Plumeria seeds form when a flower is pollinated either by the wind (self-pollination) or by thrips, sphinx moth, tiny ants, or by humans. Once pollinated, plumeria flowers will fade and begin to grow into seed pods. Plumeria seed pods grow from flowers pollinated during the previous growing season. A single pod may contain from 25 to 60 seeds and usually grow in pairs. When the seed pod is growing you can wrap it loosely in cheesecloth to catch the seeds when it splits open. Do not wrap it so tightly that you block the circulation of fresh air.
Plumeria seed pods take about 9 months to mature. After they mature they will crack open and the seeds will be disbursed by the wind. If you harvest before they are ready, the seeds won’t have a chance to mature properly and most likely will not be viable.
Collecting Seed pods
Seed pods look like two long beans. They can be green or light brown to dark brown. Different cultivars will produce different looking and sizes. From the time they start growing to the end of their growth, they may reach up to 12 inches long or even longer. Seed pods will continue to grow over winter storage while their plumeria is in dormancy. So watch them during the winter, the growth is slower, but they could still open if they mature during winter storage.
When the pod starts to discolor and look like they are dying, they are getting ready to open. When you see the seam along the seed pod starts to crack, it’s time to cover. A netting material or stocking is good to cover the seed pod and capture the seeds. The netting will allow them to continue to receive water and sunlight through the openings. Place the netting or stocking over the seed pod giving it plenty of room to breathe and open fully.
Most plumeria seed pods open during the spring, but the seed pods will open all year long, depending on when the bloom was pollinated. Once they have opened, your cover will catch the seedlings. It is ok, to pick the pod if it has started cracking open. Place in a cool dry place and it will fully open in a few days. After it opens allow the seeds to dry out for a few days. Moisture can cause bacteria or fungus to grow.
After they have dried you may either store them in a dry dark place or plant the seeds. Some plumerias are great seed pod producers, some may only produce a few a year while others may never or very seldom produce seed pods. An example of Plumeria that rarely produces seed pods are Scott Pratt and George Brown. Some seeds will do better if you plant right away, an example is Dwarf Singapore Pink and P. Stenopetala. Seed Pods have been known to stay viable for 10 or more years, but the average is more like 3 years. Regardless the seeds germination rate will decrease over time.