Gabe15

Just as a general point of perspective, more fertilizer will not inherently result in faster growth. It's not like dumping more fuel on a fire. At best, adequate fertilizer will support the growth and allow the plant to maintain fast growth if the optimum environmental conditions are met which are the real drivers of fast growth, namely plenty of sun and warmth.

You don't need much fertilizer, especially if you're not trying to continually harvest large bunches of fruit, but you do need as much sun and warmth as you can get. In the Northern hemisphere, planting bananas on the south side of a brightly colored building with full sun all or most of the day can really get things cranking, some light and heat is reflected off the building during the day, and during cooler nights the building and foundation can maintain warmer localized temperatures. Match that with plenty of water, mulch and adequate fertilizer, and you can hope to maximize growth rate.

As others have stated, too much fertilizer is a real thing, especially when using high-potency synthetic fertilizers, and without the other important environmental conditions met more fertilizer will do nothing. I also fully agree with others that having a healthy soil high in organic matter and active with microorganisms is an important foundation that will greatly aid in growth and allow the plant to utilize whatever extra fertility you do decide to add.

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Growing bananas in Colorado, Washington, Hawaii since 2004. Commercial banana farmer, 200+ varieties.