Effects of Light Intensity and Fertilizer Formulation
on Six Foliage Plants Growing Indoors

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R. T. Poole and C. A. Conover*

University of Florida, IFAS
Central Florida Research and Education Center - Apopka
CFREC-Research Report, RH-90-16

Ideally, foliage plants in the interior environment should maintain original quality and grow slowly. Interiorscapers need to know if fertilizer formulation affects indoor plant maintenance and also if fertilizer formulations should change as light intensities increase or decrease. The following experiment, initiated July 20, 1989, examined the effects of fertilizer formulation on six species of foliage plants maintained under three light intensities in rooms simulating an interior environment.

All plant material utilized were finished, ready for sale plants, growing in six inch pots, obtained from commercial growers and included; Aglaonema 'Silver Queen' (Silver Queen aglaonema), Alpinia variegata (Shell ginger), Chamaedorea elegans (Parlor palm), Codiaeum variegatum 'Petra' (Petra croton), Dracaena fragrans 'Massangeana' (Striped corn plant), and Nephrolepis exaltata 'Dallas' (Dallas fern). Plants were placed in rooms receiving 75, 150 or 225 ft-c light, 12 hours daily, from cool white fluorescent bulbs. Temperature ranged from 70 to 80░F and plants were irrigated 1 to 2 times a week as needed. Fertilizer treatments included applying 2 grams per pot 19-6-12 Osmocote or 2.7 grams per pot 14-14-14 Osmocote. Osmocote is manufactured by Sierra Chemical Co., Milpitas, CA. Both fertilizers have three month-release durations and were applied initially July 20 and again on October 20. Therefore, all plants received the same amount of nitrogen, the most influential element in foliage plant growth. Soluble salts were measured July 26, October 30, and January 18 using the pour-through method. Height was measured initially July 26 and again October 12 and January 18. Plants were graded on a scale of 1=poor, unsalable; 3=average, salable and 5=excellent quality. On September 26, (Ca(OH)2 (calcium hydroxide) 1 tsp/L solution was applied 100 ml/pot to the Chamaedorea elegans to correct acidic pH.

Plants receiving higher light intensities were taller at termination of the experiment than plants maintained under the lower light intensities, except for Aglaonema 'Silver Queen' (Table 1). Plant grade of Alpinia variegata and Chamaedorea elegans receiving 75 ft-c was higher January 18, 1990 than October 30, 1989, but grades of other cultivars maintained under 75 ft-c were lower at 6 months than at 3 months. Plant grade after 6 months was highest for plants maintained under 225 ft-c. These plants showed the most improvement in quality or the least amount of deterioration after 6 months (Table 2).

Soluble salts levels of the leachate usually decreased with time and were lower at 225 ft-c. Plants grew more, thus utilized more fertilizer at 225 ft-c than at the lower light levels tested. These two factors account for electrical conductivity of pots decreasing as light levels increased (Table 3).

Fertilizer formulation had no effect on soluble salts levels, plant growth or grade. Fertilizer formulation did have a significant effect on amount of phosphorus and potassium found in leachate of Codiaeum variegatum 'Petra'. Leachate from pots containing plants receiving 14-14-14 contained over twice as much phosphorus as leachate collected from pots with plants receiving 19-6-12 (Table 4). Since plants used less fertilizer at lower light levels, fertilizer application rates can be reduced when plants are maintained in a low light intensity environment to save money and reduce pollution of the environment.
Since formulation had no effect on plant growth, a ratio of 3:1:2 (N-P205-K2O) should be used instead of fertilizers with P and K equal to N (1-1-1) or higher than N (1-3-2) to minimize pollution from phosphates and potash.
Of the plants tested, Aglaonema 'Silver Queen' and Chamaedorea elegans appear to maintain best quality when subjected to low light intensities for prolonged periods.


  1. *professor of Plant Physiology, and Professor and Center Director, respectively. Central Florida Research and Education Center - Apopka, 2807 Binion Rd., Apopka, FL 32703-8504

Additional Reading

  1. 1. Poole, R T. and A. R Chase. 1987. Response of foliage plants to fertilizer application rates and associated leachate conductivity. HortScience 22(2):317-318.

