April 18, 2011

Bradford Pear

I apologize for the infrequent posts, but I’ve been doing a great deal of research lately.  I am still trying to wrap my head around the statistical information I am finding for each species.  What do these numbers truly mean to me the woodworker and how will they aid my understanding of a species that I have yet to work with?

One of the trees that I planned to discuss is the Bradford Pear (Pyrus calleryana).  I have a love/hate relationship with this tree.  It is one of the species that is hard to find concrete numbers on, and, for this reason, I was planning to delay posting about it even though it is a great follow up to the Redbud, but this week changed my plans.

My home state of Oklahoma is well known for its windiness, but Friday April 15, 2011, was ridiculous!  We had 40 mph sustained winds, with confirmed gusts to 70+ mph!!!  Are you beginning to see where this is headed?

We have (had) two straggly Pears along our driveway that we should have removed years ago, but they are blocking the view of a telephone pole.  Friday, half of one of the trees collided with our house.  That was the last straw.  I promptly felled the remainder of that tree (and its neighbor).  Twenty-four hours later the trees are completely gone.  The stumps have been ground.  The lawn has been repaired.  And the wood has been cut into turning blanks and sealed with Anchorseal. 

It was not how I had intended to spend my Friday and Saturday, and while the entire episode perfectly illustrates all that I hate about this species, I am quite excited by all of the Pear wood that I now have!

As I said, I have a love/hate relationship with Bradford Pear.  I love it once it is wood, but there are so many things that I hate about it as a tree.  I try to avoid being negative, but what follows is a short list of my grievances.

First off, let me say that I am using the term “Bradford” Pear quite loosely.  They are generically “Callery” Pears with many cultivars, which are supposed to be an improvement to the flowering pear.  “Bradford” just seems to be the most common varietal planted around here. 

This brings me to my first gripe.  This tree has been overplanted in the suburban landscape, at least where I live.  I don’t know if landscape architects were initially to blame or if the popularity coincided with the rise of the home improvement big box store, but these trees are everywhere.  Granted, they are quite striking with their profuse white flowers in the early spring, but the flowers are absolutely putrid smelling, with an odor similar to decaying flesh.  I have even heard that the nectar within these flowers is so thin and of such little value that honeybees will bypass the Bradford unless they have no other options.

My second gripe is that each of these flowers produces a small hard berry (presumably some sort of berry-shaped pear), but interestingly, I have never seen these consumed by birds or other wildlife.  They simply rot on the tree and drop off in the late fall, leaving behind a royal, slimy, nasty mess.

My third gripe is that the overall canopy shape is nearly identical from tree to tree.  They remind me of a bunch of lollipops jammed into the ground in Candyland.  They have very little character! 

My fourth gripe is that they are notoriously short lived, with a reported average lifespan of 25 years.  Huh…guess how many growth rings my trees had!!!  Bradfords must have been very popular in 1986, because there are many mature specimen around here that now look distressed. 

The fifth gripe may correlate with the fourth - the wood is brittle.  You can count on severe tree damage with any ice storm or wind event.  And that is where I stand today.  I will discuss this more when I post about the actual wood, but Pear has a very high specific gravity (0.73), which is comparable to Persimmon and only slightly less than Hedge (our hardest domestic hardwood).  This may be why the tree is considered brittle.  The wood may be too strong to bend and, instead, ruptures catastrophically.


The tree has simple alternate leaves of about 2 ½” with a waxy/shiny appearance and subtly serrated margins.

The bark is smooth and dark gray on young trees and twigs but develops to become neatly and narrowly furrowed.

The fall foliage ranges from orange to purple.

More about the wood of the Bradford in the next post. 

April 3, 2011

Redbud #2

The redbud may indeed be the poster child for Discovering Wood.  It is one of those woods that you have to kind of “luck into”.  You can’t go to the average lumber supplier and buy 110 board feet.  Even small owner-operated mills are rarely going to have Redbud lumber in any quantity, BUT it is a perfect example of the domestic exotics that we can harvest and mill in our own shops.

I “happened upon” a large redbud trunk early last summer when a storm decimated the over 100-year-old tree standing in my father-in-law’s farmyard.  The original owner of the property said that her grandfather specifically planted the Redbud sometime in the 1890s.  The center of the trunk had been ravaged by ants, termites, or some form of wood-eating insect over the years, and this is probably what ultimately made the trunk susceptible to wind damage.  The logs had already been bucked into two-foot lengths when I arrived, which precluded any long lumber, but what remained was perfect for home milling.  I retained some of the largest chunks and burls for turning blanks (along with any other chunky bits) and milled a fair bit into thin lumber. (More on my process in future posts).

The Numbers:

Specific Gravity
Density (#/cf)
Janka Hardness
“Shrinkage Ratio”

The reported specific gravity is 0.6363 (comparable to Ash) and density of 39.65 #/cubic foot (comparable to Walnut).  I’m trying to figure out exactly what these figures mean.  One source implies that specific gravity is the most important predictor of wood strength.  I thought it just determined if it would float (ala Salem witch trials).  I am equally unsure about the density figure, although I might expect it to relate to hardness or dent resistance.  If you have any insight, please let me know.  The other figure I came across is the Janka hardness scale (measured in pounds (or kilograms) of force required to press a roughly ½” diameter steel ball into the wood ¼”), although I have been unable to find a Janka number for Redbud.  If the Janka number correlates in any way with density, then we might assume that Redbud’s Janka is approximately 1000 (ie. softer than Red Oak but harder than Red Cedar) which is about how I would say that it behaves.

The other thing I have noticed is that Redbud has a tendency to split as it dries (even when the endgrain is sealed).  I have not had this issue with boards (although my boards are approx. ½” thick), but chunks left for turning are prone to split.  I am still working out what numbers would lend a predictability to this tendency.  On other species, I have seen numbers for the percentage of shrinkage from green to dry (both tangential and radial); perhaps the predictor is a ratio of these two numbers, as it would define shrinkage stresses.  I will investigate this further.  For now, let’s call this the “shrinkage ratio”.

Please bear with me as I compile and define some of these “technical” details.

Freshly milled boards.  The top board is partially planed.

On the practical side:

The most surprising thing about Redbud is the color. The wood is a mid to dark brown with streaks of red, yellow, and chocolate brown.  It is stunning.  There are surely growing condition and soil composition factors that determine how the wood ultimately looks.  I don’t know what those are, but I have seen an array of appearances in Redbud lumber from different sources.  I found the wood to be fairly fine-grained.  It is a little harder to carve than Black Walnut, but it does hold crisp detail.

"Redbud Leaves" 2010

On an interesting note, Hoadley mentions Redbud among a handful of other specieswhich fluoresce under ultraviolet light.  I bought a “blacklight” light bulb from Home Depot and had a lot of fun looking at different woods (I have several of the species); most fluoresce yellow and are really cool to look at but very difficult to photograph.  I can only imagine how it would look under a more powerful UV source, such as a woods lamp.
Redbud's yellow fluorescence under UV light.