Many people overlook the importance of fertilising indoor plants. That’s unfortunate because feeding is essential to keeping healthy, beautiful plants. Unlike an outdoor garden, where nature provides rain and plants can send new roots searching for food, the nutrients available to a houseplant are strictly limited by the amount of dirt in the pot and whatever else you give it.
Think of fertiliser as the second half of your potting soil. When your potting soil is fresh, your plants won’t need much, if any, fertiliser. This is especially true of modern, fortified potting soils, which often have fertiliser and other enhancements mixed in. But after about two months, the plant will have consumed the nutrients in the soil, so you’ll have to fertilise if you want continued, healthy growth.
As a word of warning, always follow the label instructions on your fertiliser. Too much fertiliser can kill a plant or scorch its leaves, and there are environmental concerns to fertiliser overuse as these nutrient-rich solutions find their way into groundwater supplies.
Different types of fertiliser
Fertilisers come in several different varieties: liquid, sticks and tablets, and granular and slow-release forms. Of these, the two best suited for indoor use are liquid and slow-release fertilisers. Sticks and pills seem convenient, but they don’t distribute nutrients very well through soil and, once you’ve shoved a fertiliser stick into your pot, you have no control over its release. Granular fertilisers are really designed for outdoor use.
All general-purpose fertilisers contain the basic macronutrients that plants need to grow, including nitrogen, phosphorous and potash. Each macronutrient has a special function:
Specialty fertilisers, such as African violet fertilisers, contain optimised proportions of these nutrients for particular kinds of plants. In addition to these macronutrients, better quality fertilisers also contain micronutrients such as boron, magnesium and manganese that will encourage healthier growth.