Definition and importance of a tree butt

The butt of a tree is its bottom portion and this basal portion of the trunk is distinctively different from a trees branches, roots, and upper trunk.   A trees  butt is above the roots but separated from the trunk which continues upward toward the terminal bud A trees butt is often referred to by loggers as the bottom log of a felled tree. The first cut  nearly always starts at the butt or base of the tree for the initial cut. It is the most valuable part of the tree when sold and converted to a wood product A tree butt is also important when tree disease is detected at or near ground level. Butt rot diseases  are serious concerns for tree owners and tree managers. A basal rot will inevitably weaken  the tree to the point where its support system is compromised  resulting in trunk failure and the eventual death of the tree. The butt of a tree is also its most valuable section to a timber grower. If there is a defect in the butt log which by definition is the first 16 feet of a tree trunk, the trees lumber grade is diminished considerably. Butt Rot and Effects on Trees Butt rot  is a serious disease of trees and all species are susceptible to a greater or lesser degree. Fungal pathogens are the primary causal agent of butt rot  and attack the moist, vulnerable and under-protected lower portion of a tree trunk where its largest diameter is recorded. A tree is most  vulnerable to rot where the bottom end of the trunk  stem  makes contact with the  soil. The tree butts location, when diseased, can  attack the roots as well causing a disease known as  root rot. These kinds of  infections are  likely to impair the transport properties of the  xylem  tissue found in the cambial region under the tree bark. Again, it also weakens the stem and makes the plant more vulnerable to toppling. Rot in the area of the tree butt can spread to the roots and/or  move up and into the tree compartment producing a roughly conical column of dead, rotted wood which increases in size proportional to a trees age and ability to compartmentalize and stop the spread. These wood-decay diseases can start as a root or butt disease but can  overlap as both root and  stem decays. Most are caused by Basidiomycota  or fungi. They may get in through wounds in the lower part of the tree or penetrate roots directly. Understanding a Butt Log and Its Quality The highest quality logs typically  come from the first or lowest section  called the butt log by timber harvesters. The butt log is where the best, highest quality wood veneer and lumber is found. Wood veneer (usually hardwood) that is sliced  or plywood (usually pine) that is rotary cut  command high prices. It should be noted that high-quality trees with butt log damage or disease will negatively affect what will be paid at the timber harvest time. Buyers of veneer and plywood quality wood will  require certain minimum log lengths depending on the mills operation and set up.   A  common minimum used in North America is  8 feet plus an extra 6 inches  for trim allowance. However, different veneer markets have different requirements for species, wood color and grain quality and can take logs as long as 11 feet plus 6 inches. Top grade veneer logs may have a 14-inch diameter minimum and extra prime grade  can only come from the first butt cut. What is Tree Butt Swell? All trees will have some taper but the most valuable timber tree will maintain a cylinder-like form extending up the trunk. Any extra expansion of  tree trunk butt above the normal stump flare is called butt swell and is normal in some tree species (especially trees on wet sites like cypress and tupelo gum). Sound wood within the butt swell can be used but only as non-construction materials including wood chips and specialty items. Timber cutters are  recommended to cut above the swell for construction logs. Butt swell is considered a defect for veneer logs.