About two months ago I planted about 20 Bambusa Oldhamii mature culms
(cut about a meter high), with roots.

Three of the plants have sent up new shoots which are now a couple of
meters high and about an inch thick.

I am in the southern hemisphere (New Zealand) so it is mid summer here,
our year round climate is temperate, not many frosts.

My questions was, does this variety of bamboo send up new shoots at
random times? Or is it only supposed to shoot once a year. When could I
expect the other 17 plants to send up a shoot?

Regards,
Andrew Ward.