Most of us Californians are probably wondering what that means. Sugaring season is more familiar to horticultural enthusiasts in New England, Canada, and more recently, in Alaska. It is the time of year that sugary sap get harvested from maples, and in Alaska, from birches. Maple sap gets refined into maple syrup and sugar. Birch sap makes birch syrup and sugar, a recent fad up north.
Why is this important here? Well, maples and birches know what time of year it is. Their sugaring season is relatively brief here; and they do not produce as much sap as they do in cold climates. Nonetheless, their sap will eventually start to flow later in winter, just when we expect it least. By the time we will be pruning dormant fruit trees and roses, it will be too late for maples and birches.
Therefore, maples and birches should either be pruned as soon as practical after defoliation, or after refoliation later next spring or early summer. They tend to defoliate before their sap gets too pressurized. However, if opting or the autumn pruning schedule, it is advisable to prune off one small stem first and then wait a few minutes to see if it bleeds. If it does, pruning should be delayed.
Bleeding may not be as harmful as it would seem to be for mature trees, especially since birches and many of the maples do not need much pruning of viable stems. If they get infested with sooty mold, a few small bleeding wounds on a big birch tree are more unsightly than unhealthy. However, several bleeding wounds can be somewhat distressful, especially for young Japanese maples.
If opting for the spring pruning schedule, maples and birches should be allowed to refoliate first. Their first leaves should be fully developed. This might be difficult for those of us who believe in pruning during dormancy, but it is better than causing sap to bleed when the trees need it most. Pruning can be done during summer too, but summer pruning should not be aggressive enough to suddenly expose formerly shaded bark to direct sunlight. Otherwise, bark can scald. So once again, timing is everything.