The publications in this collection do
not reflect current scientific knowledge
or recommendations. These texts
represent the historic publishing
record of the Institute for Food and
Agricultural Sciences and should be
used only to trace the historic work of
the Institute and its staff. Current IFAS
research may be found on the
Electronic Data Information Source
site maintained by the Florida
Cooperative Extension Service.
Copyright 2005, Board of Trustees, University
Acclimatization of Tropical Foliage Plants
Charles A. Conover and Richard T. Poole
University of Florida, IFASi Li JZ
ARC-Apopka Research Reportl
According to Webster, "acclimatization is the' climatic adaptation of
n organism, especially a plant, that has been move fFtSa- hwb.q lpgetnt".
several years research has shown that acclimatization prior to placement
.ndoors is beneficial for some plants. The length of the acclimatization
period, as well as the type of acclimatization required for plants growing
under different climatic and cultural conditions varies. However, recent
,ork indicates that it is possible to acclimatize plants in the production
.rea, provided plants are grown under specified light intensities and on
controlled nutritional and watering regimes. Factors known to be important
production or acclimatization under shade, correct nutrition combined
with reduction near the end of the crop cycle, and watering procedures and
soil media that allow production of extensive root systems. A discussion
of factors important in acclimatization follows, along with suggestions
that will provide high quality tropical plants for interiors.
Adaptation of plants to varying light intensities has been known for
years. The adaptation takes several forms, and under high light, produces
smaller thicker foliage, stacking of chloroplasts in cells and vertical
orientation of grana within chloroplasts. These are protective mechanisms
to prevent injury to cell components from high light intensities, but reduce
the ability of plants to produce carbohydrates (food) through photosynthesis.
Although this presents no problem while the plant is under high light in
the production area, movement of a plant grown under high light intensities
to an interior location will present problems because of the plants com-
pensation point. "Compensation Point" is that point at which energy (food)
required by the plant in respiration is equal to the amount produced by
photosynthesis. A plant grown under high light intensity has a higher com-
pensation point than it would have if grown in heavy shade. Therefore, even
though 100 foot-candles of light may be sufficient for a shade grown plant
when moved indoors, if the plant were grown in the sun, 200 foot-candles may
not be sufficient.
Acclimatization may take several forms. Light acclimatization has
been considered to be conversion of a high light grown plant to low light
intensities of interior environments. Such a conversion can be made with
most plants which will provide the consumer with a plant better adapted to
survival indoors. Research at the Agricultural Research Center, Apopka has
shown that with Ficus benjamina, placement under 80% shade for 5 weeks
reduced leaf drop by 50% when plants were subsequently placed under interior
conditions. Additional acclimatization for 10 or 15 weeks was also benefi-
cial, but not of the magnitude cf the first 5 weeks. Generally, similar
results have been found with Brassaia actinophylla, but leaf drop was not
Several problems have been noted with acclimatization of sun grown
Ficus and B assaid that influence consumer acceptance. Research has yet to
show whether sun grown leaves can be converted to shade leaves, and if so,
measure efficiency of such a leaf. Observations to date, with Ficus @
benjamin and Ficus nidita indicate little conversion, but rather production
f new shade foliage combined with conversion of immature foliage on plants
O ime of placement under shade. After placement indoors, such plants drop
ost of the original sun grown foliage within a few months, while foliage
produced under shade remains on the plant. Acclimatized sun grown Ficus
will have present both small thick light green foliage produced in full sun,
and large, thin dark green foliage near the branch tips produced in shade.
Such plants will usually survive interior use provided they receive 75 to
100 foot-candles of light for 10 to 12 hours a day, 7 days a week. Shade
grown foliage is more efficient indoors, because leaves are thinner, larger,
chloroplasts are dispersed within cells and grana have a horizontal
orientation. These mechanisms enable shade grown leaves to absorb more of
;he incoming light energy, which allows them to phytosynthesize more
efficeintly under low light conditions. Brassaia grown under full sun have
*ht green foliage with short petioles, but when placed indoors, petiole
length increases by 50 to 100% and leaves become dark green. This results
in a plant with reduced esthetic appeal.
Whether plants are acclimatized or not, sufficient intensity, duration
and quality of indoor lighting will go a long way toward maintaining plant
quality. Increased light duration can reduce detrimental effects of low
light levels provided the amount supplied is above the compensation..point.
Therefore, the minimum required light intensity depends on where the plant
was grown. For sun grown plants, the minimum suggested interior light
intensity is 150 foot-candles with a 10 to 12 hour duration, 7 days a week
while with shade grown or acclimatized plants, 75 to 100 foot-candles with
a 10 to 12 hour duration 7 days a week will be satisfactory. Many other
lighting regimes are possible, but depend on compensation points for
Light quality is important for plant growth, but little growth is
desired in most interior situations. Normally, one should supply light in
both the blue, 430 to 470 mu (millimicrons) and red, 650 to 700 mu wave-
lengths. However, excellent quality tropical foliage plants can be maintain-
ed with predominately blue light, such as obtained from fluorescent lighting.
A passing note seems necessary on light acclimatization, in that many
people seem to lack knowledge on how most foliage plants are produced. In
California, Florida and Texas approximately 85% of plants are shade grown.
Therefore, only 15% of plants are sun grown, and some of these are acclima-
tized before shipment. Most commonly, the only plants grown in full sun are
Ficus, Brassaia, Dracaena marginata, several palms, Araucaria and Sansevieria.
