Citation
Commercial forcing of caladiums

Material Information

Title:
Commercial forcing of caladiums
Creator:
Harbaugh, B. K.
Place of Publication:
Gainesville, Fla.
Publisher:
Florida Cooperative Extension Service, Institute of Food and Agricultural Sciences, University of Florida,
Language:
English

Subjects

Subjects / Keywords:
Agriculture ( LCSH )
Farm life ( LCSH )
Farming ( LCSH )
University of Florida. ( LCSH )
Agriculture -- Florida ( LCSH )
City of Gainesville ( local )
Tubers ( jstor )
Roses ( jstor )
Potted plants ( jstor )
Spatial Coverage:
North America -- United States of America -- Florida

Notes

Funding:
Florida Historical Agriculture and Rural Life

Record Information

Source Institution:
Marston Science Library, George A. Smathers Libraries, University of Florida
Holding Location:
Florida Agricultural Experiment Station, Florida Cooperative Extension Service, Florida Department of Agriculture and Consumer Services, and the Engineering and Industrial Experiment Station; Institute for Food and Agricultural Services (IFAS), University of Florida
Rights Management:
All rights reserved, Board of Trustees of the University of Florida

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Circular 621


Commercial Forcing of Caladiums

B. K. Harbaugh and B. O. Tjia


Florida Cooperative Extension Service / Institute of Food and Agricultural Sciences
University of Florida, Gainesville / John T. Woeste, Dean for Extension







COMMERCIAL FORCING OF CALADIUMS

B. K. Harbaugh and B. O. Tjia*


Caladiums have many uses in the floricultural industry. They are
commonly sold as potted plants in the florist trade, as tubers for use
in landscapes or home gardens, or as bedding plants for late spring
or early summer.
This circular addresses factors that are essential for successful forc-
ing of caladiums as potted plants. The information presented is a
summary of research by the senior author as well as consolidation
and interpretation of research by various researchers cited in the
related literature section.


Cold Injury
Just as poor quality seeds, improper germination temperature and
use of "abused" seedlings can lead to disastrous results for seed-
grown potted plants, improper handling of caladium tubers at any
stage from harvesting through potting will increase production time
and diminish the quality of finished plants.
Caladiums are tropical plants and tubers should not be stored, ship-
ped, or handled at temperatures below 70 F. Once tubers are cold
injured, the damage is irreversible. The extent of the cold injury
depends on the temperature and duration of exposure. For exam-
ple, injury caused by exposure to 60 OF for four weeks in storage may
be similar to injury from exposure at 50 F for only five to 10 days,
while one to two hours at these temperatures may not cause any
injury. Cold injured tubers do not sprout as quickly, have less breaks,
are more prone to disease, and do not grow as fast as properly han-
dled tubers. Cold injured tubers are rubbery, while properly han-
dled tubers are firm.
Growers, whose profits can be lost by planting cold injured tubers,
can learn to recognize cold injured tubers by placing 'Frieda Hem-
pie' and 'Candidum' tubers in a refrigerator and comparing them
weekly for six weeks to nonrefrigerated tubers. These two cultivars
will express the range of symptoms caused by cold injury sustained
during the six weeks of refrigeration.



*B. K. Harbaugh is Associate Professor at the Gulf Coast Research and Education
Center, Bradenton, and B. O. Tjia is Associate Professor in the Ornamental Hor-
ticulture Department, IFAS, University of Florida, Gainesville.

































Fig. 1 Fancy-leaved caladium


Fig. 2 Lance-leaved caladium


2








Tuber Storage
Tubers stored at least six weeks at 70-800F sprout more rapidly
than those stored less than six weeks, while vigor rapidly decreases
with storage greater than 16 weeks. Tubers which have not been
stored six weeks may take eight weeks from planting just to begin
to sprout and an additional four weeks to become marketable. Tubers
stored at 70 F within the six- to 16-week ideal period will sprout
and be marketable in only four to eight weeks from planting. Thus,
growers should request information from suppliers concerning the
date the tubers were dug as well as the storage and shipping
temperatures.
If a grower purchases tubers which have not been stored six weeks,
then he should store them the additional weeks at 70 F. Storage
rooms require a minimum of space, energy and associated costs to
maintain at 700F when compared to the mistake of tying up
greenhouse space and associated costs for an extra five to six weeks
with dormant potted tubers. Storage rooms should have humidity
control (75% RH) and air exchange to prevent build-up of any gases.



