May – June: 
ISN’T  IT TOO LATE TO PLANT TREES????
( “What’s you talkin’ about Willis?”)
BALDERDASH !!!!

There is only one definite time that it is not advisable to plant Jms and that is in mid winter and even then in the south that may be doable ..
Spring planting can be done anywhere .. it is IMHO to always buy trees that have leafed out and  have survived the winter from whence they came .  The only caveat is it not be too early for northern areas. But for the south it is a whole other matter. Spring for south can come early and some folks think they need to have trees in the ground in what most of us consider winter or very early spring ( Feb & early March) . Some local extension services even suggest not planting after mid March .. This of course is hog wash… as long as you are careful and acclimate your trees you can do so way in to summer without much problem and it’s a no-brainer in April and May. And remember if you get trees in Feb or March from warmer areas they will most likely already be leafed out  as most nursery’s don’t have cold storage . That can be disaster if they hit a sub freezing area on their way to your more moderate climate !! For Southerners being a bit too anxious can be just as much a faux pas / disaster as for a northerner.

Summer is a descent time to plant jms .. yes they must be given a bit more attention and carefully introduced to the sun but I have done it with little or no problems. For many northern JM’sters it may even be preferable …Even if you are in the deep south you can simply pot them out put in shade , enjoy them and plant in fall.. I don’t ship during really hot periods but there are always breaks and with today weather maps and forecasting it is a breeze to make sure it travels safely during a more moderate period. Remember we are only two to three days from all our shipping areas not a week like the west coast nurseries .. In addition we pack in such a way they should be fine for 10 days in all but the most torrid weather.
BUT if you are a “northern worry wort” , not living in the south,  you too  can containerize all jms in pots all summer long even  in the hottest weather …Enjoy their beauty all summer and then plant them in the fall or bring in the garage for winter and plant them out the following spring .. This sometimes is of great advantage, since you can move them around and see what spot looks best to you, as well as which spot they like  best  and be 100% sure you have the perfect sweet spot for them to be planted out in fall or the next spring. A win win situation. Even for non “worry warts” this method can often save having to move a tree or put up with a bad decision .. it allows you to make better choices.
Fall is also a great time to plant Jms but for northern growers it can be a bit more dicey .. ..but I have found the difference in spring and fall planting for northerners  is minimal with larger trees . For northeners I do suggest keeping all one gallon trees trees potted and kept inside over the winter in an unheated garage.. .
If any of the Japanese Maple Mr, Ms or Mrs ” know it all’s ” and ” blow hard’s ” say otherwise, just remember the word BALDERDASH !!!