Soil Medium Acclimatization
Nutrition Volumes have been written on plant nutrition, and most
tropical plant producers supply sufficient fertilizer to obtain maximum
growth and quality. However, nutrition is directly related to acclimatizati-
zation, because a plants need for fertilizer decreases by a factor of 10 or
more after placement indoors. For example, good quality and growth rate
can be obtained with Chrysalidocarpus lutescens (Areca palm) when a
fertilizer rate equivalent to 7500 lb of 20-20-20 is applied/acre/yr.
However, good indoor maintenance can be obtained with 1/10th or less that
amount. The problem then, is what happens to a plant after it is removed
from the production area where higher nutrition is necessary for growth to
kow light interiors where much lower levels are desired. Most commonly, on
sensitivee plants such as palms, dracaenas, schefflera and greenhouse grown
foliage a rapid loss in quality occurs due to excess fertilizer (high
soluble salts). Symptoms are burned foliage, general loss of color, foliage
drop and in severe cases, plant death.
Nutritional acclimatization may take several forms, but the need and
extent depends on how the plant was grown. The first question that may be
*sed is whether the producer used the correct fertilizer rate, since some
excess fertilizer may be applied without producing toxicity symptoms (hidden
toxicity). Another consideration that enters the picture is the light
intensity the plant was grown under, since the higher the intensity the more
fertilizer needed to produce quality. The problem facing the purchaser is
that unless plants are nutritionally acclimatized there is a good chance
damage may occur.
The best way to acclimatize plants nutritionally is (1) stop addition
of fertilizer, (2) leach soil heavily with at least 6 inches of water and
(3) supply several hundred foot-candles of light. To date, research has
shown leaching and use of .lower fertilizer levels are beneficial, but the
length of time before placement indoors has not been determined.
SSoil Moisture Several factors influence water uptake of plants under
interior environments, including size of root systems or root:shoot ratio,
oxygen level present in the growing medium, water holding capacity of the
*medium and the microclimate which includes humidity, air movement and
During acclimatization root system size can be improved by reducing
nutrition and lengthening the watering interval. This method reduces top
growth while root growth continues with a subsequent increase in root:shoot
ratio. This will also harden foliage so it will be less likely to wilt
under low humidity situations.
Several experiments conducted over the last 2 years indicate that
acclimatization is possible in the production area provided producers change
production systems. A major change would be to produce all plants intended
for interior use under shade of at least 40% and up to 80% in some cases.
This change should not increase costs greatly because growth rate is equal
or greater than full sun production, fertilizer costs are reduced and pest
control (diseases, insects and weeds) are about equal. Production under
shade would produce shade leaves which are necessary on plants to be used
indoors, and reduced fertilizer rates would reduce need for soil acclima-
tization. Recent work on Ficus benjamin has shown that good quality,
larger than full sun grown plants, can be produced in 80% shade, with
fertilizer rates 1/2 that needed for full sun production. Such plants need
no acclimatization provided the proper soil mixture is utilized, so that
extensive root systems form during production. Acclimatization during
production can also be accomplished on small potted plants such as
Aphelandra. As all Aphelandra is grown under heavy shade, light acclimat-
ization is unnecessary. However, the problem with Aphelandra has been
excessive fertilizer application. Research now completed shows that
reduction in fertilizer rate combined with leaching prior to shipment
provides consumers a plant that will last for months rather than weeks.
Whenever a foliage plant does poorly indoors, it is usually blamed on
the producer, who supplied a nonacclimatized plant. However, there are a
number of factors over which the producer has no control that may affect
any plant, acclimatized or not. Some of the most important are mentioned
Light Exclusion During shipping and/or holding, foliage plants are
frequently left in boxes or other dark areas. Many foliage plants will
start to lose foliage after 7 days of such treatment and after 10 days will
be severely injured. Periods longer than 14 days almost always result in
Shine Compounds Application of shine compounds to foliage plants may
reduce their ability to photosynthesize and may injure tissue of a number
species. If these materials are used, they should not be applied on a
Pesticides Unfortunately, on arrival some foliage plants may be
found infested with pests. These need to be removed since mites especially
may cause injury to foliage under low humidity conditions. However, selec-
tion of the proper pesticides is important, since phytotoxicity may occur
on many species of foliage from several common pesticides.
Fluoride Tipburn as well as chlorosis may occur on plants of the
genus Chlorophytum, Cordyline, Dracaena, Maranta and Yucca from fluoride in
the soil water complex. This can be controlled by increasing pH of the
soil medium or using distilled or deionized water.
Cold Damage A number of tropical foliage plants are injured when
#ected to cool (40 to 450F) temperatures or watered with cold water.
Plants particularly susceptible to low temperatures are Aglaonema,
Dieffenbachia and Fittonia. Some other foliage plants that develop spots
on foliage from cold water are Philodendron, Syngonium and Sansevieria.
Air Pollution Ethylene, carbon monoxide, sulphur dioxide and several
other air pollutants can injure foliage plants. Most commonly injury occurs
during shipping when polluted air is circulated through the truck. Symptoms
exhibited by injured plants usually include dropping foliage or development
of a dull off-color appearance.
Watering Practices Many plants are killed by overwatering. Wilted
plants will almost always survive if watered before death occurs, however,
once roots are killed because of overwatering, the plant rarely survives.