Cultivars

There are two distinct types of caladiums, fancy-leaved (Fig. 1)
and lance-leaved (Fig. 2). Fancy-leaved caladiums have broad heart-
or arrow-shaped leaves, grow taller than lance-leaved types, and are
borne on erect petioles. Lance-leaved caladiums have narrow,
lanceolate leaves on short petioles, producing a more compact or
prostrate plant. Generally, they produce more leaves than fancy-
leaved caladiums and are ideal for hanging baskets as well as 4-inch
to 5-inch pots.
Although there are over 100 cultivars of caladiums grown by
Florida tuber producers, many of the cultivars should not be grown
as a potted plant since they have characteristics resulting in a poor
quality finished product. Table 1 is a descriptive list of 35 caladium
cultivars commonly sold as tubers for pot plant production and an
evaluation of their growth characteristics and value when forced
as a pot plant. These cultivars were forced with the center bud in-
tact (i.e. not scooped) and evaluated in a relatively high light inten-
sity (25% shade or 6-7,000 ft. c.), and thus, if forced using different
production methods, the "pot value" of some of the listed cultivars
might be significantly higher.
The following additional 10 cultivars have unusual or distinct
characteristics and were rated 3.0 or above for pot value (1-5 rating
scale, 5 = excellent), but availability may be limited since tubers are








Tuber Storage
Tubers stored at least six weeks at 70-800F sprout more rapidly
than those stored less than six weeks, while vigor rapidly decreases
with storage greater than 16 weeks. Tubers which have not been
stored six weeks may take eight weeks from planting just to begin
to sprout and an additional four weeks to become marketable. Tubers
stored at 70 F within the six- to 16-week ideal period will sprout
and be marketable in only four to eight weeks from planting. Thus,
growers should request information from suppliers concerning the
date the tubers were dug as well as the storage and shipping
temperatures.
If a grower purchases tubers which have not been stored six weeks,
then he should store them the additional weeks at 70 F. Storage
rooms require a minimum of space, energy and associated costs to
maintain at 700F when compared to the mistake of tying up
greenhouse space and associated costs for an extra five to six weeks
with dormant potted tubers. Storage rooms should have humidity
control (75% RH) and air exchange to prevent build-up of any gases.



Cultivars

There are two distinct types of caladiums, fancy-leaved (Fig. 1)
and lance-leaved (Fig. 2). Fancy-leaved caladiums have broad heart-
or arrow-shaped leaves, grow taller than lance-leaved types, and are
borne on erect petioles. Lance-leaved caladiums have narrow,
lanceolate leaves on short petioles, producing a more compact or
prostrate plant. Generally, they produce more leaves than fancy-
leaved caladiums and are ideal for hanging baskets as well as 4-inch
to 5-inch pots.
Although there are over 100 cultivars of caladiums grown by
Florida tuber producers, many of the cultivars should not be grown
as a potted plant since they have characteristics resulting in a poor
quality finished product. Table 1 is a descriptive list of 35 caladium
cultivars commonly sold as tubers for pot plant production and an
evaluation of their growth characteristics and value when forced
as a pot plant. These cultivars were forced with the center bud in-
tact (i.e. not scooped) and evaluated in a relatively high light inten-
sity (25% shade or 6-7,000 ft. c.), and thus, if forced using different
production methods, the "pot value" of some of the listed cultivars
might be significantly higher.
The following additional 10 cultivars have unusual or distinct
characteristics and were rated 3.0 or above for pot value (1-5 rating
scale, 5 = excellent), but availability may be limited since tubers are












CULTIVARS
Fancy leaf types
Aaron
Candidum
Candidum, Jr.
Carolyn Whorton
Dr. Groover
Fannie Munson
Festivia
Frieda Hemple
Irene Dank
Itcapus


John Peed
June Bride
Kathleen
Lord Derby
Miss Chicago
Mrs. Arno Nehrling
Mrs. F. M. Joyner

