If you look at the end of a log, you will notice there is always a lighter ring surrounding a darker inner ring. Sometimes this distinction is obvious, and other times it’s hard to distinguish the difference. The light outer ring is called the "sapwood", and this ring contains a tree’s living cells. All wood starts as sapwood. As a tree ages, its cells die and it becomes inactive and non-functional. This is the darker, inner core of the tree and is called the "heartwood".
The sapwood is the younger, softer outer portion of a tree that lies between the heartwood and the cambium (formative layer just under the bark). As comparatively new wood, sapwood is less durable and more permeable than heartwood.
While a floor purely of sapwood may be beautiful and smoother than heartwood, the softness and permeability of the sapwood makes it expand and contract easily, which can cause it to warp in certain conditions. This weakness manifests differently in various tree species. Some species have sapwood that is strong and durable, others have weak, soft sapwood that is not appropriate for wood floors.
Many times, sapwood is graded higher than heartwood because it is smoother and less prone to knots and blemishes. The highest-grade sapwood is virtually free of any imperfections. Coloration of sapwood ranges from white to light yellow tones.
Heartwood is the older, harder central portion of a tree. It usually contains deposits of various materials that frequently give it a darker color than sapwood. Heartwood is denser and more durable than sapwood and is found primarily in aged trees.
Heartwood makes a great wood floor because of its hardness and strength, and its resistance to many weather conditions. The hardness of heartwood, like sapwood, depends on the tree species and age of the tree.
Heartwood is usually graded lower than sapwood because it retains more imperfections and knottiness than sapwood. However, many people like the natural, rustic look of a heartwood floor. Some species, like heart pine, are graded higher than sapwood. Coloration of heartwood varies from deep reddish browns to yellows and ambers.
While many people choose either sapwood or heartwood, a very popular type ofhardwood flooring
comes from a mix of the two. The color differences between the two are less marked in some tree species, and more striking in others, like cherry, walnut, and hickory.
The mix may be graded. Grading assigns the wood a value, and this affects the price-- the higher the grade, the more expensive the wood. The grade depends on the different species’ valuation of heartwood and sapwood, and the amount of heartwood or sapwood in the wood. For example, different woods can be ordered and graded as no sapwood or no heartwood or mixed (heartwood and sapwood).
Staining and finishing a wood floor may be affected by the amounts of sapwood or heartwood in the floor because they accept and absorb stains and finishes differently.
Before deciding on a floor of heartwood, sapwood, or both, research different species of trees and their pros and cons, find out how a grade is assigned to the wood, and consult a knowledgeable wood floor installer. Armed with this information, you can buy the perfect floor safe and secure in the knowledge that it is exactly what you want.