Answer: Hibiscus may yellow for a number of reasons. Whent hey are in active growth, the soil should be kept evenly moist, not sopping wet. They appreciate a water soluble fertilizer according to the label instructions (over feeding is not better than underfeeding). If kept from year to year, they should be repotted as needed to accommodate growth and/or rootpruned and tip pruned to maintain size. Also check for pests such as whitefly or little webs under the leaves (most pests can be treated with insecticidal soap applied according to the label instructions). Finally, hibiscus may shed some foliage as a shock response to being moved either from indoors to outdoors or from the greenhouse to the patio. When bringing them outdoors after a winter inside it is a good idea to move them gradually so they can acclimate to the real sunshine. When bringing a plant home from the store, there is not much you can do except optimize care as outlined above. To keep a plant blooming, you need to provide maximum light during the winter, so the plant stays in active growth. Pruning will delay blooming, as will cool temperatures, lack of light, and/or lack of fertility or poor watering practices. I hope this helps you trouble shoot.
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