Effects of Nitrogen and Potassium Fertilization Ratios on Growth and Flowering of Three Anthurium Hybrids

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C.A. Conover, Ph.D. and R.J. Henny, Ph.D.*

University of Florida/IFAS
Central Florida Research and Education Center
CFREC-Apopka Research Report RH-95-2

Anthuriums have been grown primarily as a cut flower crop, valued for their colorful long lasting spathe and spadix. The large leaves and long flower stalks of most anthurium species make them unsuitable for use as potted plants. Although a few pot-type anthuriums have been grown commercially, only recently have new anthurium hybrids, with smaller leaves and "flowers" at foliage level, been bred especially for the containerized market. More hybrids are still in the developmental stage.

Limited information about fertilization has been published for anthurium as a pot crop, but the currently recommended rate is 1200 to 1500 lbs N/A/yr, or about 3.7 g N/6-inch pot/yr, when plants are grown under 1500 to 2000 ft-c (Conover and Poole, 1988; Conover and Poole, 1990; Henny, et al, 1991). A 1-1-1, N-P-K ratio fertilizer produced satisfactory results.

In the Netherlands, Anthurium andreanum (a cut flower anthurium) grown in sphagnum peat produced best flower yield, weight, stem and spathe length and width when fertilized with 125 mg N and 225 mg K/3.3 gal-pot/week, a N:K2O ratio of 1:2.5 (Bik, 1976). The following experiment was conducted to determine growth and flowering of three new cultivars of anthuriums being developed for the pot market when plants were fertilized with various nitrogen (N) and potassium (K) rates and N:K ratios.

On April 20, 1993, tissue cultured plantlets of three new anthurium cultivars labeled BA43-Cherry, BA43-Lavender and BA14-Red were transplanted from 72-cell plug trays into 6-inch (15-cm) pots, one per pot, using a commercially manufactured growing medium suited for anthuriums (Fafard #3, Fafard of Florida Inc., 3723 Hogshead Road, Apopka, FL 32703). Growing medium was amended with 1 lb/yd3 (0.6 kg/m3) MicroMax (The Scotts Company, 6656 Grantway, Allentown, PA 18106). Plants were grown on wire benches in a greenhouse where maximum light intensity was about 1200 ft-c and air temperatures ranged from 65 to 90F.

A 4 nitrogen rate x 4 potassium rate factorial experiment, with 4 replications per treatment was established. Plants were fertilized once a week with 150 ml N-P-K liquid fertilizer made from stock solutions of NH4NO3, H3PO4 and KC1. Fertilization rates were phosphorous (P) at 400 lb/A/yr, N at 900, 1500, 2100 or 2700 lbs/A/yr and K at 900, 1500, 2100 or 2700 lbs/A/yr (1.85, 3.07, 4.30 or 5.52 g/6-inch pot/yr).

Number of new flowers per plant was recorded weekly and then totaled when the experiment was terminated on January 20, 1994. Other terminal data collected on that date included plant grade, leaf area, plant size and number of new shoots. Plants were graded based on a scale of 1 = dead, 2 = poor quality, unsalable, 3 = fair quality, salable, 4 = good quality and 5 = excellent quality. Leaf area (cm3) of the three largest leaves per plant was measured and plant size (cm) was determined using the formula: (height + width)-2.

Results

Anthurium BA43-Cherry. Interaction of N and K fertilization significantly affected plant grade of BA43-Cherry after nine months production time. Plant grade decreased as total amount of fertilizer applied increased, probably due to excess total salts (Table 1). As N application rate increased from the lowest to the highest rate tested, leaf area decreased 32%, plant size 18% and number of flowers 85% (Table 2). Number of new shoots produced over the course of the experiment was greatest when plants received 1500 or 2100 lb/A/yr, the two middle N levels tested.

Anthurium BA43-Lavender. All plant measurements except number of new shoots per pot decreased as fertilization rate increased from 900 to 2700 lb N/A/yr (Table 3). Plant grade decreased by 40%, leaf area by 23%, plant size by 18% and number of flowers produced decreased by 59%. Potassium rate had no significant effect on BA43-Lavender.

Anthurium BA14-Red. Except for number of new shoots produced per plant (not influenced by fertilization rates tested), data obtained from BA14-Red also showed decreases as N fertilizer rate increased (Table 4). When comparing plants getting the lowest N rate to plants getting the highest N fertilization rate used, a plant grade decrease of 20%, a leaf area decrease of 15%, a 10% decrease in plant size and a 74% decrease in the number of flowers produced per plant was observed. Increasing potassium level also affected BA14-Red plant grade and leaf area with decreases of 17% and 11% respectively as K fertilizer rate increased (Table 5).

