Never fertilize at planting time. There's enough stress already on the plants regardless of planting time and fertilizing only adds to that factor. Just make sure the plants have adequate water - that's the most important factor.

I believe that most times we become too focused on the need to fertilize. We can thank Miracle Gro and others of their ilk for that!! As long as you have moderately decent soil, there is really no need to fertilize established inground plantings unless they show obvious signs of deficiencies. And most of the time you can circumvent those by routinely applying an organic mulch. Containerized plants are a bit different but even with my extensive JM collection - all in containers - I only fertilize once a season in early spring with a CRF like Osmocote. No fertilizing after August 1 for containerized plants.

As to the advisability of fall fertilizing for inground plants, it is a great time IF (and only if) any fertilizing is required. Roots are in an active growth pattern at that time and are able to absorb nutrients very efficiently. You just want to avoid any high N ferts that would encourage rapid growth that could be damaged by winter cold. In fact, waiting until after a good frost is probably best if you choose this timing

Thanks, gardengal.
If I've interpreted correctly, no fertilizing the new trees at planting time.
As far as those that were planted in previous seasons, apply, at most, a modest amount. Was thinking about a quick-release fertilizer high in phosphorous and low in nitrogen and potassium. Or use an organic source such as bone meal. Is this right?

Back to those recently purchased trees: I'm keeping them in their original containers (looks like a peat/bark/grit mix in the containers) for the next 6-7 weeks before planting in the ground. Is there never a situation where they should be fed while in their containers? My biggest concern is the 'Waterfall'. This cultivar is the only one I've ever had problems with in past years: it went belly-up after two years. Vertrees had recommended that it should get full sun despite it being green in color and a laceleaf at that. The one I purchased recently has its leader cut off (probably why I got it at such a good price) and has some browning at the tips of a few leaves. Keep it moderately damp, a bit of morning sun exposure and no feeding during this time. Correct?

Of course containerized maples should be fertilized - ALL containerized plants need supplemental fertilization - but just not this late in the season. The plant will be going dormant before too much longer anyway and the need for any fertilization will be nil. Besides, it is very likely still carrying some nutrients in the form of CRF's applied by the grower or nursery. If you were going to keep these in a container, then I'd suggest you apply some sort of fert in spring.

Fertilizing is NOT a requirement for inground plantings. Most trees and shrubs are able to obtain all the nutrients they need from their surrounding soil and this is almost certainly the case if you employ an organic mulch on a routine basis. Only fertilize if you know there is a need, either from a soil test or if the plants display obvious deficiencies. I gardened for over 30 years with a very diverse and complex garden and never fertilized anything but container plantings. I did apply a good compost mulch to all planting beds at least once a year - that took care of any ongoing nutrient needs.

Excellent advice gardenGal.
I have 3 potted JM's, Orangeola, Shishi Yatsabusa and Kamagata. I like to give them a low nitrogen fert DynaGro "Grow" (7-9-5) and DynaGro ProTeKt (0-0-3) at 1/5 strenth every 2 weeks until around the first day of Autumn.
My reasoning...mostly OCD.

My trees are 5-8 years old, and I do not use CRF. What are your thoughts on my fert regimen?

Your choice of fert is always your choice, spaceman!! I like the CRF's because I have too many containers and watering them is enough of a chore, let alone needing to fertilize them routinely throughout the summer. Personally, I really like the Dyna Gro products and I use the Grow myself for all my seasonal containers and houseplants. Now and again the maples and conifers will get a dose of it too if I think about it :-))

If your trees are doing well on that regimen, I'd see no reason to change.