Gypsum for heavy Mid-Atlantic Z7 Clay?
I can't even remember where I read it at this point, and my search of the iris forum here didn't turn anything up, but I did read somewhere that gypsum should be added to the soil to aid in drainage when planting Iris. I live in Washington DC and we have good old-fashioned clay.
I believe I came upon the gypsum suggestion when one Gardenweb member warned against the use of my normal soil amendment, Bumper Crop, since she found the East Coast variety to contain high amounts of Nitrogen.
After trying to balance various recommendations on the soil preparation and fertilization of Irises, I purchased one bag each of Espoma Gypsum (for drainage), Bone Meal, and Bulb Tone (the latter two for fertilizing). I was told that if using the Bulb Tone, which has a Nitrogen count of 4, I wouldn't need to use the bone meal.
Any thoughts are welcome.