Plumerias (also called frangipani) are trees with fragrant tropical flowers. The trees have thick, fleshy branches that lose their leaves in winter. They are very frost tender, but you can grow them in your garden if you live in USDA climate zone 9 or higher (Houston to Honolulu). If you live in a colder climate, you can grow a plumeria in a large pot---it will do well and perhaps even flower in the summer, but you'll need to bring it indoors in the cooler months.
Caring for Plumeria Trees
Plant a young plumeria tree in well-drained soil that contains equal parts of sand, perlite and bark compost or peat moss, whether in the ground or in a pot. Potting soils designed for cactus are good for plumerias. Give it at least six hours of sun per day and plenty of water, but avoid planting it in an area with poor drainage where the roots will stay wet. Good ventilation is also important to plumeria health. Keep your plumeria in an area where the temperature never drops below 50 degrees F.
Fertilize your plumeria every other week from April until August with a high phosphorus, water-soluble plant food having an NPK ratio of 10-50-10. The low nitrogen content will cause more flowers to bloom. In late March and again in late April, feed your plumeria with Epsom salt, which is a form of magnesium that promotes green leaves.
Prune your plumeria during its dormant winter season using a tree saw or large loppers. Cut branches at an angle to prevent the cut from holding moisture. Don't worry if it drips a white, milky sap; this is called latex and it will soon stop. When you cut off a branch at any point, it will re-sprout two branches at the cut, which will result in more flowers.
Cut back on watering when your plumeria's leaves begin to drop and it stops flowering. If you have planted your plumeria in a pot, this is the time to bring it indoors.
Repot plumerias into larger pots every two years to give the root system plenty of room and to promote strong growth.
Plumerias are not often bothered by insect pests, but if your tree shows signs of damage from spider mites, white flies, thrips, scale or mealy bugs, spray your tree with a sharp stream of water to remove insects, and then spray insecticidal soap every other day until the insects are gone. For severe infestations, Maui Plumeria Gardens recommends Malathion or another appropriate chemical product designed for controlling the problem insect.