How to amend clay for bearded irises?
I have posted some messages in the Iris forum as I prepare to plant Irises for the first time in my garden and I ran into a roadblock when one member told me that Bumper Crop, my usual go-to for amending the soil in my Washington DC brand red clay, is high in nitrogen and thus a potentially disastrous choice for irises. I have a special no-Nitrogen fertilizer from the grower and I've added gypsum to improve drainage, but it is also recommended that I add compost. Aside from the gypsum I have added nothing yet to the bed.
My question now is what sort of compost I should use for irises, and if there's a way to find one with low nitrogen content. I checked the Leafgro site since it produced locally and widely used here, but it provides no information.
If anyone has any insights on how they treat their soil, or if they have any experience with irises, I would love love to hear from you.
Any thoughts are appreciated. Thanks so much!