There is no need to fertilize until seedlings have their first true leaves (not cotyledons), but there is no harm, either. The strength of the solution depends on what type of fertilizer you're using and what the temperature is, but if temperatures are above 50*, you can start out by saturating the soil with a 1/4-1/2 strength solution. How often you fertilize after that depends on your watering habits, how fast the soil is, and what strength you fertilize at. If you're using a soil that drains freely so you can water copiously enough that a good amount of water exits the drain hole each time you water without risking root rot. You might try fertilizing at 1/2 strength every week or full strength every two weeks. There is no reason you cannot fertilize the plants on your list with a 3:1:2 ratio fertilizer like 24-8-16, 12-4-8, or 9-3-6 and expect good results. For more information & answers to most of your questions, you can follow the link below. Here is a link that might be useful: Fertilizing containers

First let me say there is a FAQ here about this question as well as many discussions about it the search will pull up for you. Feeding seedlings is a very debated topic, some do, many don't. Lots of variables to consider. The primary one being what nutrients are in your growing mix? You'll have to check the label for that info. If it contains added nutrients then nothing else is usually needed. Another variable is how long the plants have to go until transplanted out to the garden. If tomatoes were started at the usual 6-8 weeks before transplanting nothing may be needed. But if they have to sit around for 10-12 weeks before transplanting they will need feeding. There is no "what most use" fertilizer. There are 100's of choices and the choice is yours. While the plants are in containers most organic fertilizers will not work as there is no active soil food web to convert them to a useable form so liquid synthetics are used. If you feel you must use an organic only then one of the many fish emulsion/kelp blends or some sort of compost tea or worm tea are really your only good choices. And yes, they do smell. That is the nature of organic fertilizers. But if you do choose to feed them then wait until AFTER they have developed at least their first set of true leaves, use a liquid not a granular form, and dilute it to no stronger than 1/2 strength (many use 1/4 strength). Just as you wouldn't feed a newborn baby adult portions or steak and potatoes, the same holds true for seedlings. :) Dave

I start fertilizing mine when they go into four inch containers. I mix a half teaspoon of timed release into the soil as I pot them up. I use 18-6-12 with minors. Al

When you first repot a banana, esp a small one, wait at least a month before applying fertilizer. Give the roots some time to get established.