does blackberry produce fruit every year

Question

I have a blackberry tree in my yard and last year it produced a lot of fruit. In past years, it did not bear any fruit. This year it is producing fruit again. The tree has been in my yard for over 30 years.

Answer 1

I believe you may be referring to a Mulberry Tree.

The environment and it's changing weather can effect how much or even if the tree bears fruit.
Many gardeners dislike the mess from Mulberry fruit.

Here are a couple of links.

http://www.fruit.cornell.edu/mfruit/mulberries.html
https://www.gardeningknowhow.com/ornamental/trees/fruitless-mulberry/mulberry-fruit-sterilization.htm