seegaye, check for Pythium root rot. The outer tissues of the root slide off easily leaving a thread - like structure.

That sure is what I'd suspect, too, Ron.

Do I pull up the plant to look? If they have it, what caused it and what do I do?

i dont know how you look at the roots without pulling one out ...

do it.. snap a pic.. and tell us what you find.. THEN we will discuss what to do about it ...

are these recent transplants ???.. did you amend the planting hole???

you said: same symptom in varying degrees of severity - up to 12 now.

==>>> and this is why it is often suggested.. that you diversify a planting ... rather than planting a lot of one thing ...

ken

ps: use google images to see if it all looks familiar ...

'are these recent transplants ???' :
No. They have been there for about two years.

' did you amend the planting hole???':
Cannot recall exactly since it was a couple of years ago that I put them in, but my general practice is to check drainage, dig that hole larger than pot, and add in a garden mix recommended for whatever I am planting.

'and this is why it is often suggested.. that you diversify a planting ... rather than planting a lot of one thing ....' :
The plants were chosen because I had three or four if them in that area doing very well but had failure with two other types if plants I was trying to grow in that area - not this symptom - just chose wrong ones through ignorance. Moved the other varieties and they are now fine and thriving. After seeing how well other Pitts were doing I decided to run with it. It is a long walk and a big area and I was out of ideas. I am not a seasoned gardener - someone who was may have made a better choice.

Google...:
Looked but didn't find what I could readily see as familiar to what I am seeing. Felt that people on this site could / would be helpful and give best advice.

'i dont know how you look at the roots without pulling one out ...' :
You are absolutely right. It was a really stupid question. I had just awakened and was not thinking.

The 12 plants affected are not all in same proximity. There are healthy looking ones near affected ones. Perhaps a matter if time? We have had recent heavy rains. The area is on a downward slope but drainage has not been problematic in the past. It is dappled high shade with oaks nearby.

Attaching photos. I did not see or feel anything odd in the roots but as I said,I am rather new at this.

Thank you for the help.

Photo 1

Photo 2

Seegaye,
Unfortunately, pittosporum are one of those bushes that are VERY susceptable to root rot.
THey do great in sandy soil, with excellent drainage, but they will rot fast, once it sets in.
You also mentioned in a previous post that you had other plants that didn't do well there either.
There seems to be something wrong with the soil, not enough drainage somehow.
i would dig them all out immediately, and get rid of them.
Just in case it is contagious. You never know.
Then, look at the soil.
Remove all the mulch in an area, dig a hole and fill it with water. Then wait.
Dig a nice size hole, about 8 to 12 inches deep.
See how long it takes for the water to go down.
If the water is still in the hole after dinner tonight, you have a problem.
I would buy plants that love wet feet.
Buy some manure, and plant them where you had the pittosporum.
There you go, problem solved.
By the way, I have 5 big pittosporum tobia out in front of my house by the street, and a really big varigated one in a pot on the side of my house.
I have real sandy soil, (not the potted one), and the water drains really fast, no rot .

Thanks. I was afraid that I might hear something of this sort. Sad to have to let them go as they looked so nice there for so long, but apparently those days are past as they are not happy there now!

The other plants I tried were dwarf azaleas (Vivids) and Indian Hawthornes. The Azaleas just didn't thrive. In retrospect I don't think I watered them enough to get them established. They never showed signed of disease. Moved them and watered them well and they look great now. The Hawthornes didn't get enough sun. Again / moved them and they look great now.

I will follow your advice, and perhaps I should go ahead and remove the healthy ones too - put them elsewhere.

Thank you.

Well, it's not the drainage. It took less than 10 minutes for the hole to drain. We did have some heavy rains for a couple of weeks and I also had planted a hedge of Anise uphill of them that I watered in quite heavily almost daily for a week or so, and then quite frequently on the week after that. Could that have caused it ?