Nick C. grows all sorts of bananas in Gwinnett County, northwest of Atlanta. see Banana Care
He has specific tips on fertilizing bananas.
“I like to start slow with the chemical fertilizer in the spring about 1-2 weeks after planting in my banana beds, so the roots can establish a little. After that I increase the dosage every two weeks about 25%-35% until about a month before first frost in the fall. As the plant grows bigger, it can handle more fertilizer. The increase in the dosage depends on which banana cultivar I’m fertilizing – some can take a lot and some are more sensitive to it. You can tell when to back off a little by the way the newer leaves start to bend/twist. My goal is to have banana fruits so I’m less interested in the leaves looking really nice and more interested in pushing the growth as fast as possible to have fruit before first frost. They still look nice, but sometimes the leaves tear when coming out of the psuedostem because they’re growing so fast.
My general rule across the board is to use about a 1/2 cup of 10-10-10 with about an additional 25% supplement of 0-0-62 Muriate of Potash for a banana plant that is approx 4-6 feet tall. if you have a 2-3 foot banana plant, just divide by 2. If I know a certain cultivar can handle more/less, I make the adjustments to the dosage. After a few doses, you’ll get more confident in how much to feed them. Usually by mid-summer, I’m piling it on them.
The dosage also needs to take into account how many banana pups (babies) the mother has and the size of the pups. Let’s say you have a 10 foot tall banana plant with 2 pups about 4-5 feet tall, you could nearly double the dosage. That would be about 1 cup of 10-10-10 with 25% 0-0-62 Muriate of Potash supplement. The size of the pup’s psuedostem is usually not as big as the mother so that’s why its not tripled. I’m sure you could triple it but the banana plant will probably look like a corkscrew pointing up at the sky!
One thing to keep in mind is that you almost have to try to kill them with too much fertilizer to actually kill them. But too much fertilizer can stop them from growing for weeks to a month which would be a killer for any hopes of fruit. Each week of growth is critical in Georgia’s short banana growing season!
The above fertilizer dosages are for edible cultivars. I know a lot of folks in Georgia have Musa Basjoo bananas (probably one of the most cold-hardy in the world). This is an ornamental banana that doesn’t really need as much potassium as the edible ones. The Musa Basjoo can take almost double the dosage of 10-10-10. I’d say take the above dosage and multiply it by 1.5-1.8.
I hope this helps but it could be rather confusing when starting out. Just start out by giving the bananas a standard dose the first 1-2 times and then let them tell you how much they want moving forward.