Both microphyllas and greggiis root fast and prodigiously. Start the cuttings now and you should have roots in two weeks, probably less, and quart-sized plants in another month. They'll then have a couple months to settle in before frost.

Given excellent drainage, I would think their chances of making it through the winter would be nearly as good as longer-established plants.

Steven

Thanks for the help. It gives me some hope. Last year's established plants didn't survived the winter soaking, it turned out they were too near the front of a bed where water collected - that won't happen again.