The Help Desk
Morris Lacey, Master Gardener

In 2018, my wife and I purchased a 4-in-1 plum tree. You know the kind: all the rage for plum lovers because the fruit ripens per variety over a longer period than a single varietal tree. We chose a spot in our backyard and planted it where it would be bathed in sunshine. It took off growing and we were confident it would excel in short order.

As a 2019 MG graduate, I remember one of the final exam questions dealt with a hotline call regarding a multi-varietal tree which the gardener complained the grafted branches were diminished and appeared to be dying. The tree was rather mature and there was no visual damage from pests. What could possibly have been going on? While most of my classmates and I got points for our answer, we were left in suspense as to what caused the reduced growth of the branches and what actions the gardener should take to improve the situation (as sometimes that happens with phone calls and pictures).

I did put some time in on the MG Helpline after graduation and remember seeing one call recorded with similar parameters. Again, it was a mature multi-varietal tree losing a grafted branch under its canopy with no noted infestation or disease. This spurred me to take a hard look at our 4-in-1 plum and observe what was happening to it. Could this future outcome be prevented with our tree?

Our tree had bloomed and produced fruit each year since being planted. In 2021, all the fruit ripened at the same time. Interestingly, two of the grafted scions appeared to be losing ground while the other two were raging. Was I setting us up for failure? What could we do to change the future?

We remembered our training: pruning can impact apical dominance and force growth to other branches. In our 4-in-1 plum, the root stock was one of the varietals and formed the largest branch, and a second varietal graft was as big as the main stock. The other two grafted branches were less than half the diameter of the other branches.

Proof is in the pudding! We pruned to give the smaller branches apical dominance and the result this year has been growth – both in height and branch-width. We are continuing to prune for apical dominance and ensure each of the varietals compete in par with each other for nutrition. It is very rewarding to see the smaller grafted branches gaining on the larger ones. We also thin the fruit, so the branches are not damaged by the weight of the fruit.

I am not completely sure the other two hotline calls I mentioned would have responded to pruning as mature trees, but I am certain our efforts on our tree will result in 4 varietals fruiting amply each year if we pay attention to managing the growth of each and balancing their growth as equally as possible.