Tim Tyler writes
K wrote:

What do the male catkins look like, anyway? I've had a good look on
my tree this morning and all I can see is what I presume are female
catkins, basically looking like embryonic fruit.

http://waynesword.palomar.edu/terminf1.htm
http://waynesword.palomar.edu/fruitid6.htm4

Scroll down for the pictures.

OK, thanks :-)

Definitely female catkins. I note he says that male and female catkins
occur on different trees (both as a general statement about mulberries
in general, then further down about black mulberries specifically) and
that would explain why I can't find male catkins. But you were saying
that black mulberry is monoecious? And obviously your particular tree is
if you are in a position to pinch out male catkins.

--
Kay