Gravel Garden Versus Hardwood Mulch for Japanese Iris

A. Japanese iris. May 2013 B. Japanese iris. May 2013 Compare the two photos. Both clumps of iris are healthy and happy. But if you look at the companion plants, you'll guess which one is mulched with gravel and which is mulched with ground hardwood. Iris "A" is planted between a hedge of rosemary and butterfly bushes in the sunny gravel garden. The gravel garden was installed in 2011 and I've not had to add additional gravel mulch around the iris. A little raking or leaf blowing is all that is required to keep the gravel garden looking tidy. This spring has been cool, but even in the hot 2012 spring, the blooms were just as lovely. A month ago, I cut the clump in half to share with my son as it has grown so well in this location. The iris is planted in the dip that makes a dry stream, so in heavy rains, the runoff water is channeled here. Iris "B" is planted with astilbe, flowering tobacco and bee balm in a part shade garden where I use ground hardwood mulc...