In case you missed it, I reported in another very recent thread that I planted calla bulbs last year on April 20th and I harvested the first stem on June 6th, 2008. I think your schedule should work out pretty good since callas continue to bloom for a long season. (I'm on the other side of the country but the same climate zone more or less.) The Pacific Callas web site says that callas will stop growing if the [soil] temperature is under 55 degrees so you have to calculate your bloom target based on the soil temperature not necessarily your planting date.

Thanks for the response Steve, I have been watching your calla thread and very envious of your beautiful calla patch. I had thought that perhaps the colored callas behave a little differently than the white, perhaps not so hardy, is this wrong?. I would love to know that the colored ones are as hardy:). Kat

No, unfortunately the colored varieties are not as hardy as the large white varieties. But it should work fine to grow them according to the same schedule. But you will need to dig them up and store them in sawdust in your basement overwinter since you are in zone 7. They are only hardy in zone 8. :(

Good to know Steve. I just this weekend was in Charlotte visiting my mom who is undergoing chemo for colon cancer that spread to her liver. I went by a nursery and they had just gotten a delivery of a purpley colored calla lily which I purchased for her and was wondering if they would survive her zone 8ish garden. Probably will advise her to keep them inside over the winter just to be on the safe side.