An adjustable tree is a saddle tree — the internal framework that gives a saddle its shape and structure — that can be altered in width to fit different horses or to accommodate changes in a horse’s body condition over time. The tree is the foundation of any saddle: it sits across the horse’s back, distributes the rider’s weight, and determines whether the saddle fits correctly or causes discomfort and injury. In a traditional saddle with a fixed tree, the width is set at manufacture and cannot be changed. An adjustable tree removes that limitation.
For horse owners who ride different horses, or whose horse’s topline and muscle condition changes significantly between seasons, a saddle with an adjustable tree can be a practical and cost-effective solution compared to buying a new saddle every time the horse’s shape changes.
How an Adjustable Tree Works
The most common adjustable tree design uses a gullet plate system. The gullet plate is a metal or composite component that bridges the front arch of the saddle tree, and it is available in different widths — typically ranging from narrow through to extra-wide. Changing the gullet plate widens or narrows the angle of the tree’s front arch, altering where the saddle sits in relation to the horse’s withers and shoulders. This can usually be done at home with a screwdriver, though it is recommended to have the adjustment checked by a qualified saddle fitter.
Other designs use a more flexible tree construction — often incorporating a sprung or semi-rigid central frame — that distributes weight dynamically as the horse moves. These are sometimes described as “flexible tree” saddles rather than strictly adjustable, and they suit a wider range of horses without specific manual adjustment.
Premium adjustable systems, such as those with micro-adjustable screw mechanisms or those requiring a saddle fitter’s tool to alter, offer finer control over the fit but cannot be adjusted independently by the rider.
Benefits of an Adjustable Tree Saddle
The primary benefit is versatility. A horse’s back changes considerably throughout the year — typically carrying more muscle and condition in summer work and losing topline through winter rest. A horse’s shape also changes significantly between the ages of three and seven as the musculature matures. An adjustable tree can accommodate these fluctuations without requiring a new saddle each time.
For riders who compete on multiple horses, or who are in the process of bringing on a young horse whose body is still developing, an adjustable saddle removes the need to own several saddles. This is particularly relevant given the significant cost of quality custom-fitted saddles.
Limitations and Considerations
An adjustable tree is not a substitute for professional saddle fitting. Changing the gullet width alone does not address every aspect of saddle fit — panel contact, balance, and twist must also be appropriate for the individual horse and rider combination. A saddle that is correctly widened at the front but sits unevenly across the panels will still cause discomfort and back problems.
It is also worth noting that saddle fit should be checked at least annually by a qualified saddle fitter, regardless of whether the saddle has a fixed or adjustable tree. The British Horse Society recommends working with a Master Saddler or Society of Master Saddlers approved fitter. Related reading: Saddle Fitting, Saddle Tree, and Gullet.
Frequently Asked Questions
How do I know if my horse needs a wider or narrower tree?
The classic check is to look at the saddle on the horse’s back without a numnah or pad, and observe whether there is adequate clearance over the withers (you should be able to fit three fingers between the pommel arch and the top of the withers), whether the saddle sits level and balanced, and whether there are any obvious pressure points under the panels. White hairs or dry patches under the saddle after work can indicate pressure. A qualified saddle fitter will use a gullet gauge and assess the contact of the tree points on the horse’s shoulder muscles to determine the correct width.
Can I change the gullet plate myself?
On most saddles with a removable gullet plate system, yes — the manufacturer will supply different widths and basic instructions. However, you should still have the result checked by a qualified saddle fitter, as changing the gullet width also alters the balance of the saddle and the way the panels sit on the horse’s back. Making adjustments without checking the full picture risks creating a new fit problem while solving the original one.
Are adjustable tree saddles as durable as fixed tree saddles?
Quality adjustable tree saddles from reputable saddleries are comparable in durability to fixed tree saddles. The key is the quality of materials and construction — a well-made adjustable tree saddle will last many years with appropriate care and maintenance. Less expensive adjustable saddles may use lower-grade materials that wear more quickly, particularly around the adjustment mechanism. As with any significant purchase, buying from a reputable manufacturer and having it professionally fitted is the best way to protect the investment.