If they don't have the answer, they might be able to lead you to a Hall of Records or a historical society. I would also check and see with the the American Iris Society and see if they have a chapter in West Covina. Some of the members, if any, may be able to give you some information and maybe even some irises. If you are not opposed to going to Facebook, that is another place you could ask. Especially if West Covina has a presence there.
(I personally don't care for Facebook, but it can be a useful tool in an investigation.)
Please let us know what you find, if you do!