I have a tall (50') black walnut next to my driveway/parking area

Question: I have a tall (50') black walnut next to my driveway/parking area.  I have lived with it for over 30 years.  We really like its looks and the shade it provides, and appreciate that it is probably over a hundred years old. 

Unfortunately, it drops walnuts from incredible heights and damages many things that are under it when it does.  Last year a falling walnut cracked the windshield in a friends car.  It also put a number of dents in the roof of my old Honda Accord. 

I attached pictures of the tree (on the right).  Some have a plastic lawn chair in front for scale.

If there a way to stop this tree from fruiting that is safe an effective?   The crown goes way over the drive and I do not think trimming is an option.....

responder: V/r,  Replied April 14, 2023, 6:54 AM EDT
response: Good Morning, Plant inhibitors have been used by farmers, orchardists and landscape management companies to control the size of trees. The hormone Auxin controls the growth of the plant and growth inhibitors prevent auxin from being secreted and the tree cells are unable to produce seeds or fruit.  If you want to discourage your walnuts from fruiting, fertilize them with nitrogen-only fertilizer in early spring and late summer. The growth of foliage is stimulated by nitrogen, and nitrogen-containing plants produce fewer flowers when used up.  A certified arborist would be able to help you if you wish to sterilize your tree. To find an arborist in your area, go to www.treesaregood.org the website of the International Society of Arboriculture.  How To Stop A Tree From Producing Nuts | Mast Producing Trees (mast-producing-trees.org)  I hope this helps.  Thanks for using our service.

responder: The Question Asker Replied April 14, 2023, 10:07 AM EDT
response: I contacted a local certified arborist.  He emailed be that I could spray the blossoms but, due to the trees size, it would not be practical.  Basically, cutting it down was the only practical way to solve the problems.    I don’t want to cut it down.  I have seen the nitrogen fertilizer answer.  How much does it take to stop nut production?  I am very interested in the idea of permanently sterilizing the tree, also.  Is that possible?  I read the article connected to the link you sent and it has a slightly disjointed feel to it.  It looks almost like it was generated by Chat GPT…..   Thanks,Larry Carter From: ask=<personal data hidden> [mailto:ask=<personal data hidden>] On Behalf Of Ask ExtensionSent: Friday, April 14, 2023 6:55 AMTo: Larry Carter <<personal data hidden>>Subject: Re: I have a tall (50') black walnut next to my driveway/parking area (#0095227)

responder: V/r,  Replied April 14, 2023, 5:41 PM EDT
response: Good Evening, I can't find anything in regard to permanent sterilization for a walnut tree.  As you stated above it is not practical to spray such a large tree.  Unfortunately, a homeowner doesn't have many options: remove the tree, learn to live with the trees natural tendency to propagate, or "try" using a plant flower growth regulator such as Forel Fruit Eliminator.  Home application of hormone regulators can be difficult. The first consideration is timing. You must spray when the flowers have just formed but before fruits begin to take shape. There is no way to get every bloom since the exposure to light and elements influences each area of production on the tree, but you can get the majority. Apply when there is no wind and temperatures are between 60 and 90 degrees Fahrenheit (15.5-32 C.). Follow the application rate recommended by the manufacturer. Choose the correct formula for your tree variety. Some of the chemicals available go under the name Florel, Fruitone, App-L-Set, and Carbaryl. Be wary of their effects to unhealthy trees and to honeybee populations.   How hormones and growth regulators affect your plants | OSU Extension Service (oregonstate.edu)  I hope this helps.

responder: The Question Asker Replied April 14, 2023, 10:40 PM EDT
response: Thanks Doreen!   I really wish there was a magic bullet for this problem that did not involve removing the tree.  Falling walnuts put multiple dents in the roof of my old Honda and, just last year, a large walnut splat near the edge of his windshield took out the entire windshield of a friends Volvo.   Doesn’t sound like there are a lot of practical options other than removal.  Dang. Thanks again,Larry Carter From: ask=<personal data hidden> [mailto:ask=<personal data hidden>] On Behalf Of Ask ExtensionSent: Friday, April 14, 2023 5:41 PMTo: Larry Carter <<personal data hidden>>Subject: Re: I have a tall (50') black walnut next to my driveway/parking area (#0095227)