Decorative Oak Leaves in Pots of 'Camille' Dieffenbachia Damage Plants During Simulated Shipping and Storage

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C.A. Conover, Ph.D.*

University of Florida/IFAS
Central Florida Research and Education Center
CFREC-Apopka Research Report RH-95-1

Many different kinds of decorative materials can be added to foliage plant containers prior to shipping to dress-up plants for a particular holiday or promotion. Theme decorations can increase plant sales but precautions need to be taken when decorative materials are added prior to shipping or storing foliage plants. Air movement around plants is usually limited during shipping and storage, and free moisture may occur when foliage plants are moved from production greenhouses to markets, especially when plants are sleeved and boxed for transit.

During this time, concentrations of certain chemicals used in the manufacture of decorative materials could build up to levels high enough to damage foliage of sensitive species. Some foliage plants have been shown to be sensitive to ethylene during shipping and storage (Marousky and Harbaugh, 1978; Marousky and Harbaugh, 1982; Wolthering, 1987). Dieffenbachia 'Compacta' placed in a simulated interior environment was damaged when mercury, a paint additive used to control mildew, vaporized from recently painted surfaces (Poole and Conover, 1987).

In late September, 1993, leaves of dieffenbachia plants that had been decorated with preserved oak leaves, sleeved, and then shipped from a local nursery to retail outlets, were damaged during shipment. The nursery (Vaughn Inc., P.O Box 1737, Sanford, FL 32772) then donated to us a large supply of preserved oak leaves they had purchased from three different florist supply firms. The oak leaves were attached to twigs, about six to eight leaves per twig. The following test was conducted to determine if dyed oak leaves, used for decorative effect during Autumn, could have a harmful effect on 'Camille' dieffenbachia during shipping and storage.

Excellent quality Dieffenbachia maculata 'Camille' ('Camille' dieffenbachia), of salable size, grown in 6-inch plastic tub pots were used for the experiment. 'Camille' was grown using Fafard #4 growing medium (Fafard of Florida, Inc., Apopka, FL 32703) amended with up to 7.5 lb/yd3 dolomite and 1 lb/yd3 Micromax (The Scotts Company, 6656 Grantway, Allentown, PA 18106). Plants had been grown from liner to finished size in a greenhouse where air temperature ranged from 65 to 90°F and maximum light intensity was about 2000 ft-c. Liquid fertilizer made from stock solutions was applied once per week during production. Plants had been fertilized at a rate of 1833 lb N/A/yr, with 50% N from NH₄ and 50% N from NO₃.

This experiment began on October 7, 1994, when preserved oak leaves manufactured by florist supply company A, B or C were placed in pots containing 'Camille' dieffenbachia, 1, 2 or 3 twigs per pot. Plants were sleeved using standard brown paper plant sleeves, boxed and placed in dark coolers where air temperature was maintained at 65°F to simulate shipping conditions. On October 11, 1994, after four days simulated shipping, boxed plants were moved to a room where light intensity was about 150 ft-c and air temperature was about 70°F to simulate the brief holding period plants commonly experience at busy retail outlets. On October 13, 1994, 'Camille' dieffenbachia were removed from boxes, unsleeved and moved back to the production greenhouse.

One day later, the number of damaged leaves per pot was counted and severity of damage rated. Overall severity of damage was rated based on a scale of 0 = no damage; 1 = little foliage damage, excellent overall plant, quality not affected; 2 = damage readily visible, plant quality reduced from excellent to good; 3 = damage reduced plant quality to fair but salable; 4 = damage reduced plant quality to poor, plant not salable; 5 = very severely damaged, plant not salable. Damage appeared as water-soaked, collapsed and browning tissue.

Results

'Camille' dieffenbachia foliage is sensitive to mechanical injury so minor foliage damage is common after shipping and handling. As would be expected, a few damaged leaves were found on the control group shipped without the decorative oak leaves included in their containers. Compared to the control, more damage and greater severity of damage was found on foliage of 'Camille' shipped with treated oak leaves from any of the florist supply sources (Table 1). 'Camille' dieffenbachia showed a greater number of damaged leaves when the number of twigs per pot was increased from l to 2 than when number of twigs was increased from 2 to 3 (Tables 2 through 4).

