The job of the saddle tree is to distribute the rider's weight over the horse's back, making it more efficient and comfortable for the horse. A tree consists of five basic parts - the two bars that run parallel, the fork that holds the bars together at the front, the cantle that holds the bars together in the back, and the horn. The cutout or tunnel underneath the fork is called the gullet. The open space created between the bars is called the gullet channel.
The bars of the saddle tree are the actual weight-bearing surface of the saddle. They're the part that's in contact with the horse. Well-fitting bars of a western saddle will apply only 3/4 lbs per square inch to the horse's back with a 150 lb rider up. In contrast, an English saddle, which has far less surface area, will apply about 1 3/4 lbs per square inch with the same rider up. This is what makes western saddles far easier on the horse despite their greater weight.
To distribute weight evenly, the entire length of the bars must be in even contact with the horse's back. The channel between the bars must be wide enough to keep pressure off the spine. And, the gullet height and width must be sufficient to keep pressure off the withers and shoulders.
How well a saddle tree will fit a horse's back is determined by the shape of the bars. There are three curves to the bars that will determine fit:
Rocker - Curve on the bottom of the tree
Twist - Curve from the front to back of each side of the tree
Flare - Curve at the front and back edges of the bars
Saddle trees are traditionally made of wood, which is how they came to be called "trees." Usually softer woods are chosen for their flexibility - Ponderosa Pine, Beachwood, Ash, Cottonwood, Douglas Fir. Once assembled, a covering is stretched wet over the tree and then allowed to dry and shrink, further strengthening the tree. Rawhide covering is the traditional material, with bullhide, the heaviest weight of rawhide, the top of the line. Lesser quality coverings include canvas, cheesecloth, and poorer quality hides. New fiberglass coatings are starting to win over some saddlemakers. After the covering is dry, a final coat of varnish is applied to seal the rawhide. The result is an exceptionally strong tree that still retains an amount of flexibility.
A bullhide-covered wood tree is considered by saddle makers to be the finest saddle tree construction. It is also the most expensive tree construction. With new synthetic materials appearing, saddle trees can now be built for about 25% of the cost of wood trees. As a result, today, the majority of manufactured saddles are built with synthetic trees.
Synthetic trees are built of plastic or fiberglass in a mold process and vary significantly in their quality. Ralide, is considered to be a suitably strong material, and the best of the synthetics. Synthetic trees have several other limitations. They aren't as flexible as wood trees. Since they're made with molds, there is little ability for any variation, resulting in cookie-cutter saddles. And, the synthetic materials also don't seem to be able to hold the nails and screws used in assembly as well as wood, making them less durable.
There is certainly a place for synthetic materials in saddle trees. They're appropriate for the casual rider who is very budget-minded. But, if you're looking to buy a quality saddle that will last a lifetime and handle whatever you may run into, you'll choose a bullhide-covered wood tree.
It's probably surprising to discover that there aren't any industry standards for saddle tree measurements and terminology. Different tree makers measure trees differently and even call the same trees by different names. So, you may think you're talking apples to apples, only to find that saddlemaker A's definition of a Wade tree is different from Saddlemaker B's definition. It doesn't really pay to try to become a saddle tree expert. It's a game you can't win. Better to seek out the advice of knowledgeable horsemen and saddle makers to guide you through the process.
At the risk of upsetting some folks, we warn you to be wary of gimmicks such as flexible trees. They can sound good in theory, but if they were the best way to go, the top custom saddle makers would be using them and you wouldn't find them on mainly lower cost saddles. They're really more of a response to the move towards synthetic trees on manufactured saddles which just don't flex and fit the way a wood tree does. If you have a high quality saddle with a high quality wood tree, you won't need a gimmick to fit your horse.
There are quite a number of different types of trees available. It's important to know that the name of a saddle tree refers to the style of the fork on that tree. The other parts - bars, cantle, horn, etc., can vary; if the fork's the same, it will have the same name. So you'll hear names such as Wade, or Bowman or Association and know that each of those names only identifies the tree as having a particular style of fork.
There are some general categories for bar types based on gullet width, but there is little agreement as to the widths and the names of the categories. It can be very frustrating. You'll even see names flip-flopped among the categories making for a tremendous amount of confusion when you're saddle shopping. At the risk of causing further confusion and argument, I'll share the following categories and gullet widths from Richard L. Sherer's "Horseman's Handbook of Western Saddles." Please keep in mind that there is no standardization of these measurements or names.
Arabian bars - gullet width: 6 1/4"-6 3/4" (has a flatter pitch than quarter horse bars)
Now where are we? Is your head spinning from information overload? Well, here's the good news. Saddle makers estimate that over 80% of today's horses have conformation that will comfortably fit them in either a standard semi-quarter horse or full-quarter horse tree. For most buyers, fit won't be an issue. The bigger challenge will be making sure you choose a saddle with a high quality tree. You should now be armed with enough information to ask the right questions. And when all else fails, price will be a very good indication of quality.
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