After the first growing season in the ground, ceanothus should not require any additional irrigation. In fact, that is pretty much a guaranteed method of killing them. Yellowing leaves are a sure sign of too much water.

This is what I thought, but the 2nd summer it was watered very little (maybe 1.5-2gal every 10-14 days) and had this exact problem. I even started that summer with the water off and it was doing poorly, so I gave it more.

Is it 1 season always, or is that dependent on the size of the shrub and the amount of water it got intially? I don't think it got enough the first summer and that winter was very dry.

It only needs water the first summer after planting then none. It is extremely sensitive to any summer irrigation.

Xera Plants: " Full sun and average, well drained soil. Light consistent water to establish then none. "

Calscape: " Plant in full sun in well draining soil. 'Dark star' requires little or no water in summer. "

Oregon State University: " Sun, drought tolerant, best if grown with little or no summer water when established, need good drainage, does well in nutrient poor soil. "

I understand this, but then why did it do so poorly, in the EXACT same way, the other summers? The first being it’s establishing summer, and the second with “little water”?

I can't answer that question......sorry. I don't know your weather for that period, how well your soil drains or how much a "little water" is. All I can suggest is that after that first season, the shrub should not need any additional watering aside from what Mother Nature provides.

Don't water it in the summer. You will eventually kill it.

I am sure you are all correct about the watering. But I'm wondering about the paradox that how Ceanothus thrive here where they get rained on copiously all year round. Drainage perhaps? RHS says 'moist but well drained ' for this cultivar.

floral_uk z.9/9 SW UK, from what I understand, it has to do with ground temperature, not just water. They can take rain when it is cool, but not in California summers which are normally dry. They like good drainage, not roots sitting in water.

Seems a good theory. I also think that it is normal to drop some yellow leaves, just as all evergreens do. My neighbour has a hedge of Ceanothus and they do it.

Thanks all. I turned off its irrigation completely and I guess I’ll see what happens over the summer. I was told by a neighbor who works at the botanical garden that it needed water last year when she saw it, which is what set off my confusion. (Also reminded me to turn off the irrigation on the manzanita in the same bed!)

Floral_uk - yeah, I wouldn’t be worried if it was just a few, but this is leaving bare sections of branches. You can see in one of the pics the impact of last year’s loss.