Hardwood vs. Softwood

We’ve all heard the terms ‘hardwood’ and ‘softwood’, but what do they really mean? (Stop snickering, this turns out to be really interesting.) You may be surprised to learn that it really has little to do with the hardness or the denseness of the wood

Oaks are hardwoods (Jürgen Eissink) CC BY-SA 4.0

Pine trees are softwoods (yeowatzup) CC BY 2.0

While shopping to replace for my decades-old cutting board, I learned that there are some surprising differences between hardwoods and softwoods. Like most people, I thought I had it all figured out: hardwoods are hard and softwoods are soft, right? Well, not exactly. It ends up that hardwoods and softwoods are actually different types of plants.

Wood families

When it comes to hardwoods and softwoods, we are looking at two distinctly different ways of being a tree. Hardwoods are angiosperms, which means they are members of the flowering plants family, and they are dicots. Dicotyledons feature two seed leaves (cotyledons). Most hardwoods are deciduous, with flat leaves. Softwoods are in the gymnosperm family. Gymnosperms have bare seeds that are found on leaves, scales, or in cones, like pine trees. Most softwoods are evergreen, with needle-like or scale leaves. But this is where it gets weird. My orange trees are evergreen with flat leaves. Are they hardwood or softwood? How can I tell? It ends up, you need to look inside the tree to find out.

Rings & rays

Everyone has seen the rings of a tree that has been cut. Those rings can be used to determine the age of a tree, as well as the amount of rainfall and other environmental conditions each year. Each ring is made from the light colored growth that occurs early in the growing season and a dark layer of late season growth. One light ring plus one dark ring equals one year. Hardwoods tend to have similarly sized rings, while softwoods can have a lot more variation.

Vessels, pores & tracheids

Within every plant is some type of mechanism to move water and nutrients around. Hardwoods use vascular tissue, in the form of vessels and pores. Softwoods use structures called medullary rays and tracheids to produce sap and transport water and nutrients. Tracheids are chains of plant cells found in the xylem. The medullary rays are channels that that go from the center of the tree to the outer edge. Both types of trees have medullary rays, but softwoods rely on them exclusively, while hardwoods do not. Also, the medullary rays of softwoods are always straight and narrow. In hardwoods, the rays can be a variety of lengths and widths, depending on the species of tree, and erratically placed.

These trees support themselves differently, as well. Hardwoods use short fibers (right), while softwoods use the same longitudinal tracheids (left) they use to transport water and nutrients. The tracheids used by softwoods are much longer than the fibers used by hardwoods. (This is what makes softwoods so popular for paper-making.)

​Hardwood plant cells are vein-like tubes that connect the roots to the crown in an erratic arrangement with multiple paths, ensuring that the top of the tree will always be able to get water from the roots, regardless of disease or damage to one path.

Generally speaking, hardwood trees grow slower than softwoods. Softwood trees can be more of a fire hazard than the hardwoods. When selecting ornamental trees for your landscape, you will need to weigh the pros and cons of growth rate, flammability, leaf/needle drop mess, potential risks to nearby structures, and overall appearance.

Common softwood trees include redwood, spruce, yew, pine, Douglas fir and juniper. Popular hardwoods include beech, hickory, alder, maple, oak, teak, walnut, mahogany, and balsa. Yes, balsa.

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Note: Rather than cutting down my precious citrus trees, I looked it up: orange trees are hardwoods.