According to HCG, Red Happiness gets to 28-32 inches tall.
http://www.highcountrygardens.... I don't know how tall the two of mine are, as I've been pinching them lately, so they might be shorter than their height.
I been growing two A. Desert Solstice (another HCG intro) for a few years. They state the height is 32-36 inches tall.
http://www.highcountrygardens.... I never thought to measure them and I don't think they're on the high end of 36 inches, but then I've planted them too close together than they should be.
A. Ava, another HCG intro
http://www.highcountrygardens.... They've stated, in their printed catalog, to plant it in compost enriched garden loam. They've stated it takes 2 or 3 growing seasons for it to reach its mature size of 48-60 inches tall x 24 inches. You can always pinch it back if it gets too tall. Wonderful and beautiful Agastache that keeps its coloring long into the season. I should grow more of it. I lost the 2 - 3 plants I had in the ground after a few years and I think I didn't have enough compost in the soil.
Here's a pic I took (of the one I got earlier this year) on August 1 of this year in the container tub next to the back of the house on the patio and a cropped pic of it. I made sure I added plenty of the Vermont Compost Plus container booster to the soil.
http://www.gardeners.com/buy/o...
Early next year they should have more Agastaches available than they do now. Get on their website and add your email address so you'll know firsthand when they have sales, info, new intros, etc.... and request their printed catalog.