These instructions are sent with the plant gift
For best results place your Gardenia near a window or skylight or in an enclosed porch or conservatory. Indirect light is best and the cooler the room is, the longer the flowers will last. Gardenia’s can be quite sensitive to temperature, ideally you are aiming for 18-21˚C in the day time and 15-16˚C at night but as long you protect your plant from extreme summer heat and very cold temperatures it will reward you with evergreen foliage and heady scented blooms.
Gardenias are thirsty plants, the warmer the room, the more they will drink. Water thoroughly from the top several times a week and let the excess drain away. The compost should be damp to the touch at all times, if the weather is very warm or you are going to be away for a few days you can stand it in a shallow saucer of water although try not to do this too often as this could lead to root rot. Gardenias are acid lovers and will prefer rain to tap water, after a few weeks you may want to feed your plant using an ericaceous feed (i.e. a feed suitable for Rhododendrons or Azaleas would be fine).
These plants have just been repotted but next spring your Gardenia should be repotted again using ericaceous or acidic soil. To keep your plant looking good, remove any spent flowers to encourage new growth.
Gardenias are tropical plants and do like a humid atmosphere and plenty of water. Drooping or flower drop is usually due to lack of water so give your plant a good drink.
Finally a build up of Chlorine can cause yellowing leaves, if this occurs, swap over to rainwater and your plant should soon recover.