Our all green Phormium, which is probably at least 12 years old, has suddenly developed loads of yellow leaves - maybe as many as a quarter. Can anyone advise on possible treatment?
Phormiums, like lots of evergreens, lose some leaves each year. They can also lose their colour a bit when they get congested.
You can divide them to keep them invigorated. If that's not possible, cut old stems off down at the base and remove anything dead. I've just been doing all mine in the last week or two.
You could also give them a general feed. If it's in a pot, it's necessary to replace a bit of the old soil/compost each year. Ones in pots certainly benefit from splitting and repotting too.