    2. Conover, C. A. and R T. Poole. 1984. Acclimatization of indoor foliage plants.Horticultural Review 6:119-154.

    3. Conover, C. A. and R T. Poole. 1981. Influence of light and fertilizer level and fertilizer sources on foliage plants maintained under environments for one year. J. Amer. Soc. Hort. Sci. 106(5):571-574.

    4. Turner, M. A., D. L. Morgan and D. W. Reed. 1987. The effect of light quality and fertility on long term interior maintenance of selected foliage plants. J. Environ. Hort. 5(2):76-79.

    5. Wright, R D. 1986. The pour-through nutrient extraction procedure. HortScience 21:227-229.


Table 1. Height (cm) of foliage plants placed in interior rooms Jul 20, 1989. Data taken Oct 12, 1989 (I) and Jan 18, 1990 (II).
  Aglaonema 'Silver Queen' Alpinia variegata Chamaedorea elegans Codiaeum 'Petra' Dracaena 'Massangeana' Nephrolepis 'Dallas'
ft-c, 12
hr/day
I II I II I II I II I II I II
75 43 44 66 66 62 63 19 20 56 62 39 39
150 43 44 66 72 67 68 21 26 59 66 42 40
225 44 44 74 76 66 66 21 26 68 75 41 43


Table 1. cont.

Growth (cm) from Jul 20 to Jan 18.
ft-c, 12 hr/day Aglaonema 'Silver Queen' Alpinia variegata Chamaedorea elegans Codiaeum 'Petra' Dracaena 'Massangeana' Nephrolepis 'Dallas'
75 1.2 1.7 5.9 1.7 13.9 2.9
150 2.1 8.3 7.5 6.9 17.7 3.0
225 1.1 13.0 10.6 7.6 23.7 9.2

Table 2. Plant grade of foliage plants placed in interior rooms Jul 20, 1989.
Data taken Oct 30, 1989 (I) and Jan 18 1990 (II)
  Aglaonema 'Silver Queen' Alpinia variegata Chamaedorea elegans Codiaeum 'Petra' Dracaena 'Massangeana' Nephrolepis 'Dallas'
ft-c,12 hr/day I II I II I II I II I II I II
75 4.1 3.4 2.4 2.6 3.5 3.9 4.1 3.2 3.8 3.2 3.4 2.9
150 4.0 3.8 3.8 3.3 3.7 4.2 4.2 3.7 4.0 3.6 3.9 3.6
225 4.5 4.6 3.5 3.9 3.6 4.5 4.5 4.4 4.5 4.2 4.0 4.2

Table 3. Electrical conductivity (Áhos/cm) of pot containing foliage plants placed in interior rooms Jul 20, 1989.
Data taken
Jul 26, 1989 (I), Oct 30 1989 (II), and Jan 18, 1990 (III).
  Aglaonema 'Silver Queen' Alpinia variegata Chamaedorea elegans
ft-c, 12 hr/day I II III I II III I II III
75 1274 628 787 490 777 811 1519 1013 1578
150 1227 542 653 388 489 547 1368 1562 1812
225 1314 670 555 360 476 553 1293 696 567
 
  Codiaeum 'Petra' Dracaena 'massangeana' Nephroleplis 'Dallas'
ft-c, 12 hr/day I II III I II III I II III
75 3272 2142 2008 830 1009 744 1317 448 550
150 2828 2602 2872 867 786 611 963 302 185
225 2644 1250 2432 853 904 551 1119 280 169

Table 4. Phosphorus, ammonium (NH4+), and nitrates (NO3-) measured as mg/L in leachate of Codiaeum variegatum 'Petra' placed in interior rooms July 20, 1989. Leachate collected January 17, 1990.
Fertilizer Source P NH4+ NO3-
19-6-12Z 14.9 1.0 163.9
14-14-14Y 29.9 0.5 187.3
Significant effectsX ** ns ns
       
Light intensity
75 ftc 24.3 0.7 160.0
150 ftc 24.7 0.7 179.1
225 ftc 17.7 0.9 187.7
       
Significant effectsX
linear ns ns ns
quadratic ns ns ns
  1. Z19-6-12 three month release rate Osmocote was applied 2 grams/pot July 20 and October 20.
    Y14-14-14 three month release rate Osmocote was applied 2.7 grams/pot July 20 and October 20.
    Xns and **; Nonsignificant and significant at the 5% level.