· Brent Wilson's Answer
· Hi Kevin,
If your dwarf pittosporum has or had dark green leaves the variety is probably "Wheeler's Dwarf." If so, it could be a number of things causing the leaves to turn yellow-brown in color on your plants.
Our nursery here in zone 8a of mid-Georgia quit selling Wheelers Dwarf many years ago because of a tendency for the plant to develop chlorosis (a yellowing of foliage) and overall poor performance. The Variegated Pittosporum does great...but not the Wheelers Dwarf. Our clay soil is typically acid, which should help to keep the foliage green on dwarf pittosporum, but the foliage still turns yellow. This usually happens during winter so I assume it has something to do with cold temperatures and/or too much soil moisture. Zone 8a is right on the margin of where Wheelers Dwarf Pittosporum is winter hardy and, during winter, clay soil holds a lot of moisture. Pittosporum prefers well-drained soil. Consistently wet or soggy soil will cause problems with the roots that will show up on the foliage as leaf spots, or yellow or brown leaves that eventually drop from the plant. If drainage is not improved the plants eventually die. So, I think it's a combination of cold temps and soggy soil that the dwarf pittosporum can't tolerate.
If not cold temps and soil moisture, the yellow-brown leaves on your pittosporum could be caused from a number of diseases known to attack some varieties of pittosporum in certain areas of the U.S.. If you can upload a closeup picture of the foliage perhaps I or others could determine whether or not your plants are suffering from a disease. To upload a picture, click on the 'Upload A Picture' link to the right of where your name appears above...next to the 'Edit your question' link.
But, if your in Zone 8a in the Southeast, I'd say it's just that the plant does not do very well in this region.
Hope this was helpful and let me know if you have any further questions.