Boston fern, Nephrolepis exaltata, is a houseplant favored for its full, green foliage and its ease of care. Boston fern, like all houseplants, requires periodic fertilization. Attention to fern care and nutritional requirements will help the indoor gardener grow healthy, lush Boston fern.
Boston fern requires a well-draining potting medium. In the house or greenhouse, it prefers bright, filtered light. Boston fern requires consistently humid conditions, which is why it does well in bathrooms. Soil should be kept consistently moist, but never soggy.
Boston fern's nutritional requirements are relatively low. Because regular watering washes nutrients out of the soil, periodic fertilization is necessary with a houseplant fertilizer. As with all houseplants, avoid overfertilizing, as well as overwatering, which lead to a buildup of mineral salts in the soil.
Use a houseplant fertilizer, diluted to half strength. Houseplant fertilizers are typically balanced (have equal amounts of nitrogen (N), phosphorus (P) and potassium (K)). N-P-K ratios will resemble 20-20-20 or 10-10-10 in a balanced fertilizer. Houseplant fertilizers usually come in concentrated liquids or water-soluble granules. Both are mixed with water to dilute.
Prepare the fertilizer according to label directions, diluting to half the recommended strength for houseplants. Wet the potting medium thoroughly until the liquid runs out of the bottom, tipping the pot and saucer gently to remove excess liquid. Fertilize Boston fern from April to September, when it is actively growing.
In the garden, grow Boston fern in partial shade. A few hours of morning or evening sun is adequate. Garden soils that are rich in compost often provide adequate nutrition for Boston fern, so fertilization is needed more sparingly than for those grown indoors.