Answer: Your African Iris should be dug and divided this fall. When you unearth the rhizomes, break or cut them apart into smaller sections and then replant them. They'll bloom better when they're not so crowded.
It sounds as though your gardenia had a heavy infestation of aphids. When they feed they exude a sweet substance called honeydew. This turns into sooty mold. Now that you've controlled the aphids, the sooty mold will weather off the leaves. If the oldest leaves are yellowing and dropping off, it's a natural progression. Plants lose their oldest leaves and then develop healthy new leaves. This is the time of year that gardenias drop their oldest leaves. Fertilizing will help green things up. I'm not sure your plant needed a systemic spray. Between the fertilizing and the elimination of aphids, it should perk right up. Hope so!
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