Posts from thinning In addition to the landcare benefits derived from planting trees on farms, a further benefit may be gained from treating thinnings for posts which may be sold or used on the farm. Farmers can produce durable posts which will last 30 years or more by treating the thinnings from plantations, shelter belts or native regrowth. With increasing interest in growing eucalypts for sawlogs, their thinnings may also provide a ready source of fence posts. This TreeNote describes the treatment of round posts on the farm, using high temperature creosote, an oil-borne preservative. Without preservative treatment, the permeable sapwood can be destroyed in a few years by decay or insects.
Durability also depends on the severity of attack by fungi and insects, especially termites.
Advantages of treating posts Posts of low natural durability can be made more durable by impregnating the sapwood with preservative to form a protective outer layer around the relatively impermeable heartwood. Protection of the sapwood also makes a post stronger, as sapwood contributes over half its strength. Pine species, in which the juvenile wood absorbs preservative, are also suitable for treatment. Selection of posts Choose trees that will provide the smallest posts, strong enough for their proposed use. Posts should be straight and free of branch stubs so that they can be closely packed in the treatment vessels.