The Santa Rosa Plum variety was developed by Luther Burbank in 1906. This plum variety is to this day one of the favorite of home orchardists and commercial growers.
The best time to start pruning your Santa Rosa Plum Tree is a year after it is planted. Early pruning to develop the proper structure is best done when a tree is young. It is important to keep lower branches on the tree where the fruit can be easily picked. To develop strong branch development prune out branches with high "V" shaped attachments. These are more likely to fail as the tree grows. Branches that attach to
the trunk horizontally are strongest and should be retained.
Fruit trees produce more fruit when they are encouraged to grow new branches each year. Plums grow on last year's new wood. This means that your best fruit production will occur on wood that was grown during the previous Spring and Summer.
The best way to promote new wood is to reduce the upper part of the branches each year.
A good rule of thumb is to remove one third of the new growth and reduce the remaining branches by one third. This keeps new branches growing each year and will keep your plum production high. When reducing a branch you will want to cut to a lower lateral branch that is one third to one half the diameter of the branch you are cutting. Remove any overcrossing branches but keep some interior branches on the lower tree where the fruit is easy to reach. Too often fruit trees are overthinned in the lower tree and left to grow tall where the fruit is too high to reach. Don't make that mistake when training your tree. Keep the lower branches and reduce the taller limbs to encourage new fruiting wood that provides fruit that is easy to pick.
A Santa Rosa Plum Tree can grow to 25 feet or more but is best kept at a height where you can reach the fruit. Most people use a ladder or basket style fruit picker to reach taller branches. So the height of your tree may best be kept where you can reach the fruit with your picker or ladder. In commercial orchards trees are normally kept at the height of the pruning ladder being used to prune the trees.
It is a good rule of thumb to follow in your home orchard as well. Prune the tree to the height you are comfortable when working from a ladder. I recommend having someone hold the ladder while you are working to prevent an accidental fall.
The type of tool used to prune your tree will depend on the size of the branch to be pruned. A good pair of hand pruners can cut a limb of 1/2 to 3/4 inch. Larger branches can be pruned with a pair of loppers, a hand saw, or a pole pruner. Make sure you have sharp tools in good condition prior to starting your pruning. Trying to make a clean pruning cut with a dull pair of hand pruners or hand saw is frustrating and can even be dangerous.