Taken from one of the FAQ here...If you have the room, plant your rzs about 2' apart with no other plants nearby to overgrow them and compete for soil nutrients. You can also plant 3 separate rhizomes in a triangle 1' apart with the leaf fans facing outwards to produce an instant clump effect.

Think of a rhizome as a foot. The fan is the heel end. It will not grow any longer in the toe. It (the mother rhizome you planted) will hopefully bloom next season, and in the meantime it is growing daughters on the sides.

Sue

Thanks Sue. The strange thing is that growing on the toe is exactly what some of them intend to do. For example, my Baby Blessed is sending up new fans in the traditional manner you describe. But I have a Barndance (one I mean to transplant) and Constant Companion that are sending up fans in columns behind the rhizomes, inches away---soldier style. Again, this pattern is contrary to everything I've read about irises here and in other places, yet they're growing that way.

I guess I should just treat these fans as anomalies and plant according to your advice.

Thanks.

None of what you describe is unusual. After bloom, the rhizome from which the bloom stalk arose is the mother rhizome, which has by the time of bloom, generally produced new fans behind (away from the rhizome) and to the side of the bloom stalk. There will often be small growth buds along the length of the mother rhizome which, in very healthy soil, and with a very vigorous variety of iris, and given good weather/climate conditions, will start to grow into larger rhizomes and put up fans of their own, so you get this scattering of fans all around a strong growing clump - a row each side of the mother rhizome, and a group to either side of the bloom stalk. Each of these will eventually put out their own increase and make a large clump.
The fan you describe coming up 5" away is strange. Could it be a piece of another rhizome, or something that was left in the soil? Sometimes I get rhizomes that are so huge that they have little pea sized rhizomes along the sides, and these can become detatched as the plant is being planted, and fall to the ground and grow by themselves. Some of the ones I have had from Barry Blyth have had babies the sized of a cherry tomato, and it may be hard to know what plant they came from if they have detatched themselves. Still it's a bonus!
Here in Australia, the growing season is such that I often have 2 lots of increase in a season - the mother rhizome produces new increase in Autumn, then another lot in Spring arise from those that grew in Autumn.
Cheers, Jan