Planting Tropicals in Zone 9b (Contra Costa): Plumeria & Tiare Reality Check

You're in 94565 (Antioch/Pittsburg area), Zone 9b, heavy clay. Two potted plumerias, one new Tiare (Tahitian gardenia). Can they go in ground?

Plumeria: Species-Dependent

Some cultivars handle 9b; others need 10a+. Check Sunset Western Garden Book—your microclimate falls in Sunset Zones 14, 15, or 17 depending on elevation/fog. Sunset zones matter more than USDA here.

Tiare (Gardenia taitensis): Zone 10

USDA 10 = 30°F minimum. You're 9b (25–30°F). One hard freeze kills it. Unless you have a confirmed hardy selection, keep it potted and move indoors.

Clay Soil Fix for In-Ground Tropicals

• Mound planting: 12–18" raised bed of 50% native clay + 50% compost/pumice.
• Drainage is everything. Wet clay + winter = root rot.

Action Step

Visit a local nursery (not big box). Ask: "Have you had plumeria/Tiare survive in-ground here?" Their answer > any book.