Hibiscus trees are known for their dark foliage and colourful blooms, and they are a showcase in any outdoor garden or indoor display. Like other healthy flowering plants, hibiscus trees need fertiliser to stay hardy and keep blooming, but these plants require specific nutrition.
The hibiscus tree is a hardy tropical plant that is part of the Malvaceae family. It grows best indoors when it's away from its natural warm climate. The many different varieties produce hundreds of stunning colours of single and double blooms that range in size from 2 inches to 10-12 inches. Some varieties grow to a foot tall while others grow to 5- or 6-feet tall, and those in the natural climate grow to over 15 feet high. Known as the national flower of Malaysia, it's also become one of America's favourite blooms, according to the American Hibiscus Society.
Hibiscus plants prefer a slightly acidic soil that has a pH of 6 to 7. The plants need several hours of full sunlight a day to produce blooms and maintain them. Without the sunlit window, the hibiscus tree will grow and produce only foliage. The plants should be watered when the top 2 inches of the soil is dry or about twice a week. They should not be left to stand in water as the roots will rot.
The best fertilisers are water soluble ones that can be spread evenly into the soil or sprayed onto the leaves for foliage feeding. This solution should become part of the regular watering regime so that the tree can get a constant feeding of nutrients to continue to bloom. Read the ingredient labels on your fertiliser package to ensure that trace minerals such as copper, zinc, iron and manganese are included. The front label will list the three main ingredients by numbers, representing the percentages of nitrogen, phosphorous and potassium. Ideally, the reading should be 17-5-24 or similar.
Nitrogen aids the plants in their metabolic processes and is necessary in healthy growth. Too little nitrogen will stop the plant from flourishing and producing healthy blooms, and too much can harm the plant with "fertiliser burn," which causes the leaf edges to turn brown. Hibiscus trees need a mid-range level of nitrogen. The label should read 15-20.
Contrary to most flowering plants, hibiscus trees do not like much phosphorous. Too much will cause the plant to wilt and become stunted, and the leaves to turn yellow and fall off. This happens because the phosphorous prevents the roots from feeding the rest of the plant, and the plant slowly begins to starve and die. Special 'bloom booster' fertilisers are extremely high in phosphorous and should not be applied to hibiscus trees. The number on the label should be low, about 5-7.
High doses of potassium are necessary for healthy plant growth and metabolism. It assists in photosynthesis which enables the plant to create sugars for foods through sunlight and water. This food builds the healthy plant, its woody stems, deep green foliage and colourful blooms, and it strengthens the plant's ability to fight disease. Much of the supply of potassium is used up in the blooms, so it's crucial that it's replaced on a regular basis. The levels should read at least 24.