Plumeria, or frangipani (Plumeria rubra, P. obtusa and their hybrids and cultivars), produces heavy-petaled pinwheel-shaped tubular flowers that are prized for their exotic fragrance and for making leis. They need frost-free conditions -- U.S. Department of Agriculture Hardiness Zones 10 through 11 -- to grow in the ground, where they reach the size of small trees. Putting plumerias in containers and bringing them in for the winter allows them to grow in cold winter areas. Seed pods are only occasionally produced on Plumeria plants -- less often on plants grown indoors. Some cultivars are sterile and never produce pods. Pods contain seeds that grow into new plants.
The conspicuous pods begin to form after a flower is pollinated. In wild plumerias in Central America, sphinx moths -- also called hawk moths -- are the pollinators. In garden plants, plumerias can be self-fertile, pollinated by tiny insects called thrips -- and perhaps hummingbirds or butterflies -- or hand-pollinated by gardeners. Depending on the cultivar, seed pods resemble paired large slender horns or are shorter and oval.
Harvesting Seed Pods
It takes seed pods 9 to 10 months to ripen. They must remain on the plant during this time. If they are taken off earlier, the seeds do not mature. In some plumeria cultivars, the pods stay green right up to the time the seeds are ripe. In other cultivars, the pods turn brown or purple as time goes on. The color change doesn't mean they are ripe. The pod opens down one side when it is mature. Just before splitting open, the pod begins to shrivel and look drier on the outside.
To save the seeds, when you notice the pod beginning to dry slightly, cut the toe end from a panty hose leg and put it around the pod, fastening it to the stem end of the pod. You can also use a piece of organdy, tulle, or cheesecloth. The loosely woven material allows air circulation around the ripening pod but contains the papery-winged seeds so the wind doesn't blow them away when they are released. Seed pods contain anywhere from 20 to over 100 seeds, depending on the cultivar. You can also cut off the seed pod when you notice that it is ready to split open. Remove the stringy connection where the split is starting to form. Put the pod in a paper bag, where it will release the seeds.
The seeds are ready to be planted as soon as they come out of the seed pod, but you can put them in a paper bag for a couple of weeks to dry them out and help prevent mildew in planted seeds. Seeds store for up to two years in dry, cool conditions, but germination rates go down as seeds get older. Seeds are various colors. White seeds usually grow into white-flowered seedlings, and yellow seeds usually produce yellow-flowered plants. Pink, red, and multicolored seeds produce various colors in ranges of pinks, oranges, reds, and multicolored combinations.
Soak dry seeds overnight between moist thick paper towels. When you look at the seed after 24 hours have passed, the thick end of the seed opposite the papery end -- the plant embryo -- should be starting to swell. Put the seeds in a well-drained, sterile potting mix, embryo side down. Just barely cover the embryo and leave the papery part sticking up. Put each seed into its own small pot or use a nursery flat for multiple seeds and prick each seedling out when it is ready for transplanting. Keep the potting mix moist.
Seeds should germinate within two weeks. After the seed leaves -- called cotyledons -- emerge from the soil, the true leaves grow out between them after a few more days. Seedlings can be 6 inches tall after about 8 weeks. Transplant them into larger pots when they have three or four sets of true leaves. Put them into consecutively larger pots as they grow, fertilizing them monthly with a balanced fertilizer for the first year or two of life. A seedling usually flowers after about three years. Seedlings are unique and do not have exactly the same genetics as the parent plant.
Your Planting Articles
- University of Hawaii College of Tropical Agriculture & Human Resources: Plumeria
- Hawaiian Botanicals: Growing Plumeria
- Biotropica: Pollination by Deceit in a Mass-Flowering Tropical Tree Plumeria rubra L. (Apocynaceae)
- Valley of the Sun Plumeria Society: Growing Plumeria in Arizona -- Frequently Asked Questions
- Plumeria 101: Plumeria "Seed Pods"
- Plumeria Society of America: Plumeria
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