Gardenia fails to thrive - Knowledgebase Question

Name: sandy garigan
tucson, Ar
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Question by sgarigan
April 29, 2008
My gardenia has gone downhill ever since I planted it. Looks sickly, few leaves, has buds but they dont open, edges of leaves are brown, new growth is almost non existant. This is the second gardenia I planted in a whiskey barrel, gets morning sun, what can I do to get it to thrive??

Answer from NGA
April 29, 2008
There are some tricks to growing gardenias 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. ?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 Tucson. That's why it's best to grow gardenia in a container with a high quality, organic potting soil.

Plant the gardenia in the center of the container 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.

Best wishes with your gardenia!

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