Primary propagation of billia is typically achieved via seed sowing. Key factors include ensuring adequate light exposure, maintaining a consistent temperature suitable for germination, and using well-draining soil. Special considerations might involve scarification or stratification to enhance germination rates. It's a moderately difficult species to propagate, as seeds may have dormancy issues. For propagation, collect ripe seeds, scarify if necessary, sow them in well-draining soil, keep soil moist and in a warm, shaded area, and wait for germination, which might require patience.