Pink Beauty
Pink Cloud
Postman Joyner

Red Flash
Rosebud (BH)

Scarlet Pimpernell
Tom Tomlinson
White Christmas


Lance-leaf types
Caloosahatchee Medium Rose fringed veins
Clarice Dark Light pink spots
Jackie Suthers Dark White interveins
Lance Whorton Medium Medium pink spots
Pink Gem Medium White interveins
Pink Symphony Medium Light pink and white spots
Red Frill Dark Red with small white spots
Sea Gull Medium White speckled
Sunset Medium Dark rose spots
White Wing Medium White speckles

Table 1. A descriptive list of 35 exceptional caladium cultivars commonly sold
as tubers for pot plant production and an evaluation of their suitabil-
ity as potted plants.

produced by only a few growers: Dr. T. L. Meade, Fire Chief, Gypsy
Rose, Marie Moir, Miss Muffet, Mumbo, Poecile Anglais, Sunburst,
Torchy, and White Queen.
Many of the cultivars listed in Table 1 and cultivars bred especial-
ly for pot use (such as the Honey-BunchTM series) are also available


Margin
Light
Dark
Dark
Dark
Light
Dark
Medium
Medium
Dark
Dark

Medium
Medium
Light
Medium
Medium
Dark
Dark

Dark
Medium
Dark

Dark
Light

Light
Medium
Medium


LEAF COLORS
Center
Creamy white
White interveins
White interveins
Large pink spots
Medium rose spots
Dark rose
Dark rose spots
Red-rose
Medium red
Dark rose with
rose spots
Dark rose-red
White with white spots
Medium pink
Light pink spots
Dark rose spots
White with pink spots
Medium rose with
rose spots
Dark pink spots
Dark pink spots
Dark rose with
red spots
Rose with pink spots
Medium rose with
green specks
Rose-red blotches
Dark red-rose spots
White blotches











POTTED PLANT CHARACTERISTICS
LEAF COLORS Leaves Plant height Leaf size (in.) Pot
Main vein (No.) (inches) Length Width value


3.7
3.8
4.5
3.1
3.4
3.0
3.1
4.2
4.1
3.2


8.2 4.9 3.4
5.2 3.8 3.1

6.3 4.0 2.4
5.8 3.3 4.2
7.3 4.8 4.2


Cream 27 10 6.6 3.7 4.0
Dark Pink 22 11 8.1 4.7 3.8
Light Green 26 9 5.7 5.3 4.0
Dark Red 22 10 6.5 4.4 2.9
Dark Pink 25 9 5.7 3.2 4.4
Medium Green 22 10 6.5 3.8 3.2
Dark Red 41 7 6.3 3.6 4.5
Medium Green 27 11 6.1 3.9 3.6
Dark Green 19 6 6.2 3.8 3.2
Pale Rose 24 10 6.1 3.7 4.6
x Value of 1 was poor; 3 was acceptable; and 5 was excellent
Y Results from evaluation in 1981 and 1982; Jumbo tubers forced in 6-inch pots; 6000-7000
ft c; not scooped (see cultivar section)
z Abstracted from Wilfret, G. J. and G. T. Hurner, Jr. 1982. Proc. Fla State Hort. Soc. 95:190-194

as tissue cultured explants or plugs. Choice of a particular cultivar
should take into account plant characteristics in the production en-
vironment, their expected use (indoors or as a bedding plant), and
the capability of the grower to modify the production environment
to suit the requirements for optimum growth of a particular cultivar.


Green
Green
Green
Dark Red
Medium Rose
Dark Rose
Dark Green
Red-rose
Dark Red
Dark Red


