Some of the ideas expressed by Bill Rae, 28-Feb-2016. Compiled by Don Harwood.
Remove excess growth to allow light into the tree and onto fruiting buds
Stimulate new growth. Heavy pruning stimulates lots of new growth but less fruit production.
Shape the tree, pyramid or open vase shape typically. Vase has only one layer of branches extending from the stem.
To limit tree height and width
Remove diseased, dead and deformed wood
If summer pruning is done for stone fruit, winter pruning is normally not required (unlike apples).
Directly after fruiting
Spring pruning encourages regrowth
Summer pruning retards regrowth
Stand some distance from the tree and look at it to get an overall idea of its current shape. If previously considered and a plan or shape for the tree has been decided, continue on that scheme, but some trees just don’t appear to like doing what you may have decided, a tree planned as an open vase may well like growing vertically and not have branches that grow horizontal, so it may be time to change the planned shape of the tree to pyramid for example.
Decide on form, or continue to develop form as previously decided, pyramid or open vase. Don’t be afraid to change your mind if the need arises. A mistake this year can be corrected next year.
Think about what needs to be removed, initially at least
Three D’s first (dead, diseased, deformed) , then look again at tree to see how it is shaping up
Diseased may be to remove “silver leaf” fungi infection, in which case the whole branch needs to be removed during the growing season.
Deformed refers to shoots or branches that cross over each other, one shading the other, broken branches, branches heading in the wrong direction to that desired for shape. (or get in the way of the mower).
Keep in mind
Plums mainly fruit on 2 to 3-year-old wood, so removal of all this year’s growth will remove most of next year’s crop.
Getting light into the tree is vital. No light, limited growth, no fruit.
Horizontal branches produce more fruit than vertical ones.
Use sharp secateurs for cuts on branches smaller than 1/2 inch in diameter. Use loppers or a pruning saw for larger diameter wood.
If using saw, make a cut on the opposite side that one intends to cut from, so bark is not ripped off as cut is completed.
Cut thin diameter branches 5-8mm above a bud that is facing in a direction you want the new branch to grow. Make the cut on an angle to shed water and promote faster healing
Remove dead wood, not a lot of thinking required for this step.
Remove diseased wood, it has to go, regardless of if it is in the right or wrong place, it can be replaced in time with new growth.
Now take another good look at the tree, with the plan in mind, initially, some (one) branch(es) will stand out as needing to be removed, (crossed over, blocking light, heading the wrong way etc), so do that, then stand back again and observe. The removal of a branch can have a significant effect, often more than expected to the overall look and amount of light that appears, so a slow considered approach is recommended, not the amateurs’ “slash and burn” technique. Take the time to really “look” at the tree after each operation.
If shoots are small enough, can break it off by bending it back against the direction it is growing in such a way that the basal buds are also removed, reducing the necessity of a return visit to remove the new shoots from the basal buds if left in place as would be the case if the shoot was cut off.
If removing large horizontal branches, cut off in sections because as the weight is removed the branch will rise and may become ‘wanted’ due to its new position. Cut the branch at a weak lateral to halt continued growth in the direction of the offcut at the desired point.
Seal large cuts (typically cuts too large for secateurs) with wax, “bac seal” or similar product to reduce chances of infection, especially if “silver leaf” is in the area (or PSA if doing kiwifruit).
Vertical shoots (water shoots) = vigorous shoots with vegetative buds growing vertically from existing branches or formed structure. May also be horizontal as well. However, as plums fruit mainly on 2 & 3-year-old wood some of the new shoots (1st year wood) need to remain to carry next years’ fruit .
If small (done early), can be “rubbed off”.
If removing close to the base, cut 2-3 millimetres above joining point. The basal buds at the base of the water shoot will sprout resulting in a return visit required to remove them, but if done in a timely manner when still small enough, they can be just “rubbed” off by hand. If not done, multiple shoots will develop from that point. One of these shoots may be selected and left for next year’s fruiting wood, or future tree structure wood if a major branch has been removed for some reason.
If leaving some water shoot growth (for fruit etc), leave say 300mm or so and cut off immediately above a “weak” lateral as this will stop further extension of the water shoot. If the shoot is in the wrong position in the “long time” view, it can be cut at 300mm to stop extension and bear fruit, then removed the following year to be replaced by another shoot. This is known as “replacement pruning”, some shoots are left to carry next years’ fruit, while older shoots that have fruited are removed, so the tree has some fruiting aged wood at all times.
Small twigs doing nothing, as this helps control passionvine hopper (fluffy bums) (they need small stems to hang on to)
Spindly growth (that has lacked light in the past) that may be shading lower branches, they also don’t form a strong joint to the tree and may fail (break off in the future.
Good quality hand saw, will keep its edge longer.
Diamond sharping file (available from Bunnings for $25)
Methylated sprits in spray bottle to sterilise tools between trees.
Other random tips
Billington plum is recommended as first choice, definitely if only one plum type planted. Can eat from almost green until nearly totally mushy and retains good flavour. Good pollinator for other plums (black-doris, …).
Remove Jasmine from the property, it harbours Passionvine Hopper in a big way.
Nectarines, plums: Cold winter, warm spring in Oct means good fruit. Cold snap in Oct will reduce the crop total.
Propagation: Can propagate stone fruit using the pruned first year shoots. Use first year wood with vegetative buds. Cut shoot about 200mm long, leave 3 buds at the top. Cut out remaining buds. Create a wound on the bottom end by removing a thin slice of wood off the bottom of the stem about 20mm long. Dip in rooting hormone. Plant in a warm place. Hope.
Curly leaf: Remove old wood. Nitrogen in spring to help new vegetative growth (leaves).