Answer: Alyogyne huegelii 'Santa Cruz' hails from Australia where temperatures are hotter and humidity lower than in your garden. Because of this, the stems tend to elongate due to weather conditions. You can keep your plant a little denser with early spring pruning. Wherever you prune you should get two new flowering stems. The yellowing leaves are those being shed in favor of healthy new leaves. In a few weeks the shrub will develop new foliage to replace that which was lost. Try pruning your hibiscus back and see if that doesn't help it thicken up a bit. Best wishes with your landscape.
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