Answer: I love the fragrance of those purple hardenbergia blooms! When leaves completely dry out, the problem is often salt burn. This is common in our area with low rainfall, alkaline soil and water high in salts. Browning usually occurs on the old leaves first. This excess salt accumulates in the leaf edges, where it kills the tissue and the leaf dries out and turns brown. It's important to water deeply, slowly and infrequently. At least once a month, water deeply enough to "leach" or push salts below the root zone. Frequent, light "sprinklings" allow salts to accumulate in the top layers of soil, where the roots are, which is bad news.
Similar symptoms occur when too much fertilizer has been applied. Because of the sudden change in your Hardenbergia, I wonder if this isn't the problem. (Note that even if you didn't apply fertilizer directly to this plant, it could have absorbed it from elsewhere, such as turf, which is often heavily fertilized with nitrogen.)
When fertilizing, moisten the soil well before and after application. Follow package directions exactly. (A little bit more is never better!) Fertilize just before the growing season begins (late Feb.-early Mar) and lightly again in the fall (mid to late Sept). Fertilizing during the hot weather isn't a good idea because the potential for burn is increased. I hope this answers your question.
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