30+ yr old Black Walnut tree in front yard, for the first time has not produced any nuts. Why? Anything to be worried about re tree health?
Thank you for contacting the Toronto Master Gardeners about your black walnut tree. If there is nothing unusual about the appearance of your tree (for example no yellowing or splotchy leaves or leaves curling or dropping, no stickiness or black sooty spots on your leaves, no webbing), then I think there is likely nothing seriously wrong with your tree. There are several possible reasons why your tree has not produced nuts this year. Black walnut trees (Juglans nigra) have a tendency towards alternate or biennial bearing, meaning that they will have a heavy crop of nuts one year, followed by a year of a light or no crop. This typically doesn’t happen like clockwork, one year with lots of nuts and the next with few or none, year after year, but after a year or more of heavy crops, it’s not unusual for black walnuts to have a year with a lighter or no crop.
Lack of pollination is another possibility. Black walnut trees are self-fertile, meaning that they have both male and female flowers. Wind is needed for pollen transfer, and this needs to happen when the female flower is receptive. Having more than one tree helps to ensure a better crop (Have any nearby black walnut trees been removed recently ?)
Your tree might also have been stressed by our hot, dry weather this summer. Black walnut trees do not do well in drought conditions.
Final possibilities for your lack of walnuts this year are that your tree might have been growing too vigorously as a result of over fertilization or over pruning. Fertilizing the grass or plants near your tree could have added too much nitrogen to the soil, resulting in your tree’s energy going towards leaf, trunk and root production, instead of flower and fruit growth. The same is true if you have done any heavy pruning during this growing season.
I hope your black walnut tree will have many more years of good health and successful nut production !