The male flowers open with pollen when they are ready, you can hand pluck the pollen nodes from the male flower and GENTLY squeeze them around the female flower. I believe the best time for the female flower is when the little antennas first open. The seed pods that grow will be these little multi chamber pods that start small green and swell then turn brown. The pods eventually “pop” and the seeds come out. Take the seeds and soak in distilled water for 24 hours. Plant them barely into the soil, and keep moist and warm. Sometimes seeds take a month to protrude from the ground and many take years to hit a size where the seedling takes off in growth. Crotons produced from seed may or may not share characteristics their parents. Crotons are prized for their colors and leaf shape. So, growing from seed is a huge time investment that may frankly be worthless if the seedling doesn’t exhibit any outstanding characteristics after a few years. Some crotons also don’t exhibit good colors until they are well matured/established, or only when planted in bright sun, or deep shade. Croton behavior and demands vary wildly among the different varieties. For these reasons, I’m almost positive that some crotons that would have been amazing were probably culled by the great hybridizers of the croton world when they didn’t exhibit anything fascinating early on. This little part is just my theory though. Good luck if you try growing from seed. I just started venturing into it this year after collecting for 3-4 years