First we laid out a 120 foot X 120 area...has a 20 foot grass area going north to south, 8 foot grass areas going east to west with a large circular area in the middle....the grass area divide it into 4 planting areas...each planting area has a 2 foot wide bed around it to be planted in daylilies planted by colors and forms...inside each daylily bed is a 3 foot wide path line with monkey grass...each of the four sections will be laid out in a different style...one section has an X path dividing it into 4 V areas....This is where I need help so far only one section of the "V" area has plants ordered...64 lavender plants..also have order 25 rhubarb plants but need suggestion for other plants that can be managed in this historic type garden.....v

Have you visited Mount Vernon Gardens website? Unfortunately I didn't find plants in a list form, but many specific ones are mentioned in the paragraphs.

This article about the restoration of the original garden would probably be enlightening.

The pic at this site looks like it's very formal in places. I'm not familiar enough with it to understand which part you're emulating, sorry if that's not relevant.

Not at all a fan of P. Allen Smith, but he visited and there's a video here that shows a lot of plants up close and views of the gardens.