Here is one adjustment schedule I saw online, but NOT adjusted to zone 9b:

July, August, and September: 100%

October, May, and June: 80%

November, March, and April: 50%

December, January, and February: 20%

Zone 10, east Bay--I turn off mine once fall kicks in (after it stops being hot).

Plants selected for a Mediterranean climate as well as natives should prefer it. And established shrubs seem to be okay with it as well. I don't have rhodos but I have 60 year-old jades, camellias, tropical hibiscus, etc. that are fine with this regimen, along with various citrus and pome fruit trees.

Anything that needs more water (once established) doesn't make it in my yard.

Rhododendrons might not be ideally suited for our climate but I have never actually tried to kill any here. I mean I have no experience watering them in this geographic area. I bet they want watering. :)

Just guessing cause it 'depends' on weather, I have 14 Zones - 2 just for pots

with rain - 0%

Summer 85-100 % matching the temps roughly, for conservation this year I kept it at 85%

Fall and Spring 70%

late fall and early Spring 50%

Lawns only, winter w/o rain 25%; others are 0% except pots (on drippers) which are 25%-50%

Vegetable garden gets more % and more frequency

Most of my 'winter growing' plants like Bulbs are in no irrigation zones and must be hand watered in drought.

For Winter, Zones in shade get a bigger percentage reduction than those in Full Sun as they hold moisture for a month or more.

gardening is an art.. not a science ...

and when you make it into a science.. imo.. its just no fun anymore ..

i dont understand.. with the vagaries of mother nature.. and her weather.. how you could expect anyone to come up with a system of what you should do in your yard.. in your soil.. with your ambient weather ...

and surely minimal winter temperature.. zone.. has nothing to do with winter watering .. so why are you fixated on that ... temperature is one of lest important WINTER issues.. dont you think??

also.. if you were somewhere where you actually had a winter.. i would tell you that dormant plants dont need much water at all.. but i surely dont know z9 nor CA... but you need to take that into consideration ...

do your plants even go dormant for winter??? .. teach me something ...

ken

All my watering is by hand, so I have no opinions about drip irrigation settings, but I can give Ken some information about plants suited for Mediterranean climates, such as my zone 10b.

Most of my plants do NOT go dormant in the winter, in fact late winter/early spring is when they have their best growth. If we have a good rainy season that is enough. If we have a drought I need to water them in the winter. I rarely water the Mediterranean climate plants in the summer - they are used to no summer water and that is when they may go dormant. They don’t necessarily lose leaves, but they just sit and do nothing until the fall rains.