Gardenia browning leaves - Knowledgebase Question

belleville, Ne
Question by rcoachi
November 18, 2009
I just bought a gardenia family plant. It was very green and beautiful but now some of the leaves are getting brown spots. What is the problem?


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Answer from NGA
November 18, 2009

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To keep your gardenia healthy, here are some growing guidelines:
Gardenias thrive in 68-74 degrees Fahrenheit temperatures during the day, and 60 degrees Fahrenheit at night. These plants prefer full sun indoors, or at least bright light. They perform best if grown outdoors during the spring, summer and early fall, and taken indoors over the winter months.

High humidity is essential to gardenia care. Avoid misting the foliage, though, as leaf spot fungal problems will develop. The soil should be kept uniformly moist, but don't overwater. A loose, well-drained organic soil is recommended.

Fertilize monthly between April and November with an acid fertilizer.

Check regularly for insects and other pests such as aphids, mealybugs, spider mites, thrips and scales. There are two disease problems associated with gardenias:

Bacterial Leaf Spot (bacteria--Pseudomonas gardeniae, Xanthomonas campestris cv. Maculifolium-gardeniae) which causes small, round ovoid spots on young, tender leaves. As the spots enlarge, the center is at first pale yellow and later becomes reddish-brown surrounded by a yellow halo. Margins of the lesions are thickened and water-soaked in appearance. Spots may coalesce to form large, irregularly shaped spots. Severe infection may cause defoliation. To control, avoid overhead watering.

The second common problem is Leaf Spot (fungi--Cercospora spp., Phyllosticta spp.)
These fungi cause spots of various sizes on leaves throughout the year. Spots may be small, dark-brown necrotic areas surrounded by a yellow halo. In severe cases, premature leaf drop may occur. Control is obtained by spraying with a foliar fungicide.

You can cut off the affected leaves to keep the problem from spreading or you can use a fungicide on your plant to prevent the disease from spreading to new leaves.

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