I recently cleaned out a neighbor's iris bed that was really overgrown. I am transplanting iris into my garden and replacing them into my neighbor's bed as well. The article says to space them 18" apart. Can they be closer than that and can I dig into the soil organic topsoil to amend the soil? His bed was about 6 foot square and I have more than 100 rhizomes that I am dividing and replanting. I was thinking to add some tulips and daffodils to the beds.
You can plant them closer together, but they will need to be divided sooner most likely.