I was never a gardenia fan, for two reasons.
First, I was impressed by my mother's sad story of her own mother's funeral. She was six years old and had never seen a dead person. Her mother was in the casket, her small stillborn baby at her side. Gardenias filled the room, and their heavy scent mingled with the tears and oppressive heat of that day.
"I can't stand the smell of gardenias," my mother often said. "They make me sick to my stomach."
So I never bought a gardenia, out of respect for my mother.
Second, gardenias have a reputation for dramatically dropping dead without cause. So I wasn't interested in planting a gardenia. There are too many other plants to choose from with better reviews.
Then one day my neighbor Betty gave me a cutting from her own healthy specimen, which grew and bloomed reliably every year. I didn't want to offend her, so I took the cutting and put it in a jar of water, thinking I would do my duty until it died. The plant responded by quickly sprouting roots. Okay. Now I had to plant it. I put it at the sunny edge of the woodland garden, a place my mother was unlikely to visit when she came to my house. I didn't expect much from it, and it would not grieve me when it passed away.
That was less than a decade ago, and now my gardenia is about eight feet tall and wide. It has glossy green leaves and lovely white flowers, and the single shrub fills the woodland with its sweet aroma when it blooms every year. I have decided not to be burdened with my mother's memories, and I look forward to the wonderful olfactory experience each June.
Gardenias are also known by the common name 'Cape Jasmine.' They are as southern as iced tea, screened porches and lightning bugs. They like heat and high humidity and will grow in full sun to partial shade. They shouldn't be planted near the foundation of a house or next to a concrete walk, as lime can leach into the soil and harm these acid-loving plants. Ideally, they should get about one inch of rain each week. Gardenias like well-drained, moist soil, and it's a good idea to put an organic mulch at the base to conserve moisture. I use pine straw, which also helps to acidify the soil. I deadhead my shrub after blooming, because this will encourage more flower production. I also don't like the look of the aging flowers, which turn an ugly brown and cling to the branches.
The key to a happy gardenia is to plant it in the right environment. I think it is hard to create the perfect climate artificially, and this probably accounts for its finicky reputation. A stressed gardenia is prone to disease and poor growth.
Don't think, however, that yellow leaves necessarily mean the plant is sick. Gardenias don't loose their leaves during winter and are considered evergreen. But as spring turns toward summer, up to a third of the old leaves will turn bright yellow before they fall. 
I did not love my gardenia from the beginning, but the little cutting my neighbor gave me has won my heart. I now know why this plant has endeared generations of southerners, and I am happy to have one thriving in my garden.