That's going to be difficult I think. It will depend on the varieties used.

Most "wildflowers" are perennials which means they won't bloom until the second year, especially in your shorter growing season. So I would look to find a "wildflower mix" that is labeled as all annuals or a mix of annuals and perennials and get them started ASAP. See link below for an example and Google pulls up several other sources.

Good luck.

Dave

Here is a link that might be useful: All Annuals Wildflower mixes

Yeah, after thinking it over we realize it won't work. Thanks for the advice!