Yes, you can propagate Plumeria (Frangipani) from mature seeds. In fact, mature seeds are the most suitable for successful propagation. Here’s how to propagate Plumeria from mature seeds:

1. Collect Mature Seeds: Wait for the Plumeria seedpod to fully mature and naturally split open. This indicates that the seeds inside are fully developed and ready for collection. Collect the mature seeds from the open seedpod.
2. Prepare the Planting Container: Select a small container or pot with good drainage. Fill it with a well-draining, sterile seed starting mix. Ensure the container is clean and free from any contaminants.
3. Plant the Seeds: Plant the mature Plumeria seeds about 1/2 to 1 inch (1.3 to 2.5 cm) deep in the soil mix. You can plant multiple seeds in the same pot, as not all seeds may germinate.
4. Provide Warmth: Plumeria seeds require warm temperatures for germination. Maintain a temperature of 75-85°F (24-29°C) to encourage germination. Using a heat mat can help maintain the ideal temperature.
5. Indirect Light: Place the container in a location with bright, indirect light. Avoid direct sunlight, as it can be too intense for seedlings.
6. Moisture: Keep the soil consistently moist but not waterlogged. Water the container gently whenever the top inch (2.5 cm) of soil feels dry. Avoid overwatering.
7. Germination Time: Plumeria seeds can take several weeks to months to germinate, so be patient. Monitor the container for signs of germination, which include the emergence of seedlings or tiny green shoots.
8. Transplanting: Once the seedlings have developed several sets of true leaves and are large enough to handle, they can be transplanted into individual pots or their final outdoor location.
9. Caring for Seedlings: Continue to care for the Plumeria seedlings by providing them with appropriate light, temperature, and moisture levels as they grow.
10. Fertilize Sparingly: After seedlings have established themselves, you can begin to fertilize them sparingly with a balanced, diluted liquid fertilizer.
11. Outdoor Placement: If you intend to plant the Plumeria seedlings outdoors, acclimate them gradually to direct sunlight over a period of about a week to prevent sunburn.

Propagation from mature seeds is a reliable method to grow Plumeria plants, and it allows you to collect seeds from existing Plumeria plants or from seedpods found in your garden. With the right care and conditions, you can successfully propagate Plumeria from mature seeds.