Overwintering Rosemary in SW Pennsylvania (Zone 6b): Hardy Varieties & Protection

Standard rosemary dies in Zone 6b winters. The solution: plant hardy cultivars with site-specific protection — not bringing indoors (powdery mildew trap).

Choose the Right Genetics

Cultivar	Hardiness	Flavor	Growth
'Arp'	Zone 6 (–10°F)	Piney, strong	Upright, 4–5'
'Hill Hardy' / 'Hardy Hill'	Zone 6 (–10°F)	Best culinary, balanced	Dense, 3–4'
'Salem'	Zone 6b	Good	Compact

95% of herb farmers choose 'Hill Hardy' for flavor.

Planting for Survival

• Site: South-facing wall (radiant heat), excellent drainage, protected from NW winds
• Soil: 50% native, 30% coarse sand, 20% compost. pH 6–7. Raised bed ideal.
• Timing: Plant by early September for root establishment.
• Mulch: 4–6" straw/leaves after ground freezes. Remove gradually in spring.

Winter Protection System

1. Wire cage (chicken wire) around plant — 12" gap
2. Fill cage with dry leaves/straw
3. Wrap cage with burlap or frost cloth (not plastic — traps moisture)
4. Top open for snow insulation (snow = best insulator)

What NOT to Do

• Bring indoors — low light + dry heat = mildew death spiral
• Plastic wrap — fungal incubator
• Heavy pruning after August — removes protective growth
• Wet feet — ensure drainage

If You Must Pot

Use 'Arp' in 15-gal pot. Sink pot in ground summer. Move to unheated garage (30–40°F) winter. Water monthly. Return outdoors April.

With 'Hill Hardy' + wall microclimate + wire/leaf/burlap system, 15-year plants are common in Pittsburgh area.