on the other hand, have co-evolved with the animals that pollinate their flowers and distribute their seeds. This has allowed hardwoods to spread rapidly in a variety of environments, leading to significant species diversity, including in the variety of their cellular structure.
Hardwoods range from the softest woods like balsa, which grows very quickly and has extremely thin cell walls, to the hardest woods like palo santo, which grows slowly and has tightly packed thick-walled cells, making it significantly harder than balsa! Knowing this, you’d think we would have retired the softwood/hardwood terminology by now, but some habits die hard.
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Hardwood – A type of wood that comes from deciduous trees, which are trees that lose their leaves annually. – Oak is a common type of hardwood used in furniture making because of its strength and durability.
Softwood – A type of wood that comes from coniferous trees, which usually have needles and cones. – Pine is a popular softwood used in construction because it is easy to work with and grows quickly.
Angiosperms – A group of plants that produce flowers and seeds enclosed within a fruit. – Roses and apple trees are examples of angiosperms because they produce flowers and fruits.
Gymnosperms – A group of plants that produce seeds that are not enclosed in a fruit, often found in cones. – Pine trees are gymnosperms because they produce seeds in cones rather than fruits.
Trees – Large plants with a trunk, branches, and leaves, which can live for many years. – Trees play a crucial role in the environment by providing oxygen and habitats for many species.
Pollen – Tiny grains produced by the male part of a flower or cone, which can fertilize the female part to produce seeds. – Bees help in the pollination process by carrying pollen from one flower to another.
Species – A group of living organisms that can interbreed and produce fertile offspring. – The giant panda is an endangered species that is native to China.
Diversity – The variety of different types of life found in a particular area or ecosystem. – The Amazon rainforest is known for its incredible biodiversity, hosting thousands of different species.
Environment – The surrounding conditions in which a plant, animal, or human lives and operates. – Protecting the environment is essential for maintaining the health of our planet and its inhabitants.
Genetics – The study of heredity and the variation of inherited characteristics in living organisms. – Genetics helps scientists understand how traits are passed from parents to offspring.
