Perhaps the key is not growing in a pot, Andy's are in the ground. If they are in the ground, they should be alright with lots of rain.
Now around here - years ago I tried to grow them in the yard, then one year in a pot and didn't succeed. The only way they took off for me and really multiplied was when I planted them right against the sunny South facing house wall.
Goldilocks?
Just the right amount of cold, sunshine and moisture.
