When holly goes pathological
Only fungus and injury cause color change in normally white holly. 1998.
by Professor Gene Wengert
Recently I called a sawmill in PA about the price of KD holly. One of the selling points was that it was all white, no green. It has been rare for me to mill holly with green, however I frequently find gray spots and streaks. It is rare for me to saw any that is all white. What causes the gray, heart wood? What causes the green?
The normal color of holly is white--both sapwood and heartwood. However, bluish (or perhaps greenish?) steaks will be seen and would be classified as mineral, which is not a grading defect according to the NHLA rules.
It would be expected, however, if the tree were injured, it would close off the injured area (this is the way a tree protects itself from fungal, bacterial, and other invaders, as it doesn't have antibodies like we do). The closed off area is often called pathological heartwood (because it is like heartwood, but the heartwood is not caused by aging but by a pathogen) and the heartwood so formed is grayish in color (perhaps because of the presence of fungi that discolor the area?).
Hard maple is a species that is also well known for its ability to encapsulate the wounded area.
Professor Gene Wengert is Extension Specialist in Wood Processing at the Department of Forestry, University of Wisconsin-Madison.
Click on Wood Doctor Archives to peruse past answers.
If you would like to obtain a copy of "The Wood Doctor's Rx", visit the Wood Education and Resource Center Web site for more information.
Would you like to add information to this article?
Interested in writing or submitting an article?
Have a question about this article?
Have you reviewed the related Knowledge Base areas below?
KnowledgeBase: Lumber & Plywood: Buying
KnowledgeBase: Primary Processing: Lumber Grading
KnowledgeBase: Wood Engineering: Wood Properties
KnowledgeBase: Knowledge Base
All rights reserved. No part of this publication may be reproduced in
any manner without permission of the Editor.
Review WOODWEB's Copyright Policy.
The editors, writers, and staff at WOODWEB try to promote safe practices.
What is safe for one woodworker under certain conditions may not be safe
for others in different circumstances. Readers should undertake the use
of materials and methods discussed at WOODWEB after considerate evaluation,
and at their own risk.
335 Bedell Road
Montrose, PA 18801
Copyright © 1996-2017 - WOODWEB ® Inc.