I am having the same problem and my research kept pointing to not enough water. Our area is hot and dry, but they have afternoon sun. From what I read they like loamy, acid soil and humidity. In your case I am wondering if you should water more often, but not as much each time. In hot dry areas, they recommended they might need watering 1 or 2 times a day. I def. need to water mine more often and will give it a try.
Apparently fertilizing regularly and properly is important too.

I think both of you need to read this: Suicidal Gardenia Thread.

Ryan

If planted in well drained soil you don't need to worry about over watering. They do need plenty of water and of course regular fertilizing with an acid type fertilizer. Mine does well in 3 to 4 hours sun per day. Al

Keep an eye on the leaves. Don't worry about the flowers. If you think the plant is in danger, I would pull it and put it in a pot of Kellog's azalea soil. Then water well when the soil drys out in the top few inches. I find that If I can learn the water schedule when the plant is still in a pot, them all I have to worry about is the sun exposure and getting the soil just right. I lost a number of expensive gardenias to soil that wasn't acid enough. I saved some plants too by potting them and keeping a careful eye on them until they stabilized. The best I have done is with potted plants in a controlled soil under a lath or in bright shade under a tree. A few hours of earliest morning sun seems to work fine too. Don't wait until the leaves are too far gone to act. I would say that if you are not letting the top part of the soil dry out in between waterings, you may be overwatering. I have my plants in the ground on slightly raised mounds to help me in this respect.

I think I just realized why Home Depot and Lowes sells things like Gardenias. People keep killingthem, but it is something hard to resist, so we have to buy more. They are like brownies. I know yhry are bad for me...but sometimes they are too tempting to resist after denying myself for a long time. It seems as though Everyone I talk to has a mother or grandmother who grew grew beautiful Gardenias, however I killed several. Right now the 2 I transplanted at the ecge of the Mexican lime tree are doing pretty well, but not getting decent flowers yet. I am watering them regularly and they are definately doing beter than any other location I had them. They get morning sun and afternoon shade.

my landloard has one on his porch, it gets afternoon sun, it wasn't blooming and the leaves were turning yellow. He pruned it back and only waters it when it get semi-dry. I told him it likes acid soil so we put some oak leaves in the pot for mulch, fed it with MircleGro all purpose food and he gives it his left over StarBucks coffee diluted w/water and its doing good. Leaves are green and buds are comming out. I also spray it with a solution of 1-2 tsp. each of baby shampoo, epsom salt, proxcide, water if it looks like its getting mites or whitfly. Hope this helps. He's had the plant for about 5 yrs.

My advice is to check the soil a few days after one of the drippers has watered your gardenia. Dig down and figure out how deep the water is going. Since this is a new installation, it's important to keep the plant "comfortable" with the right amount of water while it sends out new roots. Unfortunately, it's hard to say whether or not you are watering too much or not enough because part of it depends on the soil--is it like clay, like sand, like loam? Does it drain quickly or slowly, is the plant mulched? I think if the first five or six inches are dry then it's probably not getting enough water. If the soil is quite moist, maybe it's getting too much and you could increase the length of time between waterings. However, until your shrub gets established it may not perform as well as you would like.

I have a gardenia (Veitchii) that gets full sun in the afternoon but it's finally starting to behave; my problem is that I underwater. I've noticed, though, that when I do get around to watering, many green buds will suddenly bloom. In the past it rarely bloomed, mostly brown buds and brown, partially-opened flowers. Even when I watered, most would drop and I would get one or two blooms. I attribute this to my plant "settling in" and becoming established because now it's a much better bloomer. Five years later...!!!

melle sacto has given a very good description of learning the requirements of the gardenia. If you are using a drip to water your gardenia it will still require your observation to see that it is sufficient. The cone of soil moisture from a dripper will vary a LOT with the texture of the soil. Al

Yours lived for five years?
I thought they were annuals!

LOL--and still growing :-)