Reaction of Seven Foliage Plants to Sodium Hypochlorite Fumes or Drenches

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University of Florida,
Central Florida Research and Education Center-Apopka
CFREC-Apopka Research Report RH-92-25

R.T. Poole and R.W. Henley*

Sodium hypochlorite (NaOCl) is an effective algicide often used to clean greenhouse structures. Solution fumes do not seem to harm foliage plants, but plants are usually exposed to the algicide briefly during production, depending on rate of algae regrowth. NaOCl, in low concentrations, is also commonly used to control algae growth in ebb and flow systems with no detrimental effects. However, when NaOCl is used in swimming pool water quality maintenance, plantscapes around spas and pools are constantly exposed to NaOCl, in the air and from splashing, at higher rates than in closed watering systems. The two experiments described below were conducted to determine the reaction of seven foliage plants receiving a one-time sodium hypochlorite drench or constant fumes for one week.

Materials and Methods

Species tested were Dizygotheca elegantissima (false aralia), Dracaena deremensis 'Janet Craig' ('Janet Craig' dracaena), Ficus benjamina (weeping fig), Ficus elastica 'Robusta' ('Robusta' rubber tree), Homalomena 'Emerald Gem' ('Emerald Gem' homalomena), Philodendron scandens oxycardium (heart-leaf philodendron) and Polyscias fruticosa (Ming aralia). All were good quality ready-for-sale plants obtained from local nurseries. Plants had been grown in 4, 6, 8 or 10-inch pots, depending on species, using various commercial growing media.

Experiment 1 measured plant sensitivity to NaOCl solution fumes. Upon arrival at CFREC-Apopka, plants were placed in 10 x 10 x 8 ft rooms for a 1 week period. Light intensity in rooms, from cool white fluorescent lights, was 200 ft-c and air temperature was maintained at 75F. Plants in rooms spent the week enclosed in sealed airtight 1 x 1 x 2 ft glass containers with a 100 ml beaker holding 50 ml sodium hypochlorite solution (5.25% active ingredient by weight) or unenclosed on floor of rooms.

Experiment 2 tested reactions to sodium hypochlorite drenches. Soon after arrival at CFREC-Apopka, plants were placed in 10 x 10 x 8 ft rooms, adjacent to rooms used in experiment 1, where they were maintained for a 1 week period. As in experiment 1, light intensity in rooms was 200 ft-c and air temperature was 75F.

Growing medium of plants was drenched with 20% of a 5 % sodium hypochlorite solution or tap water. Amount of solution each plant received was determined by pot size. Plants in 4-inch pots received 50 ml, 6-inch pots got 100 ml, 8-inch pots got 150 ml and plants in 10-inch pots were drenched with 200 ml of 20% of a 5% sodium hypochlorite solution or tap water.

After one week in rooms, plants were moved to a greenhouse where maximum light intensity was 1500 ft-c and air temperatures ranged from 65 to 90F. Plants were maintained in greenhouses for up to two months in order to evaluate effects of treatments. When visible signs of damage were fully developed on individual species that were sensitive, those plants were graded. Plant grades were determined based on a scale of 1 = dead, 2 = poor, unsalable, 3 = fair, salable, 4 = good quality and 5 = excellent quality. Inspection and evaluation dates are given in Table 1.

In experiment 1, NaOCl fumes did not appear to harm any of the 7 species tested. Plants enclosed with fumes were not visibly damaged and quality was unaffected by treatment.

Results of experiment 2 showed recent and new growth on 'Emerald Gem' homalomena and Ming aralia receiving drenches was necrotic. Necrosis was severe enough to degrade quality of both species from excellent to poor. The 5 other species tested were unaffected by drench treatments.

Based on these experiments, 'Emerald Gem' homalomena and Ming aralia would be inappropriate for inclusion in plantscapes situated close enough to be splashed with chlorinated pool or spa water.

*Professor of Plant Physiology, and Professor of Environmental Horticulture and Extension Specialist, respectively, Central Florida Research and Education Center-Apopka, 2807 Binion Road, Apopka, FL 32703-8504.

Table 1. Dates when fume and drench treatments were initiated and dates when foliage was inspected for damage for the eight species used two experiments initiated on 30 April and concluded on 30 June 1992.

Plant Date treatedz Date
Dizygotheca elegantissima 30 Apr to 7 May 10 Jun
Dracaena deremensis
'Janet Craig'
27 May to 4 Jun 10 Jun
Ficus benjamina 1 Jun to 8 Jun 10 Jun
Ficus elastica
23 Apr to 30 Apr 10 Jun
'Emerald Gem'
30 Apr to 7 May 10 Jun
Philodendron scandens
2 Jun to 9 Jun 30 Jun
Polyscias fruticosa 16 Apr to 23 Apr 28 Apr

zPlants placed in rooms for one week were either drenched with 20% NaOCl solution when placed in rooms, enclosed in airtight glass containers with 50 ml NaOCL for the entire 7 day period or were part of control groups which received no NaOCI.