14
18
21
13
27
14
22
22
17
15


14
14
10
15
13
15
13
13
13
11


Dark Rose
Light Green
Medium Pink
Dark Green
Dark Rose
Dark Red
Rose-red

Medium Rose
Light Pink
Dark Red

Dark Rose
Dark Rose

Dark Red
Burgundy
Dark Green








Tuber Size
Both fancy- and lance-leaf caladium tubers are graded according
to their diameter as follows:
Super Mammoth 41/2 inches or larger
Mammoth 31/2 to 41/ inches
Jumbo 21/ to 3/2 inches
#1 11/2 to 21/2 inches
#2 3/4 to 11/2 inches
Choice of tuber size for a given pot size is critical. One mammoth
tuber per 6-inch pot, one jumbo tuber per 5-inch pot, one No. 1 tuber
per 31/2- or 4-inch pot, one No. 2 tuber per 3-inch pot, or one No.
2 tuber per cell of a six-pack produces a marketable plant quickly.
Many growers think they can "get by" using tubers a grade smaller
than normally required for a fast turnover of a quality plant. To il-
lustrate shortcomings associated with cheating on tuber size, if one
uses a No. 2 tuber in a 4-inch pot instead of a No. 1 tuber, the first
leaves of the initial sprouts from the smaller tuber will not yield a
plant with the proper pot-to-shoot ratio. Thus, two, three or even
four weeks' extra greenhouse time would be required to allow the
plant to reach proper marketable size.




Scooping Center Bud Removal
Tubers with the center or dominant bud removed (scooped) pro-
duce more leaves initially than tubers planted intact and upright (Fig.
3) and sprout faster than inverted tubers. Scooping eliminates the
dominance of the center bud, giving the other buds a better start.
This will result in a fuller pot plant. Thus, scooping is recommended
for most cultivars when using a No. 1 tuber or larger, and No. 2
tubers of the taller cultivars. Most lance-leaf cultivars will not need
to be scooped as these cultivars generally have many uniform
sprouting buds (breaks) and fill the pot quickly.
Scooping requires only a 1/16- to 1/8-inch-deep cut no larger than
1/4-inch diameter since the growing point (bud) is on the surface of
the tuber. Deeper cuts increase disease potential and larger diameter
cuts may destroy desired lateral buds. Tubers may have several
similar-sized dominant buds, especially tubers in the larger grades
(Fig. 4). As a general rule for tubers with two to four similar-sized
dominant buds, the similar-sized buds are scooped. Scooping is
generally not required when five or more similar-sized dominant
buds are present on the same tuber, since all these buds will develop








Tuber Size
Both fancy- and lance-leaf caladium tubers are graded according
to their diameter as follows:
Super Mammoth 41/2 inches or larger
Mammoth 31/2 to 41/ inches
Jumbo 21/ to 3/2 inches
#1 11/2 to 21/2 inches
#2 3/4 to 11/2 inches
Choice of tuber size for a given pot size is critical. One mammoth
tuber per 6-inch pot, one jumbo tuber per 5-inch pot, one No. 1 tuber
per 31/2- or 4-inch pot, one No. 2 tuber per 3-inch pot, or one No.
2 tuber per cell of a six-pack produces a marketable plant quickly.
Many growers think they can "get by" using tubers a grade smaller
than normally required for a fast turnover of a quality plant. To il-
lustrate shortcomings associated with cheating on tuber size, if one
uses a No. 2 tuber in a 4-inch pot instead of a No. 1 tuber, the first
leaves of the initial sprouts from the smaller tuber will not yield a
plant with the proper pot-to-shoot ratio. Thus, two, three or even
four weeks' extra greenhouse time would be required to allow the
plant to reach proper marketable size.




Scooping Center Bud Removal
Tubers with the center or dominant bud removed (scooped) pro-
duce more leaves initially than tubers planted intact and upright (Fig.
3) and sprout faster than inverted tubers. Scooping eliminates the
dominance of the center bud, giving the other buds a better start.
This will result in a fuller pot plant. Thus, scooping is recommended
for most cultivars when using a No. 1 tuber or larger, and No. 2
tubers of the taller cultivars. Most lance-leaf cultivars will not need
to be scooped as these cultivars generally have many uniform
sprouting buds (breaks) and fill the pot quickly.
Scooping requires only a 1/16- to 1/8-inch-deep cut no larger than
1/4-inch diameter since the growing point (bud) is on the surface of
the tuber. Deeper cuts increase disease potential and larger diameter
cuts may destroy desired lateral buds. Tubers may have several
similar-sized dominant buds, especially tubers in the larger grades
(Fig. 4). As a general rule for tubers with two to four similar-sized
dominant buds, the similar-sized buds are scooped. Scooping is
generally not required when five or more similar-sized dominant
buds are present on the same tuber, since all these buds will develop
























A













B


Figure 3. Preparation of caladium tubers for pot plant forcing. (A) Removal (scooping) of the central or dominant bud(s) will cause
the tuber to produce many small shoots and leaves. (B) Planting the entire tuber will produce a plant with a few large leaves.








and produce a full pot quickly. However, the tall cultivars must be
scooped even with five or more buds to reduce the height of the
finished plant.


