Native to Australia, callistemon grows well in USDA zones 9 to 12. It requires full access to sunlight and moist soil. When fully grown, it can be 30 feet tall and 15 feet wide. It has bright red brushes as flowers, consisting of long spikes. It also has broad leaves with pointed tips and grows well from seed. These seeds come in woody capsules and germinate in two to three weeks.
Collect callistemon seeds from the mature seed capsules, which open when ripe. Depending on the particular species of callistemon, the seeds may remain on the capsules indefinitely or may be released by the capsules when mature. If the plant retains the seeds indefinitely, place the capsules in a warm, open container for two to three days until they release the seeds. If the plant releases seeds annually, collect the capsules when the first ones start to open.
Fill a pot that has holes in the bottom with seedling soil and place the pot in a shallow container of water. The water in the container will move up the soil to reach the callistemon seeds and keep them moist.
Spread callistemon seeds on top of the seedling soil and slightly press them into the surface of the soil.
Sprinkle a thin layer of sieved sand onto the seeds, so that the sand just barely covers the seeds.
Refill the container of water when it runs low to keep the seeds moist until they finish germinating in 14 to 30 days.
You can also cultivate callistemon plants from cuttings to retain the desirable characteristics of the parent plant.