Thanks to both of you. All things considered, it is probably best if I
plant a dozen in a row, and then remove all but three females and one
male (I have plenty of space, and deer chomping in the winter will also
play a role). Such is the luxury of living on sandy soil, if it was
clay I would not even think of digging 12 holes. Removal will be based
on sex and berry taste and productivity.

I noted the warnings about staining mulberries and the chance of
tracking them into the house, but this will be 200 ft from the house,
away from the beaten paths. All I want is to be able to spread a tarp,
shake a tree, and get into the house with a bowl of fresh berries. If
they can provide that for 6-8 weeks, and deflect bird attention from
the raspberries, that is a great deal.