Yes, Plumeria can grow year-round in the warmest USDA zones.

The warmest USDA zones, which include zones 10 to 13, are characterized by minimum winter temperatures that range from 30°F (-1°C) and higher. In these zones, the climate is typically tropical or subtropical, making it suitable for plants like Plumeria are native to tropical regions.

Specifically:

• USDA Zone 10: Minimum winter temperatures of 30°F to 40°F (-1°C to 4.4°C). Plumeria can grow here, but there’s a risk of occasional frost, which might require some protective measures.
• USDA Zone 11: Minimum winter temperatures of 40°F to 50°F (4.4°C to 10°C). As mentioned in the previous response, Plumeria can grow quite comfortably without winter protection.
• USDA Zone 12: Minimum winter temperatures of 50°F to 60°F (10°C to 15.5°C). In this zone, Plumeria will thrive, growing robustly and producing flowers regularly.
• USDA Zone 13: Minimum temperatures above 60°F (15.5°C). This is an ideal climate for Plumeria, mimicking its natural tropical habitat.

Plumeria can remain in the ground year-round in these warmest zones, grow continuously, and flower regularly, provided they receive appropriate care. They do not need to be overwintered indoors, and there’s no need for dormancy. However, it’s essential to ensure they receive adequate water during dry periods and are planted in well-draining soil to prevent root rot.

For those growing Plumeria in these zones, it’s always beneficial to be aware of local microclimates, which sometimes differ from the broader USDA zone classifications. These microclimates can influence factors like temperature, humidity, and wind patterns.

You might want to check out resources available at PlumeriaCareGuide.com for detailed information on growing Plumeria in various conditions.