A banana plant (Musa spp.) takes its time and is in no hurry to rush its luscious flower into maturity and fruit. The flowering stalk itself — the inflorescence — also takes its time, emerging anywhere from 10 to 18 months after the banana has either been planted or has broken ground from the underground rhizomes. But beware: If the bananas turn yellow on the stalk, they're already overripe.
A banana flower appears from 10 to 18 months after planting, and the flower then takes another 80 to 180 days before the bananas are ready to harvest, depending on the weather. Cold weather and shade prolong the process, and excessive heat will weaken the plant.
Banana Fruit Development
If you're hoping for a banana harvest and you're not just growing this tropical beauty as a landscape standout, you'll need to summon not only the sun, but its warmth, because banana fruit development occurs best when the temperatures are in the mid-80s Fahrenheit. Temperatures into the 90s can stress the plant and eventually scorch the leaves. On the cold side, growth slows when temperatures drop below 60 F, and stops completely at 50 F. Clearly, temperature impacts fruit development, which can be delayed considerably during cooler temperatures. Temperatures below 60 F, but above freezing, can also result in a complete failure of the flowering stalk to emerge or can produce fruit that doesn't ripen properly, is discolored or rots.
The amount of sunlight also matters. Bananas can tolerate as much as 50 percent shade, but it will delay fruit growth and development. Too much shade will stunt the plant's growth and harm the fruit's quality. Given the right conditions, however, the banana flower emerges from the stalk about 10 to 15 months after planting, and the time from flower to ready-to-harvest bananas is from 80 to 180 days.
Banana Fruit Harvest
The banana flowers that become fruit are female, with no need to be pollinated. Once the flower emerges, it quickly develops the "hands" that become the bananas, but these are tiny, hard and green. These baby fruit usually form in late summer, then need to winter-over before maturing. If you're lucky enough to enjoy weather that supports its over-wintering successfully, watch carefully as the fruit become larger and more rounded, usually in March to April. You'll see that each fruit will appear more smooth and lose its sharp, angular shape. When the fruit is plump but still green, it's time to harvest.
Home gardeners may want to wait until one hand just begins to turn yellow, indicating that the entire stalk is ready for harvest. If the fruit yellows fully, however, it may split on the stalk. Cut down the whole stalk and hang it somewhere cool and dry. Alternatively, harvest one hand at a time as it becomes ripe. If you choose this method, check the stalk daily, because rodents have been known to eat the insides of every banana while the stalk can appear untouched.
To hasten the ripening, cover a hand or the entire stalk with a plastic bag which captures the ethylene naturally produced by the fruit.