by Lorraine Schmid

I recently came across a couple of German forestry books by the author Erwin Thoma.  Herr Thoma is well respected for his forestry teachings, and is well known throughout Germany, particularly among private landowners who manage woodlots.

As German is my native language, I was eager to sift through and extract the essence of Thoma’s teachings in his book, Die geheime Sprache der Bäume: Die Wunder des Waldes für uns entschlüsselt (The Secret Language of the Trees: The wonders of the forest deciphered for us), and share them with those who work with this planting calendar.

When it comes to harvesting wood that will be used in construction—for buildings, sheds, houses, furniture and the like—Thoma promotes three basic principles. He claims that there is a faster and more even drying process compared to wood that was cut outside the recommended cutting periods. Also, there is less shifting of installed floor boards when the humidity changes from summer to winter. Another benefit is that cutting trees at the right time promotes pest resistance and fungal growth.

The first of Thoma’s principles relates to the time of year when the wood is cut. We all intuitively know that it’s best to cut trees in the winter. Did you know that trees have a different seasonal cycle compared to what we call winter?  Thoma claims that trees begin their winter season at the end of August when the sap has already started to move downwards.  While tree cutting can start at that time, the best time to cut logs for building purposes is from late November into January. As Thoma explains, in very cold regions, the sap flow in the tree stops at the end of August and begins again in the end of January or early to mid-February.

The second principle applies to the phases of the Moon. Thoma recommends that wood for building purposes should only be cut when the Moon is waning.  Waning occurs when the Moon moves from the Full Moon to the New Moon, and there is a decrease in the light reflected by the Moon. This makes sense because the sap moves down into the root systems during the waning Moon, so cutting at this time helps the wood dry better.
Thoma’s third principle relates to the signs of the Zodiac. He claims it is best to cut wood for building materials when the Moon is passing in front of an Earth constellation.

If you use all three of his principles as a guide, then the best time to cut wood for construction is during a waning Moon from November through January when the Moon is in Taurus, Virgo or Capricorn. According to the 2021 planting calendar, the optimum dates for cutting wood include December 9 to 11, 2020 and January 4 to 7, November 19 to 21 and December 26 to 29, 2021.

While there are other teachings around working with trees and the Moon, following Thoma’s three basic principles is an excellent first step in being in harmony with nature and the cosmos.