Plant Doctor Archive

Plum tree not fruiting

Any ideas why a perfectly healthy plum tree flowers profusely, forms tiny little plums and then they mostly fall off? I have long lost the label, but it was supposed to be a self-pollinator. I have never fertilised plum trees, but the grapefruit next to them is laden (I fertilise the citrus regularly). Could I have a soil deficiency? Is it potassium for fruit set?

The reason the plum is not setting fruit is likely to be incomplete pollination. Most plums require a pollinator. Some are self-fertile but still require a pollinator. Incomplete pollination occurs when there has been a wet spring (which we have had — bees don't work in the rain!), or frost at the crucial stage of fruit set.

You are correct in saying potassium helps improve fruiting. Plums benefit from regular applications of fertiliser. Once a year apply a general garden fertiliser after flowering, which will help increase the fruit size.

Duffs Early Jewel is a good pollinator for Japanese plums.

Advice by Dr Dan Blanchon from Unitec's Diploma in Sustainable Horticulture and Bachelor of Resource Management.

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