Spring Planting of Perennials in Zone 6 Michigan: Hardening Off and Soil Preparation

Safe to Plant After Hardening Off

Yes — once night temperatures are consistently above 40°F (usually late April in SE Michigan), harden off 4-inch perennials for 7–10 days, then plant. Be ready to cover if frost threatens.

Hardening Off Schedule

• Days 1–3: 2 hrs shade, bring in at night.
• Days 4–6: 4–6 hrs part sun.
• Days 7–10: Full day outdoors, nights out if >40°F.

Soil Prep for New Beds (Per 10×10 ft)

• 4 bags topsoil
• 4 bags composted manure
• 2 bags sand
• 1 bag Milorganite (organic N)
• 2 bags cedar mulch
• 2 bags pellet gypsum (if clay)
• 1 bag sulfur

Rototill 12+ inches. For existing beds, work mix into top 6 inches around plants annually.

Why This Mix Works

Balances drainage, moisture retention, organic matter, and slow-release nutrients. Milorganite feeds soil biology without burning.