Saintpaulia ionantha spp. (African violets) are one of the most popular flowering plants in America. Given proper care, African violets will flower abundantly and continuously throughout the year. Unfortunately, many of todays' offices and interiorscape settings do not provide the optimum light levels needed by most cultivars for maximum bloom production.

Thousands of cultivars of African violets exist, and vary greatly in their ability to bloom under interior light levels. Plants typically stop flowering after one month under light intensities of 150 ft-c or less because carbohydrate production is insufficient to provide for flower initiation and development. With time, some cultivars acclimatize to lower light levels and bloom again. Interiorscapers typically circumvent low light level problems with foliage plants by rehabilitating plants in greenhouses for a time, alternating time spent in the interiorscape with time spent in the greenhouse.

This experiment was conducted to (1) examine the blooming ability of 21 cultivars of African violets receiving 150 ft-c, 12 hours daily; (2) to test the effect of a lowered ratio of P and K, in comparison to N, in fertilizer source on bloom production; and (3) determine rehabilitation time when cultivars were moved from 150 ft-c to greenhouses with 1500 ft-c. Twenty-one cultivars of mature, blooming African violets growing in 4 inch plastic pots were obtained from commercial growers. The cultivars tested were assigned numbers after all recorded data was examined in order to simplify discussion of results obtained from this experiment. Plants (1) Mia, (2) Kimi, (3) 330, (4) Mary Anne, (5) 24B, (6) 128, (7) Bobbie and (11) Angie, are popular commercial cultivars, while plants (8) Hickerson #1, (9) Hickerson #7, (10) Hickerson #12, (12) Hickerson #9, (13) Hickerson #10, (14) Hickerson #13, (15) Hickerson #2, (16) Hickerson #3, (17) Hickerson #4, (18) Hickerson #5, (19) Hickerson #6, (20) Hickerson #8 and (21) Hickerson #11 are less commonly known to the floriculture industry. All cultivars tested are described in Table 2. Plants were fertilized with either 1 gram 19-6-12 per pot every 3 months or 1.36 grams 14-14-14 per pot every 3 months. More 14-14-14 was used to compensate for the lower percentage of N in 14-14-14 compared to 19-6-12, so that all pots received the same amount of N. All plants were placed in rooms simulating an interiorscape environment. Light levels were maintained at 150 ft-c for 12 hours daily and temperatures ranged from 71°F to 78°F. Watering was performed once per week.

After 3 months indoors, half of each cultivar was moved to greenhouses with maximum light levels of 1500 ft-c and temperatures ranging from 65°F to 90°F, with plants watered as needed. This was done to determine rehabilitation potential of the different cultivars tested after 3 months under 150 ft-c. The remaining plant material was maintained in the rooms. Blooms per pot were counted once per month until experiment was terminated on Dec 14.

Fertilizer source had no effect on bloom production with all cultivars displaying steadily decreasing bloom production for 3 months after placement in rooms. For cultivars 1 through 9, bloom count in rooms leveled off after 3 months then held steady or slightly increased over time (Table 1). These same cultivars made a more rapid recovery when placed in the greenhouse. Cultivars 10 through 14 stopped, or almost stopped bloom production in the rooms after 2 months, but showed signs of rehabilitation after 2 months in the greenhouse. Of 21 cultivars tested, 7 (cultivars numbered 15 through 21) showed no signs of bloom production after 2 months in 150 ft-c rooms and displayed no signs of rehabilitation when placed back in 1500 ft-c greenhouses for three months. Therefore, these 7 cultivars are excluded from Table 1.

These results show that light intensity is critical for bloom production of African violets, a high ratio of phosphorus and/or potassium to nitrogen is not necessary, and cultivar selection is important.

¹Professor, Plant Physiology and Center Director and Professor (retired 7/96), respectively, Central Florida Research and Education Center, 2807 Binion Road, Apopka, FL 32703-8504
²Technical Assistant.

1. Anderson, H. 1984. The effects of temperature, frequency of watering composition of fertilizer and peat type on Saintpaulia. Tidsskrift Plant. 88:183-191.

2. Conover, C. A. and R. T. Poole. 1981. Light acclimatization of African violet. HortScience 16:92-93.

3. Milde, H. 1980. Saintpaulias, a comparison of slow-release fertilizers. Vergleich von Langzeitdungung 80:486-488.

4. Poole, R. T. and C. A. Conover. Response of African violets to fertilizer source and rate. HortScience 21:454-455.

^ZOsmocote 19-6-12 1 gram per pot applied 7-27-89 and 12-18-89. Osmocote 14-14-14 1.36 grams per pot applied 7-27-89 and 12-18-89.
^YR=rooms, 150 ft-c light.
^XHalf of plant material moved to greenhouse on 9-22-89. Half of plant material remained in rooms.
^wGH = greenhouse, 1500 ft-c light.