Effects of Moisture Stress During Simulated Shipping on Quality of Dracaena 'Massangeana', Dwarf Schefflera and Weeping Fig

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C.A. Conover, Ph.D.*

University of Florida/IFAS
Central Florida Research and Education Center
CFREC-Apopka Research Report RH-94-3

Summary Growing medium moisture levels during simulated shipping/storage were important for 2 of 3 foliage plants tested. Schefflera arboricola (dwarf schefflera) with growing medium moisture levels ranging from very wet to dry maintained original quality when examined immediately after simulated shipment and again after time spent under indoor conditions. For Ficus benjamina (weeping fig), only plants with growing medium very wet at shipping time maintained original quality after simulated shipping and 10 days or 6 weeks under 125 ft-c. In 1 out of 2 experiments conducted, Dracaena fragrans 'Massangeana' (Dracaena 'Massangeana') plant quality was shown to increase as growing medium moisture level during simulated shipping decreased.

General shipping recommendations for foliage plants include maintaining growing medium moisture levels around 50% so the medium feels moderately moist. However, when following recommended acclimatization procedures for production and shipping, weeping fig and Dracaena 'Massangeana' sometimes incur foliage damage during shipping.

In previous research, weeping fig dropped leaves when subjected to water stress under production or indoor conditions. In numerous simulated shipping tests with Dracaena 'Massangeana', areas of collapsed foliage tissue were observed on a few plants that were watered on the day simulated shipping treatments began. However, numbers of affected Dracaena 'Massangeana' were never large enough to be statistically significant. The following experiments were conducted to further study effects of growing medium moisture levels during simulated shipping on quality of three foliage plant genera.

Materials and Methods

Dracaena 'Massangeana', dwarf schefflera and weeping fig were used for both tests. Experiment 1 was initiated on February 18, 1991, when excellent quality, finished plant material grown in 15-cm (6-inch) pots (Dracaena 'Massangeana' and dwarf schefflera), or 25-cm (10-inch pots (weeping fig), was obtained from local growers. Plants had been grown in commercial potting medium. Plants were placed in a shadehouse under 63% shade where they were maintained for 4 weeks. Shadehouse air temperatures ranged from 60 to 90°F and plants were watered manually 3 to 4 times per week as needed. Plants were top-dressed with 5 g/15cm pot or 10 g/25-cm pot 19-6-12 Osmocote, on February 20, 1991.

Plants were last watered the day simulated shipping began or, 1, 4, 7 or 10 days before simulated shipping. When watered for the final time before simulated shipping treatments began, growing medium was saturated with water. Immediately before and after simulated shipping, weeping fig plants were weighed, so that the weight of water lost from growing medium and plant tissue could be determined.

During simulated shipping, starting on July 19, plants were stored in dark closed coolers maintained at 60°F. Two weeks later, on August 2, plants were removed from coolers, weighed, graded based on a scale of 1 = dead, 2 = poor quality, unsalable, 3 = fair quality, salable, 4 = good quality and 5 = excellent quality, and placed in interior environment rooms simulating typical indoor conditions. Cool white fluorescent bulbs provided 125 ft-c light intensity for 12 hours daily and air temperatures ranged from 70 to 80°F. Plants were watered as needed to keep growing medium moderately moist. After 10 days in rooms, plants were graded again. Leaf loss was included in overall weeping fig plant grades. Plant grades were lowered as amount of foliage remaining on plants decreased.

Experiment 2 began on May 25, 1992, when excellent quality plants in 6-inch pots were obtained from local growers. Plants were top-dressed with 5 g/6-inch pot 19-6-12 Osmocote, then maintained in a shadehouse under the same environmental conditions described in experiment 1. Plants received the same treatments as described in experiment 1. On July 26, after 4 weeks under shadehouse conditions, plants were placed in dark closed coolers. On August 10, 1992, plants were removed from coolers, graded and placed in rooms, again under the same conditions described in experiment 1. On September 18, 1992, after 6 weeks in rooms, plants received a final plant grade.

Results

In both experiments, dwarf schefflera were not affected by growing medium moisture levels during simulated shipping. All dwarf schefflera maintained good quality after simulated shipping and 10 days or 6 weeks under indoor conditions (data not shown).

Quality of weeping fig immediately after storage was better in both experiments when plants were watered on the day of simulated shipping, or 1 day prior, compared to plants watered farther from the beginning of simulated shipping. However, when plants were placed indoors under 125 ft-c for 10 days after simulated shipping, best quality weeping fig were those which had been watered on the day of simulated shipping (Table 1).

For weeping fig watered the day simulated shipping began, or 1 or 4 days before beginning shipping, weight lost from the growing medium and plant tissues during simulated shipping decreased as time of last watering prior to simulated shipping increased (Table 2). However, weight loss from soil and tissue was similar for plants watered 4 or more days before simulated shipping.

For Dracaena 'Massangeana' in experiment 1, plant quality after 10 days in rooms under 125 ft-c was not affected by watering schedule before simulated shipping and plants did not appear damaged. In experiment 2, however, when plants were graded after 6 weeks indoors, plant quality increased as number of days between the last watering and initiation of simulated shipping increased (Table 3).

