Why isn’t my fruit tree flowering?

03.05.2024 - 14:16 / irishtimes.com / Fionnuala Fallon

A pattern has emerged that I do not understand. On planting a new plum tree, it takes a couple of years to establish and then flowers and bears fruit for several years, whereupon it stops flowering altogether and just puts on growth. The same thing has happened with damsons and greengages, but apples and medlar in the same area are trouble free. My orchard sits on light, sandy, well-drained soil; the ground is manured at planting and a 1m grass-free circle is around each tree for its first five years. Have you any suggestions to get the trees reflowering? NH

There are several possible explanations as to why your plum tree isn’t flowering and fruiting (no pollinated blossom, as I’m presuming you already know, means no fruit). One is that the blossom is being damaged by frost or icy winds before it has a chance to properly open (plum trees flower earlier than other fruit), which can happen in a bad year or if the tree is growing in a very exposed position.

Bear in mind that as a tree matures, it can gradually grow above the protective cover of nearby walls and hedges, with the result that as it gets bigger its blossoming branches can become much more exposed to late spring frosts/cold winds, etc, than when it was a young tree.

Conversely, another possibility – and one that’s increasingly becoming a problem as a result of climate change – is that your plum trees aren’t being sufficiently exposed to cold temperatures during the winter months for them to successfully bloom the following spring.

Known as chilling hours, a plum tree typically needs approximately between 700-1,000 hours of being exposed to a temperature between 0-8 degrees over the course of winter for its flower buds to properly develop and to open at the