Thank you, @hoovb! This is exactly what I was looking for and will implement this starting now. One more q about the lavender: is it okay to cut back the lavender now that we're in March, or should I wait until fall? I'm afraid if I wait too long that the plant will completely die.

Cut Lavender back either before it starts to form blooms or after it has bloomed. If they are really yucky, whack them anytime except when they are blooming.
Azaleas like acidic soil, humidity and afternoon shade, esp in So CA. Live your drip on them, but maybe spritz them in the mornings or evenings (whenever the drip is not on).

It is better to deep water roses, esp in a hot climate. Water more less often, esp now while it is still cooler. This forces the roots to go down, keeps them cooler when it gets hot, makes for greater stability. If you water often on the surface, the roots stay on the surface, dry out more quickly, need water more often. Also, in clay, too much water may accumulate if you water even every other day and you will get root rot. So, I'd water just twice a week until the end of May or until it hits the 90s. Then 3x/wk.

Is your clay soil natural, or is it engineered soil in construction within the past twenty or so years? Does it drain well or remain soggy after either heavy watering or rains? If you live along the coast where it's generally more humid and "hot" is in the eighties, the amount and frequency of watering will differ greatly from what would be appropriate if you live in a hotter (nineties to low hundreds), more arid, perhaps even windier inland valley. Don't forget that magnolia is going to suck a lot of water away from those plants within its root zone. Kim

The magnolia has surface roots that may spread out 30 feet. I have a magnolia also. When I planted my front yard floribunda garden I had to dig through magnolia and camphor tree roots. Since the drip system doesn't waste water, I run mine several times a week and even after the recent heavy rain the moisture meters never showed more than moderately moist.

My lavenders are pushing out new growth now. So, go ahead now, but in future years do it after a round of bloom (those that repeat) or right after bloom (those that bloom once in spring).

All lavenders are not the same, if you can find a Goodwin Creek Grey mine seem to just keep on blooming non stop. The one that is getting too much water is bigger than the one that is getting less. Mine have spread to the 3 foot size (and yes I planted them thinking they were going to be 2 footers....)

I love the greens and deeper tones of Hidecote, it blooms less so far for me, but I will be adding more of this one. It is also much smaller.

My Munsteads are growing much slower so I really can't tell you much about them.

If you have space and want non stop flowers...Goodwin Creek Grey is a winner.