Bananas and plaintains (Musa spp.) are tropical herbs that resemble trees or palms. Wild species of bananas grow from seeds, while modern hybrids are bred for increased fruit flesh with infertile, tiny seeds. Once a plant stem flowers and sets fruit, it dies back, allowing young budding plants to rejuvenate from the fleshy rhizomes. Thus, the banana plant clump replaces itself and perpetuates for generations.
Within the fruit of a wild banana species will be tiny black seeds that are fertile. Once the banana drops to the moist, warm tropical soil, it will germinate. First a seed root emerges and then leaves sprout upwards to the light. Leaves emerge as a spear and unroll to reveal long, paddle-like leaves that are thick and waxy.
Growth and Maturation
Depending on banana species or variety, the stem of the plant may be short, like 3 to 5 feet, or as tall as 20 to 30 feet. There is no wood in the stem or "trunk" of the banana, thus it is merely a large herb. The top of the stem carries a canopy of leaves. Underground, the horizontal root-like stem, a rhizome, is expanding in size. In optimal growing conditions, this rhizome multiplies, creating an underground clump, from which new young banana plants emerge and grow.
Once ample soil moisture, humidity and heat are available, a pendent flowering cluster emerges from the tip of the stem among the lower leaf bases in the canopy. The flowers are small and slender and naturally are pollinated by hummingbirds, bats or insects. In wild banana species, fertilization of the flower ensures the formation of banana fruits. However, thousands of years of cultivation, breeding and selection of bananas has made most bananas today form fruits that lack ovaries, a process called parthenocarpy.
Wild species' ovaries, once fertilized after pollination, swell and ripe, each becoming the familiar long banana fruit in a cluster called a hand. Botanically, a banana fruit is called a berry. Within the fruits of wild bananas are small fertile seeds within the soft, tasteful flesh under the skin.
Modern sterile banana hybrids form from flowers regardless if a pollinator visits a flower. These selected bananas lack seed-making compartments and thus the ovary still swells and ripens to form a fleshy fruit, but there are no seeds made.
After a banana stem produces a flower it slowly dies, even if the flower is cut away or no fruits are produced. The leaves begin to yellow and the stem itself rots, eventually falling away from the clump to the ground. In wild species, the banana fruits with seeds would drop to the ground and possibly germinate.
Because of the clump-forming rhizomes, the banana plant is continually renewing itself by sending up new stems. As flowering/fruiting stems wane and die, young plants grow from the clump and perpetuate the banana plant for generations. In sterile modern banana hybrids that lack seeds, this rejuvenation is the means for new plants and stems to be propagated in the orchard.