Acclimatization Revisited

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University of Florida, IFAS
Central Florida Research and Education Center - Apopka
CFREC-Apopka Research Report RH-90-2

C.A. Conover and R.T. Poole*

Ficus benjamina and Ficus retusa 'Nitida' are among the foliage plants that respond most positively to acclimatization. Over the years we have found that production of these plants under specific shade levels [generally 50 to 70% shade in Florida (approximately 3500 to 5000 ft-c)] resulted in trees best suited for interiorscape use. Production under less than 50% shade produces trees with increased potential for leaf drop. In contrast, those grown under more than 70% shade have reduced food reserves and therefore decreased ability to replace leaves lost through mismanagement during shipping and installation (although they often drop very few leaves after production under 70-80% shade if handled correctly).

Interiorscapers have not fully accepted Ficus grown entirely under shade because they often desire a heavy, thick trunk and dense foliage which occurs only under higher light levels. Our research has shown that thick foliage is a sign of a nonacclimatized tree with the potential to lose most of the leaves in the center of the canopy when placed indoors. The beauty of thick trunks lies in the eye of the beholder, but such trunks cannot be produced on trees grown entirely under shade. However, trunk size on trees grown under shade is better when they are properly spaced and grown where some wind movement of the tree occurs (movement causes increased thickening of trunks).

Producers of the Ficus species under discussion have developed a system which involves growing trees in full sun until they achieve the desired height and trunk diameter, then moving them to shade conditions. Although this system has been acceptable, no comparison has been available for trees produced entirely under shade conditions versus those grown in sun and then moved to shade. We conducted several experiments at the Central Florida Research and Education Center - Apopka, FL to compare such trees under interior environments.

Trees grown under a 63% shade level have large, flat, dark green leaves widely spaced along branches. Conversely, sun-grown trees have smaller, lighter green leaves closely spaced along branches. Movement of sun-grown plants from full sun to 63% shade results in development of trees with both types of leaves; shade leaves on new growth and sun leaves in the old canopy center. Depending on the duration of time under shade, a sun-grown plant can have mostly sun leaves or mostly shade leaves. Differences in the appearance of plants maintained in full sun and then switched to 63% shade can vary, but relate to length of time under each condition (Table 1). Shade-grown plants in this experiment were the tallest and had the greatest leaf area and best appearance. Even eight weeks in 63% shade was insufficient to overcome the partial appearance of sun-grown foliage on these small trees, although spending over one-half of the 10 weeks in the shade did improve the appearance of the plants over those that spent less than one-half of the time in 63% shade. In another experiment, effects of moving both small (2 gallon) and larger (4 gallon) Ficus benjamina trees from sun to shade to acclimatize them was compared to determine whether size was a factor in acclimatization. The changes from the previous research were an increase in duration of the acclimatization period (from 10 to 16 weeks) with 4 week sun/shade treatment intervals, two sizes of plants, and movement of the plants into interior rooms after acclimatization treatments were completed. Overall plant quality was somewhat better for sun-grown plants in this experiment than in the previous experiment, but plants that spent at least one-half the 16 weeks in the shade were still better than those that spent less than one-half the time in the shade (Table 2). Leaf drop after placement indoors (125 ft-c and 78°F) was related to time in full sun. Both small and large trees that were sun/shade conversions lost more leaves than those grown entirely under shade. Most leaves were lost from the center of the canopy and were mainly those produced in full sun. The percentage of leaves lost from small and larger trees based on total number of leaves was similar.

Lastly, an experiment was designed to compare the response of both Ficus benjamina and Ficus retusa 'Nitida' to sun/shade conversion. The interval for sun/shade treatments was increased to eight weeks to determine whether greater differences between treatments could be observed. Eight weeks of full sun followed by sixteen weeks of 63% shade produced plants of both species that were essentially the same quality as those grown in shade for the entire 24 weeks. The similarity in quality was also evident in the interior environment (Table 3), although leaf drop was still greater for those plants produced for some time under full sun. These data provide additional information on acclimatization of Ficus benjamina and F. retusa 'Nitida' in that not only is appearance of shade-grown trees better, but they drop considerably fewer leaves under an interior environment than converted trees drop. However, the longer the sun-grown trees are held under shade, the more complete the transformation to an acclimatized shadegrown tree. At least in small trees, four months of acclimatization is necessary to gain the appearance of an acclimatized tree, but it is not sufficient to retard loss of sun leaves. Based on these data we suspect that, depending on tree size, periods of four months to a year under shade are necessary to minimize leaf drop.

*Center Director and Professor and Professor, Plant Physiology, respectively, Central Florida Research and Education Center, 2807 Binion Road, Apopka, Florida 32703-8504

^Z1 = poor; 3 = salable; 5 = excellent

1. ^Z1 = poor; 3 = salable; 5 = excellent.
   ^YTotal of leaves lost during shipping period (stored in coolers at 65°F for 3 weeks) as well as in the interior environment (l month).
   ^XFicus in 2 gallon containers averaged 800 leaves/plant and those in 4 gallon containers averaged 2000 leaves/plant before shipping was initiated.

1. ^Z1 = poor; 3 = salable; 5 = excellent.
   ^YAverage total leaf drop during shipping (stored in coolers at 65°F for 2 weeks) as well as in the interior environment (2 months).