Oranges hold their multiple seeds in the center of the fruit flesh. As oranges ripen on the tree some fruit is dropped, lost to rot, or knocked down by weather. In addition, very bountiful harvests are often more than an owner can pick and consume and excess oranges will invariably fall to the ground when overripe. Fallen fruit rots and desiccates on the round eventually exposing its seeds to the soil, wind and animals.
Animal Assisted Scattering
Mammals and birds can open fallen fruits both consuming and scattering the seeds onto the soil. When they consume the fruit seeds can be transported in a fairly wide area and deposited through their waste. Deposited seeds can either germinate in place in moist soil or be blown or washed away by rains to yet other locations.
Human Assisted Cultivation & Sowing
Orange trees can readily be cultivated from seed in backyard garden and commercial growing operations. Growing oranges from seed is much less common than grafting however because when orange trees are grown from seeds they can take up to 20 years to produce fruit.