How to Count Double Butted Tree Rings

Tree rings not only tell how old a tree is, they help you discover weather patterns where they were growing. Wide rings mean lots of growth and good weather conditions while narrow rings mean lack of water or competition for nutrients.

Though most trees have only one set of rings, some trees contain two sets. These double-butted trees either have a split trunk or unsuccessfully tried to grow a split trunk, resulting in figure-eight shaped tree rings. However, you can count these rings just as easily as perfectly round ones with a little practice.

Things You'll Need

• Double-butted trunk cross section
• Ruler
• Red paint pen

Instructions

1. Examine your tree cross section. With a split trunk, count the larger arm of the split. Use a ruler to discover which split is wider. With an unsplit trunk featuring figure eight rings, count each figure eight as one ring.

2. Count tree rings from the outside to the inside, excluding the bark, matching light rings with dark so you're counting pairs. These two rings form in the same year. The lighter ring forms during fast spring growth, while the darker ring grows during slower summer growth. Dab a little red paint on each ring to help you keep track.

3. Note the number of rings you counted on a piece of paper. Study the rings to tell which ones are wider or narrower, discovering more about how the tree grew. Scars bisecting the rings may tell you how the tree split or why the rings are strangely shaped. Damage from animal scratches, lightning or another tree falling into yours may all cause long, jagged scars.

4. Count the tree rings in the smaller arm of a split tree to tell when the second arm was formed or began to grow. This may tell you that the sapling was harmed. On the other hand, some trees grow multiple trunks naturally.

References

• Arizona: Dendrochronology
• Idaho Forests: Tree Cookies
• Celebrating 200 Years: Be a Tree Ring Detective