African violets are among America's favorite flowering houseplants, according to Clemson University Extension specialists. Contrary to their reputation as finicky plants, African violets are surprisingly easy to grow. Because over-fertilization is a greater problem than under-fertilization for container plants, many indoor gardeners injure their houseplants by applying excessive amounts of strong synthetic fertilizers. Milder homemade fertilizers for African violets optimize their vigor and keep them blooming almost continuously.
Earthworm excrement, or castings, contain levels of nitrogen, phosphorus and potassium up to 11 times higher than levels present in ordinary garden soil. Plants must metabolize these essential N-P-K nutrients to sustain healthy growth. Castings contain other nutrients, found in earthworms' digestive secretions, that also contribute to the vitality of plants.
As an organic amendment, they are nontoxic and nonburning to plants. Earthworms in homemade vermicomposters digest certain kitchen scraps that reward gardeners with a free, odorless, organic fertilizer for African violets.
Phosphorus for Flowers
Flowering houseplants benefit from additional phosphorus. Bat guano is available commercially, packaged either as a high-nitrogen or a high-phosphorus source, depending on its processing method. The high-phosphorus source is an excellent choice for flowering plants.
Although it is expensive as a landscape fertilizer when applied over large areas, a little goes a long way with houseplants in small containers. A scant 3 tsp. of guano mixed in 1 gallon of water makes an excellent organic, homemade, liquid fertilizer for flowering plants.
Milk and Juice
As a specialist in soil fertility, Dr. Joseph R. Heckman knows the benefits of building soils to build healthy plants. According to his article in "Mother Earth News," Dr. Heckman uses only diluted milk and juice for fertilization. Before recycling milk and juice cartons, he rinses them with water and uses the liquid as houseplant fertilizer.
Milk contains nutritional elements of nitrogen, phosphorus and potassium, and juice packs an extra punch with its potassium benefit. This combination of nutrients provides a balanced houseplant fertilizer that is organic and homemade.
For optimal health, plants also need trace amounts of vitamins, minerals and amino acids. Seaweed contains these essential micronutrients, which are often deficient in other fertilizers, plus natural hormones that encourage plant growth. Mixing 1/2 tsp. of sea kelp meal in 1 gallon of water provides important nutrition to African violets.
A combination of bat guano and sea kelp, plus milk and juice residuals, provides a nutrient-rich, organic source of homemade fertilizer for African violets.
- New Mexico State University Cooperative Extension Service; Vermicomposting; George W. Dickerson; June 2001
- Clemson University Cooperative Extension; African Violet Diseases and Insect Pests; Nancy Doubrava, et al.; May 1999
- "Mother Earth News"; Easy Plant Fertilizer for Houseplants; Joseph R. Heckman, Ph.D.; August/September 2009
- Oklahoma Cooperative Extension Service; Vermicomposting – Composting With Worms; Sarah L. Kimball, et al.;
- Purdue University Cooperative Extension Service; African Violet Care; B. Rosie Lerner, et al.; March 2001
- Colorado State University Extension; CMG Garden Notes #234: Organic Fertilizers; Adrian Card, et al.
Victoria Lee Blackstone
Victoria Lee Blackstone is a horticulturist and a professional writer who has authored research-based scientific/technical papers, horticultural articles, and magazine and newspaper articles. After studying botany and microbiology at Clemson University, Blackstone was hired as a University of Georgia Master Gardener Coordinator. She is also a former mortgage acquisition specialist for Freddie Mac in Atlanta, GA.