4.2 Young trees

An approximate age for many young conifers can be determined by counting the whorls.   Some trees, including most conifers growing in the Pacific Northwest, have determinate height growth.  This means that they put on one “flush of growth” each year, and each year’s growth is determined by the previous year’s bud.  The terminal and lateral buds at the tips of the tree break bud, or “flush” in the spring (Figure 4.2).  The stems or “leaders” produced by these buds elongate until sometime in July, and then set new buds for the following spring.

illustration of a terminal buds bursting to allow new growth emerge

Figure 4.2. Terminal buds at the tip of the stem (left) flush and grow new branches and leaves each year (right). The center becomes the new leader, or main stem. The lateral or side buds become new lateral branches.

A tree increases in height by the length of the new leader growth produced by the terminal bud.  In addition, the lateral buds flush and produce a new whorl of branches at the base of the leader (old bud location) (Figure 4.3). This process is repeated every year.  Therefore, each whorl of branches and the stem growth immediately above it (up to the next whorl) represent one year of growth.

illustration showing one year's production of needles on a branch

Figure 4.3. An annual flush of growth represents one year, or one whorl of growth.

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4.2 Young trees by Joan DeYoung is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.