Effects of Production Fertilizer Rate and Indoor Light Level on Postharvest Performance of Rieger Begonias

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C.A. Conover, Ph.D. and K. Steinkamp*

University of Florida/IFAS
Institute of Food and Agricultural Sciences
Central Florida Research and Education Center
Apopka Research Report RH-95-3

Interiorscape firms continue to search for blooming plants that have long usable lives in interior installations. The industry standard of two or three week rotation schedules for blooming material is based on the more widely used flowering plants such as chrysanthemums (Harless, 1992). Production and post-production practices that can extend the length of time chrysanthemums and poinsettias remain attractive under interior conditions have been determined (Nell, T. A., 1991; Nell, T. A. et al., 1990).

Bromeliads, orchids and azaleas, are changed less often, but other less commonly used flowering plants can also remain of usable quality for much longer than two to three weeks in adequately lighted interiors. Interiorscapers need to know how long some of these less frequently used blooming plants will remain attractive under interior conditions.

In previous research we showed that, under medium to high interior light levels (12 to 24µmol•s^-1m^-2 or 150 to 300 ft-c), two cultivars of fibrous-rooted begonias (Begonia semperflorens-cultorum 'Prelude Scarlet' and 'Vodka') remained of good to fair quality for up to nine weeks of simulated interiorscape use (Conover, et al., 1993). In the research described here, we produced excellent quality crops of two cultivars of Rieger begonias (Begonia x hiemalis Fotsch.), 'Annebell' and 'Radiant Red', using three different fertilizer levels, then maintained plants in simulated interior environments under four light intensities for nine weeks.

On December 8, 1993, starter plants of Rieger begonia cultivars 'Annebell', a pale to medium yellow color, and 'Radiant Red', a medium red shade, donated from Ball Seed Co., West Chicago, IL 60185, were transplanted from 7-cm (3-inch) containers into 15-cm (6-inch) plastic azalea pots. A peat based commercial growing medium (Fafard #4, Fafard of Florida, Inc., Apopka, FL 32703-8504) amended with 0.59 kg/m³ (1 lb/yd³) of a micronutrient supplement (Micromax, The Scotts Company, 6656 Grantway, Allentown, PA 18106) was used. Plants were grown to salable size in a glass greenhouse where maximum light intensity was 228 µmol•s^-1m^-2 (1200 ft-c) and air temperatures ranged from 18 to 32C (65 to 90°F). Plants were watered as needed to maintain a moderately moist growing medium. Containers were topdressed with 4.0, 5.5 or 7.0 g (1.4, 1.9 or 2.5 oz) 14-14-14 controlled release fertilizer (Osmocote, The Scotts Company) on December 13, 1993.

Rieger begonias are a winter-flowering plant, requiring cooler night temperatures and twelve-hour nights for maximum bud set. Following standard industry procedures, plants were given 1.9 ymols-lm-2 (10 ft-c) supplemental lighting on a LD:SD:LD schedule to promote vegetative growth and induce bud set. On January 14, 1994, the few flower buds showing color were removed to promote vegetative growth and encourage uniformity in the final crop.

Plant height and width (cm), were measured on February 2, 1994, and plant size was determined using the formula; (plant height + plant width) /2 = plant size. Total number of open flowers and buds per plant were counted separately on February 2, 1994. Total bloom after greenhouse production phase was determined using the formula; total open flowers + total buds = total bloom. On February 4, 1994, begonias were graded based on a scale of 1 = dead, 2 = poor quality, unattractive, 3 = fair quality, acceptable for interiorscape use, 4 = good quality, attractive and 5 = excellent quality, very attractive.

On February 7, 1994, plants were placed in interior environment rooms where light intensity, provided by cool white fluorescent bulbs, was maintained at 12, 24, 36 or 48 µmol•s^-1m^-2 (75, 150, 225 or 300 ft-c) for twelve hours daily. Air temperature range was limited to 20 to 26.5°C (68 to 80°F). On March 1, after plants had been in rooms for three weeks, they were graded using the same scale as described earlier. Both number of flowers and number of buds per plant were counted. Plants were also graded and number of flowers and buds counted on March 23, after plants had spent six weeks in rooms and again on April 11, 1994, after plants had received nine weeks of simulated interiorscape use.

