Mountain Ash tree No berries

Asked September 30, 2017, 6:39 PM EDT

My tree is 12 years old. Had berries previous years but not this year. Tree looks healthy. Should I fertilize or what else to consider?

Wright County Minnesota

1 Response

These trees reach maturity at around 10 years, and as a rule fertilizer should rarely if ever be needed by any urban forest tree that is healthy and well established. So, bloom damage or poor pollination are the most likely explanations for the lack of viable fruit production.

Because its monaceous, this tree can in many cases pollinate itself with the help of wind, bees and flies and will flower and produce fruit as long as the blooms are undamaged - by say, a late frost or an untimely severe storm event (hail and high wind).

But as a practical, longer term matter, it could also be that your tree need a pollinizor (another companion tree of like species in the neighborhood).

Both American mountain-ash (Sorbus americana) and European mountain-ash (sorbus aucuparia) are monoecious - ('one house' : Greek) as the flowers are 'perfect' (they have both male and femal structures). Even so, most plants benefit from cross pollination and indeed some plants - and even some cultivars within the same species - are self sterile due to either gametophytic or sporophytic lethal genes that prevent self pollination.

Sometimes if the fruit sets parthenocarpically, then they will fall off as there is no seed in them. To test this explanation you just need to cut through the fruitlets and check to see if there is a viable seed. If not, then you or a neighbor will need to plant another mountain ash that will act as a pollinizor.

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I hope this helps you and thanks for the question!