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Ask Dr. Hort: Reviving a gardenia, diagnosing problems with flax lily, avocado tree

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Published Jun. 9, 2012

Repot sad, sick gardenia

Q: I am enclosing a picture of my 3-year-old gardenia. The first year it was in a large pot. After it bloomed, I put it in the ground. Last year after it bloomed, the leaves started to turn yellow so I gave it a shot of Miracid. This caused a tremendous leaf drop. So the plant has just been sitting there looking like it does in the picture. (I did a little trimming of the dead wood.) Could it have something to do with the fact that the plant is about a foot from a trail filled with seashells? Would it be possible to put it in a large pot again now? H. Willeford

A: Your poor yellow gardenia, Gardenia angusta, has no real hope of survival in its current location because of the shell, which leads to a discussion of pH, which governs nutrient availability. Most plants prefer a soil pH of 5.5 to 6.5, and gardenia is happiest about 5.8. Shell is calcium carbonate (lime) which causes the pH to rise as it breaks down, tying up the micronutrients such as iron, manganese, zinc and others, causing major nutritional problems and a very sick plant. Repotting would be a grand idea. Be sure to water the soil thoroughly two to three days before digging to get a decent root ball. You still have a project slowly bringing the pH back down. Use your Miracid, 30-10-10, which has some micronutrients, weekly. Apply a low dose (1 teaspoon per gallon). The color should slowly begin to come back.

Flax lily, avocado tree are having issues

Q: I'm having trouble with my variegated flax and an avocado tree. The flax are 3 years old and started looking bad about three months ago. I have noticed that some of my neighbors' plants are looking bad, too. I have about 20 in my yard, and some of them are doing just fine. They were all planted at the same time.

The avocado was planted 20 years ago by my aunt and grown from a pit. I was told it would never fruit, but it does. The problem with the avocado besides the leaf drop is that the fruit rots on the tree and, if I pick it, it rots on the counter. I have been trying to figure this out for the four years I have had the house. There is no "ripening." Any suggestions on either of these troubles? Susan Weiland, Seminole

A: The pictures of the leaves of your flax lily, Dianella tasmanica 'Variegata,' exhibit rust fungus, a relatively new disease to attack the flax lily. Whenever we find a new non-native and different plant for ornamental landscapes, we have a tendency to overuse it, creating monocultures, and invariably a disease or insect will find it and have a field day. Hence rust has found the flax lily.

As with any fungus, eliminate overhead irrigation, as water spreads the disease. Clean out dead leaves and discard. Alternate systemic fungicides containing myclobutanyl, such as Spectracide Immunox Multipurpose Fungicide or Greenlight Fung-Away, with a protectant fungicide containing chlorothalonil, such as Ortho Garden Disease Control or Bonide Fung-onil, to reduce resistance and get ahead of the problem.

The pictures of your avocado, Persea americana, leaves and description of the fruit problems could be caused by one of many diseases that attack avocado. Anthracnose and Dothiorella fruit rot are likely candidates, but peruse, starting on Page 52, for a comprehensive list of avocado disease symptoms that match yours the best.