Hi Lemonbird. A couple of years ago, I attended a class featuring a propagator from New Zealand, and asked him the same question. He said that you can even pot up a "fan" without roots and it will eventually put new ones out if you partially bury it. He also recommended that you divide the plants while they are fairly small so that the roots don't get too tangled up (I had just divided a large "Sundowner"). It was also suggested that if there is serious root damage, that you cut back the older leaves, and just leave a couple of newer ones to help reduce shock. Since that time, I immediately divide what Phormiums I bring home from the nursery and all have done well. I think that dividing in itself will help to encourage side shoots. As this is the hottest part of the year it might be a little risky, but if you can split them up without too much root loss, they should do OK. I recently split a 5-gallon plant with no problem at all. If you have a huge clump in the ground, you might wait until Fall -- or better yet, Spring. Hope this helps a little, Junglejim