Question
I'm in San Antonio, TX, where the soil is mostly alkaline. It is underlain by a layer of chalk or caliche about 2"-12" down (mine is 12", having been built up in the past). I'm ambitious, and am planting a Japanese maple which I have nurtured for 2 yrs. in a pot without mishap (they don't normally do well here due to the heat). To plant, I'm using mostly humus to create the acidic soil I need. My question is: should I first install a layer of hard clay to slow down the leaching of the alkaline caliche? The planting area is isolated by stone decking, and is in sufficient shade. Thank you.

Answer
Hi Tom, I would first check your pH.  The maple should do well with a pH between 5.5 and 6.5.  Mix the humus with your existing soil and adjust the pH to within range.  Then plant your maple.  Check the pH periodically at different distances (1', 2', 3', etc# on all sides of the plant.  If your pH begins to rise, add a little copperas #iron sulfate# to bring it back down.  Japanese maples have very shallow roots, so I think keeping the soil surface pH within range will suffice.  
When the soil temperature gets high, Japanese maples slow transpiration in an effort to retain water.  High air temperatures and wind suck the moisture out of the foliage causing it to brown in mid to late summer.  Protecting it with some shade, and light colored mulch to reflect heat, will help it look better.  Good luck.  Jim