Conclusions

Dwarf schefflera tolerated a wide range of growing medium moisture levels during simulated shipping/storage without loss of quality indicating plants would not be damaged if the general recommendations for shipping foliage plants (moderately moist growing medium during shipping) were followed.

Plant grade and weight results for weeping fig show that, under the conditions of these tests, weeping fig quality was maintained only when plants were watered on the day simulated shipping began. Both quality and weight loss during simulated shipping increased as watering time before simulated shipping decreased, indicating soil moisture levels in containers of weeping fig should be high during shipment.

In previous research, weeping fig was shown to have very low tolerance to moisture stress (Peterson et al, 1981). As a survival mechanism, moisture stressed weeping figs formed an abscission layer of cells at the point of petiole attachment on some leaves, shedding foliage to decrease plant water requirements. The fact that plants could undergo moisture stress during shipping, which would influence plant quality after interior installation, is an important consideration for growers, shippers and interiorscapers. Therefore, weeping fig should be watered on the day of shipping and immediately after placement into the interiorscape.

Dracaena 'Massangeana' in experiment 1 seemed unaffected by simulated shipping treatments but in experiment 2, when plants were maintained under simulated indoor conditions for 6 weeks, foliage damage decreased as length of time between watering and initiation of simulated shipping increased. In previous experiments, we often observed similar damage (areas of collapsed tissue in foliage) on 1 or sometimes 2 plants in treatments watered the day of simulated shipping. However, in the earlier tests, damage was not wide-spread or severe enough to significantly affect plant grades.

Dracaena 'Massangeana' root systems may be sensitive to low oxygen levels in growing medium. Roots get oxygen from non-capillary pore space in potting soil. Growing medium in pots of Dracaena 'Massangeana' tends to be compacted during potting so that cane will remain upright. While this does not seem to affect plant quality under normal production conditions, where evapotranspiration rates are high, some of the non-capillary pore space (air space) in potting soil is destroyed by compaction. As the growing medium becomes saturated with water, even less pore space is available for oxygen. When plants are in dark closed storage areas (simulated shipping conditions), water loss from evapotranspiration is usually much lower compared to water loss under normal production regimes; thus, insufficient root zone oxygen levels during shipping may be responsible for the decline when this plant is shipped. Until further research is done, we suggest that the growing medium of Dracaena 'Massangeana' should not be saturated with water during shipping, and should be shipped with growing medium somewhat dry.

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

References

1. Conover, C.A. and R.T. Poole. 1986. Factors influencing shipping of acclimatized foliage plants. Univ. of Fla., Agri. Res. Cntr., CFREC-Apopka Res. Rpt. RH-86-11.
2. Peterson, J.C., J.N. Sacalis and Dominic J. Durkin. 1981. Ficus benjamina: Avoid water stress to prevent leaf shedding. Florist's Rev. 167(4335):10-11, 37-38.
3. Poole, R.T. and C.A. Conover. 1983. Influence of simulated shipping environments on foliage plant quality. HortScience 18(2): 191- 193.
4. Poole, R.T. and C.A. Conover. 1987. Effect of environmental factors on Dracaena 'Massangeana' during shipping. Proc. Fla. State Hort. Soc. 100:340-341.

Table 1. Effects of medium moisture level during simulated shipping on plant grade of Ficus benjamina. Exp. 1.

^zPlants were last watered on the day simulated shipping was initiated, or 1, 4, 7 or 10 days before simulated shipping began.
^yPlants were graded based on a scale of 1 = dead, 2 = poor quality, unsalable, 3 = fair quality, salable, 4 = good quality and 5 = excellent quality.
^xSignificance determined using Duncan's Multiple Range Test, 5% level. Means in the same column with the same letter are not significantly different.

Table 2. Weight loss from Ficus benjamina containers during storage affected by medium moisture level before simulated shipping. Exp. 1.

^zPlants were last watered on the day simulated shipping was initiated, or 1, 4, 7 or 10 days before simulated shipping began.
^yPlants, container and growing medium were weighed together as a unit immediately before simulated shipping was initiated on July 19, and again immediately after plants were removed from coolers on August 2, 1991. Weight change = weight before simulated shipping - weight after simulated shipping.
^xSignificance determined using Duncan's Multiple Range Test, 5% level. Means in the same column with the same letter are not significantly different.

Table 3. Effects of medium moisture level during simulated shipping on plant grade of Dracaena fragrans 'Massangeana' after 6 weeks indoors^z. Exp. 2.

^zOn July 26, 1992 plants were stored for 2 weeks in dark coolers to simulated shipping conditions. On August 10, 1992, plants were removed from coolers and placed indoors under 125 ft-c until September 18, 1992.
^yPlants were last watered on the day simulated shipping was initiated, or 1, 4, 7 or 10 days before simulated shipping began.
^xPlants were graded based on a scale of 1 = dead, 2 = poor quality, unsalable, 3 = fair quality, salable, 4 = good quality and 5 = excellent quality.
^wSignificance determined using Duncan's Multiple Range Test, 5% level. Means in the same column with the same letter are not significantly different.