Hopefully Shoe doesn't mind since many of his answers were in open forum and I AM giving HIM the credit since he's the guru of these babies...just figured if I kept his helpful hints he wouldn't have repeat himself every year - sweetheart that he is:
MAY 2007 – GARDENIA CARE by horseshoe
What I normally tell my customers at the Mkt is to plant them where they get a bit of sun (the more sun, the more flowers) but yet in an area where the Winter winds won't blow on them, thereby dessicating them. In the past I've heavily mulched them to protect their roots but those that were being wind-whipped it didn't really help..the winds just pulled all the moisture out of them.
If you haven't already planted I'd recommend you water them in with some fish emulsion rather than feed them the Hollytone right away. That will get them off to a good start but yet not chance any burn of new roots that will be developing soon. After 10 days or so then lightly broadcast your Hollytone on the surface of the soil and scratch it in. (There is also a "Miracle Gro for Azalea, Camellia, Rhododendron" food that is excellent for gardenias if you can't find the Hollytone.)
I wouldn't mulch right away, if you do it'll only block the sun from warming the soil and contribute to "cold feet", which is not what the newly-planted gardenias like. They need warm soil to encourage root growth as well as nutrient uptake.
As for the Epsom's salts, I use it sparingly, usually as a foliar spray to encourage flowering. However, if you are planning on using the sulphur to lower your pH plus using Epsom's directly in the soil they'll be competing with each other to do their job (Epsom's will tend to raise the pH slightly, thus my recommendation to use it more as a foliar spray, and do it when the plants are well on their way).
As for Hollytone vs Miracle Gro-etc...I've used both and have good results when using them at certain stages (and reasons).
Miracle Gro products are derived from "chemical ingredients" (and yes 'all things are chemical') but in this case I'm referring to the nutrients being offered are derived from Ammonium phosphate, Urea, Potassium phosphate, Chloride, Boric acid, etc (plus a few others). Those are readily available to the plant but don't tend to really contribute to the soil growth the plant is living in.
On the other hand, Hollytone (for acid lovers) offer its nutrients from more "natural" sources; Dehydrated manure, Feather meal, Crab meal, cocoa meal, corn gluten, cottonseed meal, dried blood, sunflower meal, kelp meal, alfalfa meal, greensand, etc. Those are sources that contribute to the life of the soil and tend to offer an ongoing/slower release nutrition. So....for me....
I used the Miracle Gro for a quick pick-me-up when plants are stressed or looking a bit sickly. The M-Gro can be applied foliarly and will immediately get to work helping the plant through stress and back to good health. I use the Hollytone for a more long-term feeding.
Lastly, remember, Miracle-Gro products have to be used every 7-14 days whereas the Hollytone is used only twice a year.
Hollytone works well without having to use the sulfur unless your soil is very alkaline, then you might want to incorporate some sulfur at planting time. However, as far as I know, more often than not alkaline soils tend to be further west than you; perhaps you might be in a special pocket that has alkaline soil?
Methinks you should pick up a pH analyzer (about $12 or so) and then you'll know. And of course, you can always incorporate sphagnum peat into your planting hole which will give you a lower pH.
I've not used Messenger and am one of those that don't see the need for it. There are quite a few threads on DG with the supposed pros and cons though.
As for ironite/adding iron to the soil or plants...if you use the Miracle Gro that has iron in it already so you should save yourself the expense of purchasing iron separately. Most soils are not iron-deficient but rather tend to bind up the availability of iron to the plant so people "short cut" it by applying liquid/chelated iron directly to the plant. Too much lime in the soil, raising the pH to a more alkaline state, will make the iron in the soil unavailable. For long term availability of iron using plenty of manure, dried blood, or compost would be your best bet.
Should you be losing your plants in the summertime then it could be due to a pH problem (they like a bit of acid pH) or could also be wet feet. They love a good bit of moisture but prefer good drainage. Not planting them too deeply will help, that way you can mound dirt/soil up and have it slope away from the main trunk, diverting water to the outer reaches.
Oh yeah, regarding sun exposure, yes, more sun more flowers USUALLY. The exception would be if you're in an extremely hot area where the plants would benefit from the shade during the hottest months of Summer. I have a gardenia on the northwest side of the house, gets very little direct sun but yet flowers like crazy most years. The only other placement I'd suggest is to put them where the Winter winds won't blow on them as it tends to dessicate them
