Very Pretty!@microchick
Iris rhizomes should not be covered with mulch...or dirt for that matter (too easy for them to rot in our humidity).
Because grasses usually spread by runner and not seed, corn gluten meal (Preen) isn't much help on perennials like Iris but will work around annual crops like onions or in an area where grass isn't a problem.
I find that making the Iris beds my first priority for weeding and keeping the area around them clear works best. If something gets started due to my laziness, digging the Iris out, cleaning the area and replanting makes me more diligent.
I love my Irises,too. This wasn't a good year for them...too cold late and then hot.
Here are a couple pictures:
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