Fig. 4 Many tubers, and especially those in the larger grades, have more than one
large dominant bud or sprout. Similar-sized dominant buds should all be
removed (scooped) when tubers have one to four similar-sized dominant
buds (A). When five or more buds are present, scooping is not required on
most cultivars since similar-sized buds will grow uniformly and fill the pot
quickly (B). Tall cultivars may require scooping when five or more buds are
present to reduce the height of the finished plant.


Planting Depth
Roots emerge around each sprout on the tuber. Since sprouts are
only on the top or side of tubers, roots form primarily on the top
and sides of the tuber, not on the bottom as in bulb crops. Tubers
should be planted upright with at least 1 to 1/2 inches of soil over
the top of the tuber to ensure emerging roots are not exposed to air
or dry soil.

Soil
Soil or potting mixes and fertilization are not of major concern for
caladium forcing when compared to many potted plants. Adequate
moisture retention by the soil is the most critical problem, as
caladiums, if allowed to dry to the wilting point, may not only lose
leaves but also tend to go dormant. Once dormant, caladiums require








and produce a full pot quickly. However, the tall cultivars must be
scooped even with five or more buds to reduce the height of the
finished plant.


Fig. 4 Many tubers, and especially those in the larger grades, have more than one
large dominant bud or sprout. Similar-sized dominant buds should all be
removed (scooped) when tubers have one to four similar-sized dominant
buds (A). When five or more buds are present, scooping is not required on
most cultivars since similar-sized buds will grow uniformly and fill the pot
quickly (B). Tall cultivars may require scooping when five or more buds are
present to reduce the height of the finished plant.


Planting Depth
Roots emerge around each sprout on the tuber. Since sprouts are
only on the top or side of tubers, roots form primarily on the top
and sides of the tuber, not on the bottom as in bulb crops. Tubers
should be planted upright with at least 1 to 1/2 inches of soil over
the top of the tuber to ensure emerging roots are not exposed to air
or dry soil.

Soil
Soil or potting mixes and fertilization are not of major concern for
caladium forcing when compared to many potted plants. Adequate
moisture retention by the soil is the most critical problem, as
caladiums, if allowed to dry to the wilting point, may not only lose
leaves but also tend to go dormant. Once dormant, caladiums require








additional time to produce a marketable plant since they do not
resprout quickly. Soil mixes should contain a heavy proportion of
peat or other water-holding components to produce a soil with high
water retention characteristic (55-65 percent capillary pore space
and 4-5 percent noncapillary pore space).

Irrigation
Enough water should be applied to keep the soil at, or near, the
water holding capacity (wet!) assuming the soil has adequate air
space (noncapillary pore space see "Soil" section). Caladiums can
be watered using overhead, "spaghetti tube," or capillary mat ir-
rigation systems. However, since water conservation from 40-80 per-
cent can be achieved, the latter two methods should be considered
in areas where water is scarce or expensive. Watering can easily be
handled with a capillary mat irrigation system, and caladiums res-
pond favorably to this system.


Fertilization
A maintenance fertilizer program of 5 to 8 pounds of Osmocote(R)
14-14-14 per cubic yard of soil at planting, or a liquid fertilization
program of a 400-500 ppm N-P-K solution once a week after
sprouting will provide adequate nutrition. If tubers are to be forced
with average temperatures above 70-74 F (such as in heat tents),
then Osmocote has to be top-dressed at sprouting (1 to 11/3 teaspoons
per 6-inch pot) rather than incorporated in the soil before planting,
as top-dressing prevents premature release of nutrients from
Osmocote at these high temperatures that could otherwise result in
soluble salt injury.
Dolomite should be used to adjust the pH to a range of 5.5-6.5,
and 5 pounds per cubic yard of single superphosphate should also
be incorporated into the soil. These amendments provide sources
of calcium, magnesium and sulphur, create a favorable pH for
nutrient availability, and reduce problems of ion toxicity associated
with low pH.

