I think you can use it anytime. I fertilize my seedling as I do my other trees. Good luck!

Thanks, then I will start fertilizing them. And how often do you fertilize?

Or maybe anybody else who can give me some more information? What is your fertilizing schedule?

Be careful fertilizing seedlings as it is very easy to burn their tender roots. Many places do not recommend it as they should be able to pull the nutrients out of properly amended soil. If you used a decent potting soil to start, they should have sufficient for their needs for some time. If you want, experiment with one seedling first and see how it reacts. Fertilizer pellets will take awhile to breakdown, so be patient!

Start fertilizing when the first true leaves appear. (The first two leaves are cotyledons, not true leaves.)

I always start fertilizing seedlings with half dose of recommended amount. The recommended dosage should be written on your fertilizer container.

Would you guys recommend FP or Osmocote for young seedlings?