A Tree and Its Trunk page 4

At some time during your life you must have seen annual (growth) rings, and you know that each growth ring represents a year. What makes these rings? An annual ring is one year's worth of xylem growth. In most trees the xylem cells formed in the spring are larger than those formed later in the summer. The difference in size results in what appears as a ring. In some species such as oak and ash the spring xylem is so wide you can actually see them with the naked eye resulting in a very clear ring.

FORSite>Contents>How a Tree Grows>A Tree and Its Trunk (4 of 5)
*A Tree and Its Trunk*
At some time during your life you must have seen annual (growth) rings, and you know that each growth ring represents a year. What makes these rings? An annual ring is one year's worth of xylem growth. In most trees the xylem cells formed in the spring are larger than those formed later in the summer. The difference in size results in what appears as a ring. In some species such as oak and ash the spring xylem is so wide you can actually see them with the naked eye resulting in a very clear ring.