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  • Writer's pictureMartin Ford

Heavy flowering years—why? 

Individual tree species (this year its locust and walnut in our area) are beautifully ‘covered’ in flower and, as we will see in a few months, results in heavy fruiting. The previous year the walnuts bore almost no fruit. But what is fascinating is that all the trees of one species ‘coordinate’ this ‘decision’. How they create this communication the year prior, which then internally ‘triggers’ each tree to provide the resources to initiate the flower buds to form and be ready for the following spring—and then provide all the carbohydrates and minerals to make something as complex as a fruit or nut—we have no idea about.  

But we cannot avoid recognizing the reality that this was a ‘community’ decision by all these individual trees, often miles from each other, and so we are left in wonder as to why they chose so differently from previous years of minimal flower and fruit. 

In the past we have speculated that trees do this to maximize the chances of some seeds not getting eaten and instead having a chance to germinate and so become the next generation. The heavy flowering and fruiting requires an extraordinary effort by the plants to focus all their resources to enable this ‘wonder’ to occur, but this they are indeed able to do, as we see with commercial fruit trees in orchards. So, the ability is there each year, but the tree/s somehow prefer to form a cohesive decision to fruit all together at the same time—as a community effort. Maybe this heavy flowering creates the greatest chance for genetic adaptation to changing climates, for example.  

We’ve known that fruit trees in orchards will become biannual bearers of fruit (bearing fruit heavily one year and lightly the following year) if we do not thin out the fruit set (crop) one year so that the following year will have a similar, normal flower formation. If in one season there is a lot of seed formation during pollination and it is not thinned out, it will cause the trees to initiate far less flowers for the following year. This thinning also creates better quality fruit as the tree's resources are evenly distributed from year to year. 

We also recognize that when a tree is preparing to die, that during the previous year it will have produced an exceptional amount of flower as a final effort to create as many seeds as it can and use up all the internal resources it has available—it knows that holding back nutrients and carbohydrates for the years to come is no longer necessary and so the next generation is its priority in its final year. This is an individual tree's decision rather than a community coordination but clearly the tree is deciding to heavily flower and fruit so that it can maximize the progeny chances for future succession of the species. In each case, we recognize that the tree or the community of trees is using heavy flowering to enable the most effective future for the species—a very 'selfless' act. 


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