Allow the fruit from the parent tree to completely ripen before harvesting its seeds. Pick the unblemished fruit from the tree. Place the fruit in a warm, dry location until it splits open, revealing the seeds.
Remove the seeds from the fruit. Wash the seeds to remove all residue from the fruit. Put the seeds in a warm place to dry.
Sand the seeds lightly with sandpaper or nick the side of each seed with a sharp knife. Place the seeds in a bowl and cover with hot water. Allow the seeds to soak overnight, until the seeds swell and double in size. If the seeds don’t swell, remove from the water and nick the hard outer shell again. Return the seeds to the bowl and add more hot water.
Remove the seeds from the water and treat with a fungicide according to the manufacturer’s directions. The champaca is prone to fungal infections, which will kill the young seedlings.
Place 4-inch pots on a tray. Fill the bottom third of each pot with a high-quality acidic potting soil suitable for azaleas or rhododendrons. Add sterile seed-starting mix to the top two thirds of the pot. Water thoroughly to ensure that the soil is moist throughout the pot.
Insert one seed into each pot and barely cover with seed-starting mix. Cover the pots with plastic wrap and place in a warm location.
Check the soil every two to three days to ensure that it is still moist. Mist with a spray bottle if the soil begins to dry out, then replace the plastic wrap to maintain a consistent moisture level.
Maintain a constant temperature of 80 to 85 degrees Fahrenheit until the seeds germinate, between one and five weeks. Champaca has a relatively low germination rate, between 40 and 50 percent.
Place the seedlings in a warm, sheltered location in the garden or sun porch that receives morning sun. Champaca begins life as a second-story tree, receiving only dappled light in their native habitat. While under ideal conditions in the tropics a champaca tree may grow to 150 feet tall, in the United States it generally only reaches 20 to 25 feet tall.
Water the tree when the soil is dry to the touch. Fertilize biweekly with a liquid 10-10-10 fertilizer according to the manufacturer’s directions.
Plant the champaca in the garden in the spring, after all chance of frost is past. A south-facing wall that receives morning sun and some afternoon dappled shade provides a warm microclimate suitable for this tropical tree. Select a well-draining location that is sheltered from the wind and hot afternoon sun.
Give the seedling plenty of water during its first couple of years of growth. After that water regularly in the summer when the tree is actively growing. Fertilize in the early spring with a balanced fertilizer according to the manufacturer’s directions.
Prune only to shape the tree and remove dead branches.
Monitor the tree for aphids. Knock the aphids off with a strong stream of water. If there is a severe infestation, use an insecticidal soap to kill the aphids.