Black Locust

Naturally Decay Resistant Wood  Grown in Michigan

When early settlers moved into Michigan, they brought with them the knowledge of which fence posts last a long time in the ground.  This turned out to be wood from the Black Locust tree (Robinia Pseudoacacia).  Since Michigan was not the tree’s native range, folks moved to propagate it here.  Other benefits of Black Locust are erosion control, fast early growth, nitrogen fixation, as well as one of the hardest and most rot resistant woods growing in the US.  What we know now however, is that the Black Locust tree is a non-native invasive species that is hard to eradicate.  Once cut, the tree sends out vigorous runners & shoots.  When the conditions warrant, the Black Locust tends to crowd out native trees.  Well, when God gives you lemons, you make lemonade.  It may take years to fully eradicate this persnickety tree, if we choose to do so.  How can we best utilize this limited resource?   Well, we have a need to continue our agricultural and construction work in a manner that does the least damage to the environment.   This wood is grown in Michigan, so transportation costs are manageable.  Research at MSU and elsewhere suggest that some Black Locust posts have  been known to last as long as 100 years in the ground!  Chemical treatment is unnecessary, further ecological contamination is avoided.  The need to replace rotted posts is greatly reduced.

While relatively straight,  the Black Locust grows with some twists and quirks.  This wood is very heavy to handle.  The hardness of the wood requires the use of only very sharp tools and is recommended to pre-drill before fastening.

Our supplies vary from season to season.  Custom lengths are available.  While rare, the larger trees can be sawn for dimensional lumber.  Typically the tree sizes are suitable for poles.  Poles are sold unseasoned with the bark on and sight graded by us.   Shipping & handling can be arranged or you can pick up from one of our cutting sites throughout the region or at our yard in Benzie County.  Contact us for more information and price quotes.

Cutting & handling vary widely depending upon the site and our prices will reflect that.

Wood Characteristics Compared

IndexCedar (N. White)Red PineWhite OakBlack Locust
Modulus of Rupture5.38 kg/sq.mm8.8110.6813.63
Crushing Strength3,960 psi6,0707,44010,180
Static Bending FSPL7,700 psi7,00015,20012,800
Impact Strength12 inches263757
Modulus of Elasticity (10^6 psi).81.631.782.05
Hardness (Janka test)350 lbs56013601700
Shearing Strength850 psi121020002480
Specific Gravity0.320.460.680.69
Density; air dried24 #/cu.ft344648
Radial Shrinkage2.2%3.8%5.6%4.6%
Tangential Shrinkage4.9%7.2%10.5%7.2%
Rot resistanceFair(untreated) PoorHighVery High

Sources: U.S. Forest Products Laboratory, U.S. Forest Service, Gutenberg Project, Understanding Wood, A Craftsman’s Guide to Wood Technology, Bruce Hoadley