By Dr. Leonard Perry, Horticulture Professor Emeritus, UVM
African violets are one of the easiest and most adaptable flowering houseplants to grow, as they do well in the conditions found in most homes. There are seven main cultural factors you should be aware of to ensure their success.
African violets that you buy are almost certainly hybrids, generally of one main species (Saintpaulia ionantha). The native habitat of this species, in the Tanga region of Tanzania in Africa, gives clues to its culture. The original species, introduced in 1893, was found growing there on mossy rocks and moist rock crevices in varying amounts of shade. This area is near the equator, and near sea level. What this means is that the temperatures vary some (basically 65 to 85 degrees) over the year, and the daylength pretty much stays the same. This area gets much rain, but it varies with season.
So how does this native habitat translate into the best culture for these plants in your home? First to note is the light, which shouldn’t be direct, or if so not for long. East windows often work well. South windows may provide too much light, north windows not enough. Not enough light and stems will stretch, forming an unsightly stem or “neck.”
Violets look great in windows, but also can be grown well under fluorescent light tubes. Place so that tops of plants are about 12 inches below tubes, and leave lights on for 12-16 hours a day. Regular cool white tubes work fine and are the least expensive, or mix with warm white. Replace tubes when they start to age, the ends turning dark.
The second factor is water and relative humidity. Taking a clue from their habitat, they like lots of water and humidity. But at the same time they grow in very airy spaces, not in heavy soil, so they don’t like overwatering. If anything, underwater. Overwatering is the most common reason African violets die. You can get water on the leaves, and in fact this is a good way to rinse dirt off the hairy leaves. Just don’t put cold or hot water on the leaves, and don’t get it on the center (crown). Make sure when watering that it is not icy cold, especially in winter, to avoid shocking the roots.
Humidity often is less than desirable, especially in northern climates, and in homes in winter. This can be raised by using a humidifier nearby, or placing plants on pebbles which are kept moist.
The next important factor is temperature, which should be in the range of their native habitat—65-85 degrees. Cooler and they won’t grow or bloom well, higher and leaves may burn and turn mushy. Avoid drafts near doors and heat vents which either can result in extremes, or in drying out leaves.
Fourth to consider is fertilizer and soil acidity, or pH. Most houseplant fertilizers will work, and there are some formulated just for violets. Use at the rate and timing according to label directions. Another key is to try and be consistent and not forget to fertilize, in order to get the best blooms.
Soil acidity shouldn’t be an issue, unless you have very acid or alkaline water, or are making your own potting mix. With 7.0 being neutral, the potting mix should be a slightly acid 6.5-7.0.
Soil texture is an important factor, as these plants naturally grow with much air reaching the roots. Generally avoid bagged mixes sold for houseplants, as these often have heavy black peat (decomposed peat moss) which holds too much water and too little air. A general bagged potting mix with peat moss, and vermiculite or perlite (equal parts of each) is ideal.
Sixth, consider pot size. Violets naturally grow on surfaces, so have shallow roots. This means they should have shallow pots, no deeper generally than four inches. They only grow to a certain size, varying with each violet. In general though, roots only grow about one-third the diameter of the leaves, so for a 9-inch wide plant, a maximum pot size should be three to four inches across. Use too big pots, and the roots won’t use all the water held there, and so may rot.
Finally, keep a watch for pests and disease. If violets are in a tight space, with little air movement, you may see powdery mildew develop on leaves– a white talc-appearing growth. Lowering humidity, and increasing air flow, may be all that is needed for control. This also will help control gray mold, a fuzzy gray growth on dying foliage and flowers. Avoid overwatering, and you should be able to avoid root rot diseases.
The main pests to watch for are thrips and mealybugs. Thrips are very small, the size of a printed dash, and feed on pollen. Blow on flowers and you may see them scurry. Mealybugs are small too, but usually seen as the white mealy masses covering eggs. An occasional gentle rinse with lukewarm and mild soapy water may help with these. Mealybugs may be dabbed with alcohol on a cotton swab. If you can’t control pests, it is best just to discard the plants.
Follow these tips and, with your success, you just may be inspired to seek out more plants of the hundreds available, with all kinds of flower colors and leaf shapes, and to expand into other fun activities such as starting plants from individual leaves. A good source of further information is the African Violet Society of America (www.avsa.org).
Photo courtesy of Wikimedia Commons