What causes brown-purple spots on flax plants? (phormium)
Some of the flax leaves are stained by reddish-brown or purplish-brown spots. This applies to what appear to be otherwise healthy flax plants in lots of different environments
Some flax varieties can be susceptible to fungal leaf spot if the conditions they're growing in are rather damp and humid. Flax grow best in relatively open, sunny spots with lots of fresh air blowing around them. So, to reduce the risk of leaf spot, prune away nearby growth to expose the leaves to as much light as possible and allow whatever breeze there is to blow around the plant and dry out the foliage. It's also a good idea to cut out badly spotted leaves close to the base, along with any dead leaves, to reduce the risk of infection. You could spray with a general fungicide.