Question
Good morning James.  I live in the Los Angeles area & the soil in my yard is
clay.  We dug large holes & mixed in good soil & peat moss before planting.  
I have several gardenias in my yard & the foliage on a few of them has
started to turn yellow this year.  They're full of unopened buds & the plants
are full of leaves but they're lime colored.  I've heard coffee/espresso
grounds boost acidity which is good for this type of plant.  Please advise.
Thank you,
Lisa

Answer
Hi Lisa, Before you adjust the pH, you should have it tested.  Most garden centers will do that quickly and for free, or you can buy inexpensive test kits.  Test the original soil, not the improved soil.  Since you'll probably be going to your garden center, take a sample of the plant with you. Nutrient, water and insect issues could all be at the root cause of poor color, so with your soil sample and foliage in hand, your nurseryman can give you a correct diagnosis.  Water is quite often the issue with gardenias.  I strongly suggest you go to an independent garden center, not a chain store.  Your local nurseryman is familiar with the local soil and problems you'll have.  He sees them everyday.  I'm not saying you won't find a qualified person in a chain store, but they are few and far between.  Jim