|leaves on my gardenia are curling and i have brown tips on the leaves. the ground shows there is plenty of water|
|gardenia successfully here in the desert southwest.
Most importantly, choose a gardenia that is best adapted to hot, dry conditions. Gardenia jasminoides 'Veitchii' is the preferred variety to grow. It has smaller leaves and flowers than the better known G. grandiflora, but will produce a profusion of fragrant double-white flowers in the spring. 'Veitchii Improved' is also recommended and has slightly larger flowers and in greater numbers than 'Vetchii'.
One of the keys to success with gardenias is the soil. They grow best in acidic, well-drained, highly organic soil - all the things we don't have here in the desert. That's why it's best to grow gardenia in a container with a high quality, organic potting soil.
If your bent on growing your gardenia in the ground, I suggest doing it in a container. Dig a hole in the soil big enough to accommodate a large pot. Fill be bottom of the hole with a twelve inch layer of gravel for drainage. Then set a large clay pot in the hole. The rim of the pot should set just above the surrounding soil. Fill the container with a high quality potting soil, leaving two inches at the top for a layer of ground wood mulch. I prefer mixing my own soil, using a combination of one part peat moss, one part perlite, and one part vermiculite. These ingredients are available at garden supply stores.
Plant the gardenia in the center of the pot with the top of the root ball flush with the top of the potting soil. Scuff up the roots on the outside of the root ball to encourage them to grow out into the surrounding soil. Finally, add the layer of ground wood mulch or fine bark chips over the soil to improve moisture retention.
Proper fertilization is also important for gardenias. Most gardenias grow and flower well with applications of slow release or water soluble fertilizers with moderate levels nitrogen, phosphorous and potassium. Suggested fertilizer ratios are 3:1:2 or 3:1:3 (e.g. 15-5-10 or 15-5-15). If you can't find these specific fertilizers, use something with a similar ratio of nutrients. I prefer the general purpose, slow release fertilizers. Most last for 3 or more months. The first application should be made in March, and the second in July. If your using a liquid plant food, begin applying in March and continue fertilizing every two or three weeks through September.
Frequently plants will become yellow due to a deficiency of one or more micro nutrients, usually iron. This can be corrected with the addition of a chelated form of iron, most often sold in a liquid form in the garden centers. Remember to apply "chelated" iron; other forms of iron just won't work. Make the application of iron on an as-needed basis directly to the soil around the gardenia.
Yellowing of gardenia leaves can be caused by things other than nutritional deficiencies. Potential causes include; insufficient light, over watering, poor drainage, and too low soil temperatures. Several investigations have indicated that a soil temperature below 70 degrees causes leaf yellowing. Inconsistent watering can also cause leaf yellowing and a browning of the leaf tip and edges. Some leaf yellowing of older leaves is natural and will occur in the winter prior to new spring growth.
One of the biggest complaints of gardenia growers is bud drop and bloom failure. It is commonly caused by excessively hot, dry weather when the plant cannot absorb water fast enough to replace that lost by transpiration. Keeping the gardenia in an area sheltered from hot afternoon sun and winds will help. Placing potted gardenias among other potted plants will also help by increasing humidity in the surrounding air. During hot weather it is important to keep the soil consistently moist. This may require daily watering, or even twice-daily for plants setting on sunny patios.
Finally, to keep gardenias shapely and encourage new growth and flowering prune lightly when flowering has finished in the spring. Do not prune in late summer or fall as this will reduce blooming the following spring.