sorry, can't find the picture anywhere, maybe you can post it again?

Do you think frequent mowing and re-seeding a few times a season with hardy grass seed will perhaps choke them out? No, nothing will choke out that bulb. I could show you some amazing pics...sometime later, like where it forced itself up through the blacktop drive that was put in the previous fall. What you 'might' consider doing, is solarizing the soil in the very hottest part of the summer, for maybe 6 weeks, and hope that it maybe bakes the bulbs. Clear plastic I've read, will warm up more underneath than black plastic. You could try a section of the lawn this summer, and then reseed that portion this fall, and see what the spring might bring. The link below tells how to solarize the soil. The same garden center that incorrectly told me it was Scilla also recommended that I pour a mixture of lemon juice and vinegar into the deep holes that I dig the clumps out of - that the acidity would kill any little bulbs left behind. What I do, is dig on my hands and knees and am careful to get additional soil with the clump of bulbs, and check to see if there is any green foliage around the sides of the hole. I doubt if your salad dressing is really doing anything except wasting your time and $$. I use a bulb planter to dig down deep enough to get at the bulbs, so my yard looks like a demented putting green. Mine looks more like a battle field, and am just thankful for the beds I have that are bulb free. On one bed I made, I dug it out to a depth of about 6 inches, and then brought in good woods dirt that was bulb free. Here is a link that might be useful: How to Solarize Soil

It is not swamp or LA iris which has foliage present all year long from my experience and grows from rhizomes. This is a bulbous iris. I agree with Saltcedar. Scroll down half way. This is copied from that site: Iris xiphium, which is the Spanish iris this group is named for, is common in southwest France, Corsica, Southern Italy, Portugal, Morocco, Algeria, Tunisia, Gibraltar and Spain. It has handsome blue and yellow flowers and has been used as one of the parents in the many hybrids known as Dutch Iris. There are four varieties. This iris is quite popular in flower arrangements. Photos by Celestino Gelpi. Here is a link that might be useful: Iris xiphium

It's Nectaroscordum siculum. Here is a link that might be useful: Nectaroscordum