Hi Kelly, Generally, the things to look out for when a gardenia starts to fail out of the blue are potential problems you might not be able to see on the surface. I may have a few suggestions, so forgive me in advance for the longwindedness :) How's the drainage in the general area where the shrubs are planted? Gardenias like very good drainage for sure, without too much fluctuation in humidity and air flow throughout the plant. You can also try to supplement trace minerals, particularly magnesium. Epsom salts are good for this, as the sulfur also acidifies the soil. It's not a quick-fix-silver-bullet type of thing, because it can take weeks or months to see improvement. Are you for certain the soil is also acidic enough? You mentioned being planted underneath an oak tree, but oak leaves might not be enough. An acidic fertilizer (like for camellias and azaleas/rhododendron) being applied might improve acidity, but it's always best to test your soil pH to be sure. Also check to see if there might be tiny pests, particularly if there's any webbing on the undersides of leaves. It could be spidermites or some other juice-sucking critter. The gardenia may also benefit from removing any of those oak leaves around it and replacing with a bark-type mulch. Those leaves can harbor pesky problems and create too much fluctuation in moisture, temperature, humidity, etc. Even the best cared for gardenia can have some yellowing leaves. It happens to mine sometimes, particularly a month or two before they start to bloom (they bloom here in May). My theory as to why is that the lack of acidity, even when slight, prevents the plants' roots from properly absorbing the phosphates in the soil to create buds and the yellowing leaves are just the plants reaction. You may also have to give the gardenia a year or two longer to really establish itself. They're known to have a long-term (a year or two sometimes) ugly phase when transplanted from one environment to a completely different one. Hopefully some of these things will help. Good luck! :)

I had the same problem. I got some epsom salts from bunnings & spread it around the base of the plant & watered it in. Now they are great. They need magnesium. Hope this helps

He looks like toast to me. Sorry. Usually browning like this only occurs when something cataclysmic occurs: goes bone dry, bad fungus, complete root rot... Which occurred I can't tell. If you scratch the bark, first on an outer branch, see if it's green under the bark or brownish. If yes, try the trunk: if that's brown, there's no recovery possible.

It could also be the soil you used to repot it! Last year I bought some Miracle Grow Moisture guard potting soil (which I had used successfully many times before) but this time EVERYTHING I repotted with it died within a week or two. EVERYTHING!!! I've been gardening, indoors and out, for over 40 years and can't remember the last time I lost a plant when repotting! When I went to Scott's/Miracle Gro website to complain I saw SO MANY experienced gardeners with the exact same complaints I had and some insolent, smart aleck customer no-service dweeb would always "reply" saying there was nothing wrong with their product so it had to be "user error". Many of the folks complaining had as much - or more - experience as I had! It was absolutely insulting! I used to believe in their products but won't chance it again. Who knows when there might be another contaminated batch?!? Only good thing is that the patch of invasive English ivy I dumped all the bad soil out onto DIED! (And we all know how hard that stuff is to kill!). Scott's/Miracle Gro lost a good LOOOONG TIME customer because they couldn't admit they might have sent out a bad batch! I know I'm not the only experienced gardener who won't be using them again!