Claudia,

Since the bed has apparently been growing irises for a while already, chances are the soil is depleted of certain nutrients. I recommend you collect a soil sample and have a soil test run by your county extension service so you know exactly what you're starting with. That's really the only way to know for sure what your soil needs in the way of amendments.

Overfertilization can damage your soil and poison your plants, and underfertilization can leave your plants lacking for essential nutrients. A soil test will make specific recommendations for fertilizers and amendments to bring your soil into optimal condition for growing irises.

Happy irising,

Laurie

Thanks Laurie. I will do that tomorrow. I always forget about what great help I can get from my local extention center.
Many Thanks!
Claudia