Answer: Gardenias like slightly acidic soils so you can either fertilize with an acidified food (Miracle-Gro, for instance), or mulch around the bottom of the plant with peat moss. Aside from that, your hardy gardenia will grow slowing into a mounding shrub and look (and smell) fantastic when it is in bloom.
Spots on rose leaves can indicate a disease called black spot. To manage black spot, 1) Rake and discard all fallen leaves because they are the main source of spores in the spring. 2) Also prune and discard any obviously infected canes. 3) Avoid wetting the foliage especially during dark cloudy days. 3) Grow plants in an open sunny location to promote rapid drying of the foliage. 4) Do not plant in dense plantings and avoid windbreaks to allow good air circulation. 5) Roses vary in their resistance to this disease. Use resistant varieties for low maintenance plantings. 6) Removing infected leaves as they arise early in the season may help to retard the rate of disease spread. 7) Several fungicides are registered for control of black spot (Captan, Funginex, Daconil, etc.). Because of the waxy nature of rose leaves, a spreader added to the spray will give better coverage.
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