Increasing the number of type B oak twigs per 6-inch pot did not cause an increase on severity of foliage damage (Table 3). However, when A or C oak leaves were used, severity of damage increased slightly when number of twigs per pot increased (Tables 2 and 4). The major damage occurred when oak leaves touched 'Camille' foliage or were in very close proximity. The fact that plants were both sleeved and boxed probably compounded the problem because it increased the potential for leaf contact.

Conclusions

Because treatments used to preserve and dye oak leaves are proprietary, specific chemical treatments used on the oak leaves utilized for this experiment are unknown. In discussing these results with others, knowledgeable sources mentioned glycerine, formaldehyde, magnesium and sodium chloride as chemicals possibly used in the preservation process.

In summary, although decorative additions can increase sales, growers need to be very careful about what they place in pots, boxes, etc. along with their plants because contact damage or damage from gases such as ethylene may result.

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

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Table 1. Number of damaged leaves and severity of damage on 'Camille' dieffenbachia affected by source of decorative oak leaves added to containers prior to simulated shipping and storage.

^zNumber of damaged leaves per tub was counted on October 14, 1994.
^yDamage severity was determined based on the scale 0 = no damage, 1 = little foliage damage, excellent overall plant, quality not affected, 2 = damage readily visible, plant quality reduced from excellent to good, 3 = damage reduced plant quality to fair but salable, 4 = damage reduced plant quality to poor, plant not salable, 5 = very severely damaged, plant not salable.
^xMean separation in columns by Duncan's multiple range test.

Table 2. Effects of number of oak leaf twigs per ,not supplied by florist supply firm A on foliage damage on 'Camille' dieffenbachia after four days simulated shipping and two days simulated storage.

^zNumber of damaged leaves per plant was counted on October 14, 1994.
^yDamage severity was determined based on the scale 0 = no damage; 1 = little foliage damage, excellent overall plant, quality not affected; 2 = damage readily visible, plant quality reduced from excellent to good; 3 = damage reduced plant quality to fair but salable; 4 = damage reduced plant quality to poor, plant not salable; 5 = very severely damaged, plant not salable.
^xns, **; Nonsignificant or significant at P = 0.01, respectively.

Table 3. Effects of number of oak leaf twigs per pot supplied by florist supply firm B on foliage damage on 'Camille' dieffenbachia after four days simulated shipping and two days simulated storage.

^zNumber of damaged leaves per plant was counted on October 14, 1994.
^yDamage severity was determined based on the scale 0 = no damage; 1 = little foliage damage, excellent overall plant, quality not affected; 2 = damage readily visible, plant quality reduced from excellent to good; 3 = damage reduced plant quality to fair but salable; 4 = damage reduced plant quality to poor, plant not salable; 5 = very severely damaged, plant not salable.
^xns, **; Nonsignificant or significant at P = 0.01, respectively.

Table 4. Effects of number of oak leaf twigs per pot supplied by florist supply firm C on foliage damage on 'Camille' dieffenbachia after four days simulated shipping and two days simulated storage.

^zNumber of damaged leaves per plant was counted on October 14, 1994.
^yDamage severity was determined based on the scale 0 = no damage; 1 = little foliage damage, excellent overall plant, quality not affected; 2 = damage readily visible, plant quality reduced from excellent to good; 3 = damage reduced plant quality to fair but salable; 4 = damage reduced plant quality to poor, plant not salable; 5 = very severely damaged, plant not salable.
^xns, **; Nonsignificant or significant at P = 0.01, respectively.

References

1. Marousky, F.J. and B.K. Harbaugh. 1978. Deterioration of foliage plants during transit. Foliage Digest 3(7):9-14.
2. Marousky, F.J. and B.K. Harbaugh. 1982. Responses of certain flowering and foliage plants to exogenous ethylene. Proc. Fla. State Hort. Soc. 95:159-162.
3. Poole, R.T. and C.A. Conover. 1987. Response of foliage plants to commercial interior paints. Foliage Digest 10(1):4-5.
4. Wolthering, E.J. 1987. Effects of ethylene on ornamental pot plants: a classification. Scientia Hortic. 31:283-294.