Conclusions

Data presented indicate that the lower N and K fertilizer rates tested produced the highest quality plants. Not only was plant appearance improved at the lower fertilizer levels, but also flowering was much better, with increases of 59 to 85 %, depending on cultivar. Lack of early flowering, which lengthens crop turnover time, has been somewhat of a problem with many of the anthurium pot plant cultivars under development. Results from this experiment suggest the flowering problem may possibly be due in part to use of excessive levels of fertilizer, particularly nitrogen. Additional research is needed on these cultivars but based on data presented here, use of 900-1200 lb N/A/yr from a 1-1-1ratio fertilizer such as a liquid 20-20-20 or slow release 14-14-14 Osmocote (The Scotts Company, 665- Grantway, Allentown, PA 18106) would be suggested.

Table 1. Interaction effects of fertilizer N:K ratio on plant grade^z of anthurium hybrid BA43-Cherry grown in 6-inch pots from April 20, 1993 until January 20, 1994.

Interaction significant at P = 0.0142.
^zPlants were graded based on a scale of 1 = dead, 2 = poor quality, unsalable, 3 = fair quality, salable, 4 = good quality and 5 = excellent quality on January 20, 1994.

Table 2. Effects of nitrogen rate on anthurium BA43-Cherry grown in 6-inch pots from April 20, 1993 until January 20, 1994.

^zPlants were graded based on a scale of 1 = dead, 2 = poor quality, unsalable, 3 = fair quality, salable, 4 = good quality and 5 = excellent quality on January 20, 1994.
^yAverage leaf area (cm3) of the three largest leaves per plant was measured on January 20, 1994.
^xPlant size (cm) on January 20, 1994 was measured as (height + width) / 2.
^wTotal number of flowers produced per plant during the nine month production period.
^vNumber of new shoots per plant was counted on January 20, 1994.
^uns, *, **; Nonsignificant, significant at P = 0.05 or significant at P = 0.01, respectively.

Table 3. Effects of nitrogen rate on anthurium BA43-Lavender grown in 6-inch pots from April 20, 1993 until January 20, 1994.

^zPlants were graded based on a scale of 1 = dead, 2 = poor quality, unsalable, 3 = fair quality, salable, 4 = good quality and 5 = excellent quality on January 20, 1994.
^yAverage leaf area (cm3) of the three largest leaves per plant was measured on January 20, 1994.
^xPlant size (cm) on January 20, 1994 was measured as (height + width) / 2.
^wTotal number of flowers produced per plant during the nine month production period.
^vNumber of new shoots per plant was counted on January 20, 1994.
^uns, *, **; Nonsignificant, significant at P = 0.05 or significant at P = 0.01, respectively.

Table 4. Effects of nitrogen rate on anthurium BA14-Red grown in 6-inch pots from April 20, 1993 until January 20, 1994.

^zPlants were graded based on a scale of 1 = dead, 2 = poor quality, unsalable, 3 = fair quality, salable, 4 = good quality and 5 = excellent quality on January 20, 1994.
^yAverage leaf area (cm3) of the three largest leaves per plant was measured on January 20, 1994.
^xPlant size (cm) on January 20, 1994 was measured as (height + width) / 2.
^wTotal number of flowers produced per plant during the nine month production period.
^vNumber of new shoots per plant was counted on January 20, 1994.
^uns, *, **; Nonsignificant, significant at P = 0.05 or significant at P = 0.01, respectively.

Table 5. Effects of potassium rate on anthurium BA14-Red grown in 6-inch pots from April 20, 1993 until January 20, 1994.

^zPlants were graded based on a scale of 1 = dead, 2 = poor quality, unsalable, 3 - fair quality, salable, 4 = good quality and 5 = excellent quality on January 20, 1994.
^yAverage leaf area (cm3) of the three largest leaves per plant was measured on January 20, 1994.
^xns, *, **; Nonsignificant, significant at P = 0.05 or significant at P = 0.01, respectively.

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

References

1. Bik, R. Arnold. 1976. Quality in anthurium and Aechmea fasciata grown in peat substrates as affected by nitrogen and potassium nutrition. Acta Horticulturae 64:83-91.
2. Conover, C.A. and R.T. Poole. 1990. Light and fertilizer recommendations for production of acclimatized potted foliage plants. Nursery Digest 24(10):34-36, 58-59.
3. Conover, C.A. and R.T. Poole. 1988. Flowering crops for foliage growers. Univ. of Fla., CFREC-Apopka Res Rpt RH-88-9.
4. Henny, R.J., A.R. Chase and L.S. Osborne. 1991. Univ. of Fla., CFREC-Apopka Fol. Plant. Res. Note RH-91-3.