I still grow Yvonne's salvia but I start them from seeds indoors. Are you just setting out seeds now? I space my seedlings about 1.5 feet from each other, as I don't have a lot of room here. They grow best in full sun with a rich, damp soil. I have these growing off of my asclepias and Joe Pye area which is rich in moist compost, to give you an idea about the soil. Try not to have any other plants shade them out or they may not reach their height potential. They get about 5 feet tall and attract hummingbirds! I've planted some Y. salvia in less sunny areas and the plants got to about 3 foot.

Here's a pic of mine last year. Winter sown. 5 plants spaced about 8 inches apart. Got to be 5 feet tall. Full afternoon sun on the west side of h.ouse
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Duane