The answer to all three is .........nothing :-) Seriously, if you have halfway decent soil to begn with - and you certainly should if you have a hope of growing JM's - then seldom is any fertilizing required. And this is true of most woody landscape plants (trees and shrubs), so you can include your crapes and hydrangeas in the same grouping.

In more than 30 years of gardening I can't remember a single instance of my needing to fertilize a JM growing in the ground. Container plants are another matter entirely. But I do recommend using a good organic mulch around the tree, both to conserve soil moisture and moderate soil temps and to contribute to organic matter replacement in the soil. Since I grow my maples in mixed planting beds, I tend to use a compost as mulch rather than a wood-based product but those will work well also.

Thanks for your response, gardengal. I believe the soil is in good shape; I followed your advice in preparing the planting holes last fall and using only the original soil, mulching well afterwards. The soil seems to have provided a great home for the maples; although the leaves are tiny, they grab your attention immediately.
I mulched the JMs with pine bark nuggets last fall. With an abundance of pine needles from fall and spring, I'm considering replacing the nuggets with the pine needles, applying a thin layer of nuggets on top of the needles. (Will do this strictly for the sake of economy; pine needles are free; the bark, not so much.) Is there any reason to think that this combined use of nuggets and needles would be harmful? Would it still provide a free flow of water and air?
gary

Either - even both - is fine :-) Just make sure you don't apply too thickly and keep well away from the trunk.

As always, your advice is appreciated.