A botanical illustration of purple giant hyssop, pink wild bergamot, blue asters, and grass.

1. Back Row (Tallest Plants): Giant Hyssop (Agastache foeniculum) — 1–2 plants (purple spikes) Wild Bergamot (Monarda fistulosa) — 1–2 plants (pink/purple) Little Bluestem Grass (Schizachyrium scoparium) — 1 plant (blue-green foliage, red in fall) Spacing: 18–24 inches between plants for tall flowers. Total plants: 3–5 plants. --- 2. Middle Row (Medium Height Plants): Smooth Blue Aster (Symphyotrichum laeve) Total Plant Quantities (for a Full Garden Look): Tall plants (Giant Hyssop, Wild Bergamot, Little Bluestem Grass): 3–5 plants Medium plants (Blue Aster, Prairie Coneflower, Yarrow, June Grass): 5–7 plants Front plants (Prairie Smoke, Blue Grama Grass): 3–4 plants See more