Agriculture, including horticulture and arboriculture, used to be done, to a great extent, by the calendar. The calendar approach has largely given way to a scientific research based approach. Research has shown, for example, that pruning should be done to meet certain objectives rather than according to time of year.The old school approach had been that there was a certain time of the year when each tree or shrub species needed to be pruned. Research has now found that this isn’t true. Pruning should be done to meet specific objectives. Not just because the calendar says it is time.Some pruning objectives include…• Removing dead, dying, diseased, crossing or rubbing, diseased and hanging branches;• Thinning the crown to help your trees better withstand wind;• Raising the crown if branches are interfering with traffic;• Opening a vista;• Repairing storm damaged trees.If any of these objectives exist, this would be a good time of year to have your trees, especially your deciduous shade and ornamental trees, pruned. The weather is cooler. There is more precipitation. The trees are preparing to stop photosynthesis for the season, drop their leaves and go dormant for the winter. In fact, winter itself is also a good time to prune, but only to meet your pruning objectives.Regardless of your pruning objective, pruning is not a do-it-yourself job, especially if you have to leave the ground. There is a reason why we employ only highly trained people, and continue their safety training on a regular basis. And, why the cost of insurance is so high. Tree pruning is a dangerous profession.