Herman,
a big thank you. I don't know why, but we never looked up the climate of Johannesburg, though we do have an olive and a Celtis a. from seed. Came from your botannical gardens via some friendly horticultural students, in Florence, Italy.
Seems that you have a six month period during the colder months with little rain. We have a 5 to 6 to 7 month period during the colder months [ 70 deg.F - 22 deg.C - lasts from 5 p.m to 8 a.m - ha ha ha ] of no rain or very little rain. Then back to 15 cm a month with a peak at 23 cm in August.
Our humidity does not seem able to go below 40%, probably due to being a small island.
Another part of the mystery solved.
We have a smaller variety of Punica granatum nana, called - minima, tiny leaves and seems to be well adapted to our climate.
The largest punica comes India back in the 1800's and the next size doesn't really like life down here.
We also had the flowering only type, but haven't seen that for years.
Happy growing.
Good Day
Anthony
* Yes, we can be humid in the valleys, and after rain with sun, or sun and rain. Two weeks in August is our horrible time, though temps. stay around 30 deg.C as highs.