Answer: I'm afraid if you cut the foliage down to 12", the leaves will remain that size and new growth will continue to emerge on the outside edge of the clump. I'd suggest putting up with them the way they are for the rest of the year but planning on digging and dividing the clumps in early spring. After being replanted the divisions will begin growing as small plants, with smaller leaves (because of the smaller root systems). As the summer progresses you can remove the original (longer) leaves and you'll end up with several small and attractive plants. Best wishes with your Phormium!
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