C.A. Conover, Russell Caldwell and K.
Steinkamp*
Growth, quality and water requirements of Araucaria
heterophylla (Norfolk Island pine), Chamaedorea
elegans (parlor palm), Epipremnum aureum (golden
pothos) and Radermachera sinica (China doll) were
determined for plants in self-watering containers maintained
indoors under 50, 100, 150 or 200 ft-c for 180 days. Amount
of water used was dependent on light intensity and was
specific to plant type. All plants used more water as light
level increased.
Good quality acclimatized foliage plants, if properly
cared for, can be maintained indoors indefinitely. Water
stress, often caused by over- or under-watering, damages root
systems which can lessen attractiveness and plant longevity.
Self-watering containers, designed to regulate growing medium
moisture levels, are available to interiorscapers and retail
consumers.
Interiorscape firms and consumers need more information on
watering requirements of plants in self-watering containers
when maintained under different indoor conditions. The
following experiment was conducted to determine water
requirements of four foliage plants in self-watering
containers placed under four indoor light intensities.
Materials and Methods
On November 9, 1992, good quality Araucaria
heterophylla (Norfolk Island pine), Chamaedorea
elegans (parlor palm), Epipremnum aureum (golden
pothos) and Radermachera sinica (China doll) were
transplanted from standard plastic 15 cm production pots into
16.5 cm diameter, 18 cm tall self-watering containers
(Decor® Watermatic™, Decor America Incorporated,
Compton, CA 90220). Vergro Container Mix A (Verlite Co.,
Tampa, FL 33610) was used as the growing medium. Average
initial height was 39 cm for Norfolk Island pine, 49 cm for
parlor palm, 22 cm for China doll and 7 cm for golden pothos
(vine length).
On November 13, 1992, plants were placed in interior
environment rooms illuminated with 40 watt cool white
fluorescent bulbs. Light intensity indoors was 50, 100, 150
or 200 ft-c, for twelve hours daily. Air temperature ranged
from 70 to 80°F and relative humidity was 50 ± 5%. There
were five replications per light level for each plant type
tested.
Plants were fertilized the same day with 1.375 g/L (50 mg
N/L) 20-20-20 (N-P2O5-K2O)
from a stock solution. Watering reservoirs were filled with
100 ml stock solution plus 450 ml water so that plants were
fertilized at 0.7 g 20-20-20/6 inch pot/4 months. Water
levels in reservoirs were monitored daily and refilled with
550 ml tap water when empty.
Plant height (vine length of two longest vines per pot for
golden pothos) was measured initially on November 13, 1992
and at monthly intervals thereafter. At three and six months,
plants were graded on the following scale: 1 = dead; 2 = poor
quality, unattractive; 3 = fair quality; 4 = good quality,
attractive and 5 = excellent quality, very attractive. Total
volume of water placed in water-holding reservoirs that was
utilized was recorded. Number of days between waterings,
number of waterings while indoors, and fresh weight of
foliage were determined when the experiment was terminated.
Results
The self-watering containers worked well, keeping growing
medium moist. Norfolk Island pine quality improved as light
intensity increased, from fair, for plants under 50 or 100
ft-c, to attractive for plants under 150 or 200 ft-c (Fig.
1). Both height and fresh top weight increased slightly with
increased light intensity (Figs. 2 and 3).
Parlor palm were attractive and of comparable height under
any of the four indoor light levels tested (Figs. I and 2),
with an average height of 55 cm. However, the fresh top
weight increase seen with increasing light intensity
indicated plants produced more foliage under higher light
intensities (Fig. 3). Although all parlor palms were still
attractive after 180 days indoors, fertilization rate
appeared inadequate for plants under 150 or 200 ft-c, which
were a lighter green color compared to plants maintained
under 50 or 100 ft-c.
Golden pothos under 50 ft-c were of fair quality, while
those under 100, 150 or 200 ft-c were judged attractive after
180 days indoors (Fig. 1). Both vine length and fresh top
weight increased when light intensity was increased from 50
to 100 ft-c (Figs. 2 and 3).
For China doll, plant quality, height and fresh top weight
increased as light intensity increased (Figs. l, 2 and 3).
Although only plants under high light were judged attractive
when research was terminated, this light intensity (200 ft-c)
was lower than the recommended minimum for acclimatized China
doll plants (225 ft-c).
Water requirements of all plants increased with increases
in light intensity and amount of water needed over the 180
days was dependent on plant type (Fig. 4). For plants
maintained under 200 ft-c, China doll, with the smallest top
weight (174.2 g), required 17,500 ml water, while golden
pothos, with the largest fresh top weight (460.2 g) required
13,060 ml. Parlor palm needed more water when maintained
under 50 ft-c than other plant types, probably because palms
were better able to grow and maintain attractiveness under
this low light condition (indicated by plant grades).
Number of days between waterings depended on light
intensity and plant type (Fig. 5). Average number of days
between waterings of Norfolk Island pine, golden pothos and
China doll under 50 ft-c was twenty-two days, while parlor
palm in the low light averaged sixteen days between
waterings. Although number of days between waterings
decreased as light intensity increased for all plants tested,
rate of decrease was also dependent on plant type. Under 200
ft-c, China doll needed watering an average of every six
days, parlor palm every seven days and Norfolk Island pine
and golden pothos both needed watering every eight days.
Conclusions
Overall, the self-watering containers worked well.
Although China doll was in poor condition after six months
under 50 ft-c, quality of Norfolk Island pine and golden
pothos under 50 ft-c was also lower than quality of plants
under higher light.
Water use was related to plant quality and growth. Plants
that grew well in the lower light levels needed more water
than plants less suited to those light levels. Water
requirements were affected by interior light intensity, with
water needs increasing as light intensity increased. Water
requirements and rate of increased need for water when light
level increased was also dependent on plant type.
*Center Director and Professor of Environmental
Horticulture (retired 7/96), Biological Scientist, and
Technical Assistant, respectively, Central Florida Research
and Education Center-Apopka, 2807 Binion Road, Apopka, FL
32703-8504
References
- Conover, C.A. and R.T. Poole. 1992. Water utilization
of six foliage plants under two interior light
intensities. J. Environ. Hort. 10(2):11-113.
- Conover, C.A. and R.T. Poole. 1981. Influence of
light and fertilizer level and fertilizer sources on
foliage plants maintained under interior environments
for one year. J. Amer. Soc. Hort. Sci. 106:571-574.
- Conover, C.A., R.T. Poole and R.W. Henley. 1991.
Light and fertilizer recommendations for the interior
maintenance of acclimatized foliage plants. Foliage
Digest 16(11):1-4.
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