Make Botanical Tree Cookie Cross-Sections

Grand Fir Tree Cookie
Grand Fir Tree Cookie. Przykuta/Wikimedia Commons/CC BY 3.0

For those of you who don't know what a tree "cookie" is, a tree cookie is a sliced portion of a tree trunk or limb that can show each and every annual ring on a viewable plane. A tree cross-section disk or cookie can be one of the best botanical teaching aids to kids and adults on things happening in a tree and environmental effects on trees. It is especially effective visually in conifer specimens and more specifically pine.

Finding the Perfect Tree Cookie

Selecting a tree species that "shows well" is important when showing annual ring structure. Species that display visible dark annual rings are pines, spruces, cedar, and firs. Conifers used as Christmas trees are great for this if you use a real tree over the holiday. The wood is soft, easy to cut, and sand, and always displays nice rings.

Deciduous or broad-leaved trees can show nice rings by cutting their thick faster-growing branches (that also contain annual rings). Best trees for branch collections are oaks, ashes, maples, elms, cherry, and walnut. Trunk slices from these trees are often too large for display where rings are usually too tight and light to easily count.

The best tool for quickly felling a small tree is the standard curved large tooth pruning saw. A pruning saw will make quick work on a small tree's base or when cutting larger branches. At this point, you need to make a decision on whether to cut the cookies without drying or dry larger poles for cutting cross-sections later. These poles should be cut into four-foot segments with no end less than 2 inches in diameter.

The ideal slice size for quick production and use for a classroom is about the diameter of a soda can. Slice the logs into cookie segments between 1 to 2 inches thick. Use the same pruning saw or, for a fine surface, use a motor-driven saw such as a radial arm saw.

Drying Logs in a Kiln or Under Sheltered Storage

Kiln-drying short poles can be a more involved step to carry out but make for a much better tree slice specimen. A sawmill yard supervisor can dry your tree cookie logs in days using their lumber kiln. These logs will be sufficiently dry, feel much lighter and easier to cut with little to no chance of cracking. If you have time and a space you can set the logs in a dry, well-ventilated place for about a year.

Drying Cookies From Green Trees

Drying cookies cut from green trees is critical. If the sections are not dried properly, they will attract mold and fungus and lose bark. Store your cut cookies in a dry, well-ventilated surface under low humidity for three to ten days. Turn them over daily to allow both sides to dry. Placing them on a driveway on a sunny day also works. Cracking is a major problem if the cookie is not dried over sufficient time with adequate ventilation.

Getting the perfect “uncracked” cookie is a challenge, and the best way to prevent cracking is to cut cookies from a dried, not green, log or branch. Remember that the smaller the cookie, the less likely cracking will occur. Try cutting cookies from dried limbs, as the grain is often tighter in the limbs than in the main stem.

Curing Cookies Using PEG

Good preserving with less cracking results when you soak fresh-cut green cookies in polyethylene glycol (PEG). PEG draws the water out and replaces it with the PEG, which is a waxy material with excellent wood stabilizing properties. It also is not cheap and should be used primarily for your best specimens.

The disks from fresh-cut wood should be wrapped in plastic or immersed in water to keep in green condition until they can be treated. The PEG soaking time to obtain sufficient penetration against splitting and checking depends on the solution, the size, and thickness of the disks, and the species of wood. One month is usually sufficient soaking time and there is a drying time also associated.

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Your Citation
Nix, Steve. "Make Botanical Tree Cookie Cross-Sections." ThoughtCo, Apr. 5, 2023, Nix, Steve. (2023, April 5). Make Botanical Tree Cookie Cross-Sections. Retrieved from Nix, Steve. "Make Botanical Tree Cookie Cross-Sections." ThoughtCo. (accessed June 5, 2023).