I agree 20" is tight on the 'Hameln.' Their fountain tops would be intertwined at that spacing. Little Bluestem, on the other hand, is more upright, and has a smaller spread.

I don't know what look you're after, buy I'd probably go 2' on the Little Bluestem and 3' on the 'Hameln.' In ideal conditions, with mature plants, the tops of each would either just be touching or just short of touching.

Thanks very much Donn. I'll do as you suggest.

I was confused because I read such a wide range for both spread: Hameln (18-30"), Little Bluestem (18-24"), and suggested spacing: Hameln (20-30"), Little Bluestem (18-36").

I know it's not an exact science but wanted to get perspective from a real person who grows grasses--so thanks.