Watering
Hibiscus like "even" watering. Don't let your hibiscus get too dry or stay too wet. If dried out for too long, the plant can drop its leaves or even go into shock and die, despite renewed watering. If overwatered, especially in pots, fungal disease can destroy the root system, or the soil can pack and deprive the roots of needed oxygen. In short, Do NOT water plants if they are still wet.
In summer, when the plants are in active growth, they require more water. While not all cultivars enjoy the same amount of water or tolerate the same amount of dryness, hibiscus in general like being well watered, especially in hot weather. Even so, hibiscus do not like to be continually wet, as this promotes fungal disease and packs the soil, robbing it of vital oxygen. Do not leave them sitting in saucers full of water for too long. If possible, water in the mornings and let the plants dry out over the course of the day.
During cooler periods of the year, water more sparingly. In winter, when the plants are NOT in active growth, water only when the plant is dry. Cool moist conditions are ideal for fungal diseases, and one must be careful NOT to create those conditions.
Occassionaly, plants will lose all their leaves. This is either a reaction to stress or the natural process of renewing its foliage for a different season. When plants are without leaves, there is relatively little transpiration and it may be days before they need watering again. Overwatering now can cause "root rot."