I got some new dwarf re-blooming iris and wanted to plant them on a small strip between a concrete driveway (about 1 foot wide) and fence. I know the iris need good drainage, so I was going to dig out 8-12 inches of clay soil and place some extra crush and run gravel. Then fill the rest with a sandy compost soil mix to raise the strip up 2-4". The instructions say the to plant the rhizomes so that 1/2 - 1/3 is exposed. Hopefully this will provide adequate drainage but wondered if the crush and run gravel was a bad idea...not sure what this would do to the PH. Any suggestions. Thanks in advance.