Results

Fertilizer rate had no effect on plant size or plant grade, determined in early February when greenhouse production phase was completed (data not shown). Average plant grade after greenhouse production for both cultivars tested was 4.1 and average total bloom after greenhouse production was 12.5 for 'Annebell' and 10.0 for 'Radiant Red'. Production fertilizer rate also did not influence growth, quality or blooming of 'Annebell' or 'Radiant Red' during simulated interior use (data not shown).

A linear relationship between plant deterioration rate and interior light intensity was found. During simulated interiorscape use, plant grade change over time shows plant quality, for both 'Annebell' and 'Radiant Red', declined sooner for begonias under the lower light levels (Table 1). Plants maintained at the two highest light levels were still in good condition after nine weeks of simulated interior use, while plants under 12 µmol•s^-1m^-2 (75 ft-c), the lowest light intensity used, were in fair condition after six weeks in rooms (Table 1). Number of blooms per plant also increased as interior light intensity increased (Table 2).

After nine weeks in rooms, plant grade of 'Annebell' maintained under 48 µmol•s^-1m^-2 (300 ft-c) was still equal to plant grade received after greenhouse production, while plant grade of 'Radiant Red' was actually higher after plants had spent nine weeks under 48 µmol•s^-1m^-2 (300 ft-c) compared to plant grade after production. This could have been due to the fact that Rieger begonias are typically sold when the first few buds are opening so that consumer enjoyment of the blooming period can be maximized. Consequently, plants had more open blooms after nine weeks in rooms compared to when graded after greenhouse production (Table 2).

Conclusions

With as little as 12 µmol•s^-1m^-2 (75 ft-c) interior light intensity, both of the Rieger begonia cultivars tested, 'Annebell' and 'Radiant Red', remained usable for up to six weeks. Plants under 24 to 48 µmol•s^-1m^-2 (150 to 300 ft-c) remained usable for up to nine weeks, at least three times longer than the standard two to three week rotation period commonly used for blooming plant material in interior installations. Lengthening the time between rotations on Rieger begonia plantings translates into savings on plant material, labor and installation time for the interiorscape firm.

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References

1. Conover, C. A., L. N. Satterthwaite and K.G. Steinkamp. 1993. Production fertilizer and postharvest light intensity effects on begonias. Proc. Fla. State Hort. Soc. 106:299-302.
2. Harlass, S. 1992. Painting the interior landscape. Interior Landscape 9(5):38-43.
3. Nell, T. A. 1991. Production and handling practices to increase potted chrysanthemum and poinsettia. Ohio Florist's Assoc. Bull No. 744. pp. 1-3.
4. Nell, T. A., R. T. Leonard and J. E. Barrett. 1990. Production and post-production irradiance affects acclimatization and longevity of potted chrysanthemum and poinsettia. J. Amer. Soc. Hort. Sci. 115(2):262-265.

1. Table 1. Experiment 93-37. Effects of indoor light intensity on plant grade of two cultivars of Rieger begonias.
   

^zPlants were graded based on a scale of 1 = dead, 2 = poor quality, unattractive, 3 = fair quality, acceptable for interiorscape use, 4 = good quality, attractive and 5 = excellent quality, very attractive, after greenhouse production, after plants had spent three, six and nine weeks in rooms (on February 4, February 28, March 22 and April 11, 1994). ^yPlant grade change after 3, 6 and 9 weeks indoors was determined by the formula plant grade after production - plant grade after 3, 6 or 9 weeks indoors. ^xns, **; Nonsignificant or significant at P = 0.01, respectively.

Table 2. Experiment 93-37. Effects of indoor light intensity on flowering of two cultivars of Rieger begonias.

^zNumber of open flowers, number of flower buds per plant were counted after greenhouse production and after plants had spent 3, 6 and 9 weeks indoors (on February 2, February 28, March 23 and April 15, 1994).
^yTotal number of blooms was determined after plants had spent 3, 6 and 9 weeks in rooms by the following formula; number of flowers per plant + number of buds per plant = total bloom.
^xns, *, **; Nonsignificant, significant at P = 0.05 or significant at P = 0.01, respectively.

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