We have three Pittosporum trees (about as high as our one-storey house) but since spring, one has turned its toes up and died. The second tree’s leaves have started dying and I have no idea why. They are beautiful trees for the birds and get enough water as we have a punga tree in the middle and give it gentle watering. Fingers crossed for the third surviving. Do you have any idea what’s happening? No sign of any illness in the leaves prior.
Without knowing exactly which Pittosporum you are referring to, we will assume it is either Pittosporum Tenuifolium or Pittosporum Eugeniodes which are very commonly grown.
While both these are regarded as quite robust plants that grow successfully in a range of soils, they can at times have dead branches on mature specimens, or as you described, can die out completely after a number of years of growth. As with most plants, the better the soil, the better the plant grows and matures. Adding compost to existing soils, mulching over dry summer months and fertilising in spring and autumn all help in maintaining strong, healthy trees. Deep watering over dry summer months, especially when trees are young, is also very beneficial.
You may wish to try growing Pittosporum Ralphii or Pittosporum Crassifolium to replace your dying trees. These are two very hardy and attractive Pittosporum that seldom fail to grow to maturity in home gardens.