se or to order in transplants is largely an economic decision and should be made carefully.
Leaves for propagation should be selected from well maintained stock plants that are recently mature and have good green color. A good rule of thumb is a size between 1¼- to 1¾-inches long. The petiole is trimmed to ½-inch long and inserted into the medium so the leaves do not touch each other. Leaves are generally arranged in rows in 14" × 24" nursery flats at 56 to 72 leaves per flat depending on the cultivar. Many different propagation media have been used by growers including peat, peat and sand, vermiculite, peat and vermiculite, or the general potting medium.
Rooting of the leaves occurs in about two weeks and plantlets (offsets) emerge from the base of the petiole in about 6-8 weeks from sticking. At this time, the mother leaf is removed to prevent shading the newly emerged plantlets. Some growers will remove about half of the mother leaf and then remove the remainder several weeks later based on the idea that the mother leaf continues to contribute to the growth of the plantlets. Light fertilization of the young plants can begin at about the time of mother leaf removal. The total propagation time for leaf flats is 14 to 16 weeks depending on the cultivar and time of the year.
Plantlets are removed from leaf flats and separated into single crowns when they have about three to five mature leaves. They are then graded into small, medium, or large groupings. The process of grading by size may be done by hand or mechanically based on weight. Plantlets can then be rooted in plug flats (72 or 84 cells/flat), 14" × 24" nursery flats, or directly in finished pots. The latter method is often used for 2½- or 3-inch finish pots. For ease of transplanting, plug flats work best for transplanting to 4-inch pots. Once the plantlets are stuck in flats, about 6 weeks will be required to reach a transplantable size. This time can vary depending on growing condition and size grade. The small grade often requires about one week longer to mature in the plug flat and the large grade about one week less than the medium grade.
Potting and Finishing
The majority of African Violets are potted and finished in 4-inch pots, though 4½- and 5-inch pots are not uncommon. During potting, care should be taken not to plant the plugs too deep and that patented cultivars are properly labeled. Once potted, the plants can be maintained on the bench, pot-to-pot, for 5 to 6 weeks. Optimum light, temperature, and other cultural practices are important at this stage for a vigorous uniform crop. When flower buds begin to poke up through the leaf canopy, plants can be placed at a final spacing of four pots per square foot on capillary or ebb-and-flow benches. African Violets are usually shipped when 5 blooms are open depending on the desire of the market. This will usually occur 5 to 6 weeks after spacing. The total production time from leaf cutting to a finished 4-inch pot is 32 to 36 weeks depending on the time of year and geographic location.
The schedule in Figure 1 is a generalization. Individual stages may require more or less time depending on the cultivar, time of the year, and geographic location.
Figure 1. Production stages and timing for scheduling African Violets in 4-inch pots.
The most important consideration for a disease-free crop lies with sanitation of all pots, flats, benches, medium, and any other articles coming in contact with the plants. General greenhouse cleanliness is a must! This is especially true where "crown rot" (Pythium/Phytophthora) is concerned. Other factors in disease prevention are: obtaining healthy transplants, keeping plants growing vigorously, the correct environment, and carrying-out production stages on time. Fungicide treatments come and go, but it is easier and less expensive to prevent disease problems rather than cure them. Powdery mildew can be a problem during changeable weather. This can be controlled by burning sulfur and modifying the environment to keep the foliage dry. Botrytis is best controlled by reducing the hu