Question
When is the best time to prune what we think are native post oak trees in north central Texas.

Answer
While deciduous trees can be pruned anytime during the year, the best time to prune is late winter or early spring before the trees leaf out. To prevent the spread of oak wilt, avoid pruning oaks from April 1 to July 1. Pruning oaks during this period may attract sap beetles carrying the oak wilt fungus to the pruning cuts and transmit the disease to healthy trees. An excellent time to prune oaks is February and March.

Pruning methods are best dictated by your purpose--whether to keep the tree a certain size or shape, or just to tidy it up. Pruning in late summer can encourage new growth which can be cut short at the first frost and impede next spring's growth. In the fall, prune when frost is imminent and leaves are falling. In spring time, prune before new growth is under way. Never prune a tree in mid-growing season because it will be less effective and may shorten the life of the tree.


Prune the dead branch off about 1/4 inch from the trunk. This will leave a branch collar and the wound will heal over by itself. If the wound is more than 6 inches across after the cut I would paint the area with a wound dressing. This will keep water from getting into the wound. On wound less than 6 inches across I would leave natural and not paint.

On large trees it is best to make the first cut about a foot from the trunk on the under side then cut the branch off from the top leaving a stub about a foot long. Then you can prune off the stub and the heavy limb will not split the bark on the trunk.
Here is a web link to how to prune trees with a drawing of the large limb pruning method.
http://www.ces.ncsu.edu/depts/hort/consumer/factsheets/trees-new/text/pruning.ht...


Don't prune more than twice a year, and never remove more than one third of all the branches in any one season. It is best to prune selectively every year, rather than removing too much growth at one time. To encourage taller growth, cut back lower branches gradually over about five years. Removing too many at once will result in a weaker, stressed tree that is more prone to disease.  

It is never a good idea to top a tree. The most common reason given for topping is to reduce the size of the tree. Often homeowners feel their trees have become too large for their property. People fear that tall trees may pose a hazard. Topping however, is not a viable method of height reduction, and certainly does not reduce the hazard. In fact, topping will make the tree more hazardous in the long term and will probably even destroy it.

This cuts the terminal stem and will more than likely cause the tree to be bushy or have a forked trunk. Hardwood trees will sprout back after a pruning but will look ragged for a while. As a result of the topping, limbs sprout from the cut or topped areas and are growing improperly. This is the tree's response to the topping cuts. The limbs are growing out of control, because the tree has lost the ability to maintain dominance on its main leaders.

The limbs growing from the topping cuts grow more quickly than before thus they are more weakly attached and not as strong as the limb removed. This is one reason why topped trees maintain a higher percentage of breaking, cracked, and falling limbs during ice and wind storms.