I apologize for this delayed reply to your gardening question and hope it is still helpful to you.
Yes you can plant grass plugs in July or August too. You'll just need to water them frequently for the first month or so to help them establish in the heat. There is not good St. Augustine type of seed. I don't think you'll find seed anywhere and if you do it won't make the best type for a lawn and is not recommended.
Thanks for the question. Best wishes for a wonderful gardening season. Please stop in again soon!
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