In hypogeal germination, cotyledons remain inside the seed shell, beneath the ground and non-photosynthetic, while in epigeal germination, the cotyledons expand to split the seed coat, allowing the sprout to push them above the ground where they become photosynthetic, according to Reference.com. Epigeal germination allows the young plants to begin providing food quickly as the cotyledons have little food stored to provide for their needs.
Epigeal germination has both advantages and disadvantages. It allows plants to produce smaller seeds than those that sprout underground. However, pushing the cotyledon above ground makes the young plant more susceptible to frost and the grazing of animals. These plants generally overcome these barriers by producing a large number of seeds to give plant reproduction a statistical advantage. Their germination process requires external nutrients, so they prefer nutrient-rich soil. They do best in areas where there is adequate sunshine for photosynthesis to take place. Germinating above ground increases the plant success rate, making it particularly adaptable to areas where it is important to establish the plant quickly, such as the river borders of the Amazon, where flooding is a problem. However, once the initial first phase ends, the plant develops more slowly than a plant that uses hypogeal germination.
Hypogeal plants require less sunlight to germinate and are more suited for areas such as forest interiors where sunlight is limited. While slower to establish themselves, these plants grow faster than epigeal plants once they germinate.