Light Intensity
Light intensity in the growing area can be important for two
reasons. First, some cultivars do not develop proper color unless they
are grown in 2500 to 5000 foot candles of light. Caladiums requiring
low light include the white cultivars Candidum, White Christmas,
June Bride, and White Wing; the pink cultivars Kathleen, Fannie
Munson, and Lord Derby; and the red cultivars Frieda Hemple,








additional time to produce a marketable plant since they do not
resprout quickly. Soil mixes should contain a heavy proportion of
peat or other water-holding components to produce a soil with high
water retention characteristic (55-65 percent capillary pore space
and 4-5 percent noncapillary pore space).

Irrigation
Enough water should be applied to keep the soil at, or near, the
water holding capacity (wet!) assuming the soil has adequate air
space (noncapillary pore space see "Soil" section). Caladiums can
be watered using overhead, "spaghetti tube," or capillary mat ir-
rigation systems. However, since water conservation from 40-80 per-
cent can be achieved, the latter two methods should be considered
in areas where water is scarce or expensive. Watering can easily be
handled with a capillary mat irrigation system, and caladiums res-
pond favorably to this system.


Fertilization
A maintenance fertilizer program of 5 to 8 pounds of Osmocote(R)
14-14-14 per cubic yard of soil at planting, or a liquid fertilization
program of a 400-500 ppm N-P-K solution once a week after
sprouting will provide adequate nutrition. If tubers are to be forced
with average temperatures above 70-74 F (such as in heat tents),
then Osmocote has to be top-dressed at sprouting (1 to 11/3 teaspoons
per 6-inch pot) rather than incorporated in the soil before planting,
as top-dressing prevents premature release of nutrients from
Osmocote at these high temperatures that could otherwise result in
soluble salt injury.
Dolomite should be used to adjust the pH to a range of 5.5-6.5,
and 5 pounds per cubic yard of single superphosphate should also
be incorporated into the soil. These amendments provide sources
of calcium, magnesium and sulphur, create a favorable pH for
nutrient availability, and reduce problems of ion toxicity associated
with low pH.

Light Intensity
Light intensity in the growing area can be important for two
reasons. First, some cultivars do not develop proper color unless they
are grown in 2500 to 5000 foot candles of light. Caladiums requiring
low light include the white cultivars Candidum, White Christmas,
June Bride, and White Wing; the pink cultivars Kathleen, Fannie
Munson, and Lord Derby; and the red cultivars Frieda Hemple,








additional time to produce a marketable plant since they do not
resprout quickly. Soil mixes should contain a heavy proportion of
peat or other water-holding components to produce a soil with high
water retention characteristic (55-65 percent capillary pore space
and 4-5 percent noncapillary pore space).

Irrigation
Enough water should be applied to keep the soil at, or near, the
water holding capacity (wet!) assuming the soil has adequate air
space (noncapillary pore space see "Soil" section). Caladiums can
be watered using overhead, "spaghetti tube," or capillary mat ir-
rigation systems. However, since water conservation from 40-80 per-
cent can be achieved, the latter two methods should be considered
in areas where water is scarce or expensive. Watering can easily be
handled with a capillary mat irrigation system, and caladiums res-
pond favorably to this system.


Fertilization
A maintenance fertilizer program of 5 to 8 pounds of Osmocote(R)
14-14-14 per cubic yard of soil at planting, or a liquid fertilization
program of a 400-500 ppm N-P-K solution once a week after
sprouting will provide adequate nutrition. If tubers are to be forced
with average temperatures above 70-74 F (such as in heat tents),
then Osmocote has to be top-dressed at sprouting (1 to 11/3 teaspoons
per 6-inch pot) rather than incorporated in the soil before planting,
as top-dressing prevents premature release of nutrients from
Osmocote at these high temperatures that could otherwise result in
soluble salt injury.
Dolomite should be used to adjust the pH to a range of 5.5-6.5,
and 5 pounds per cubic yard of single superphosphate should also
be incorporated into the soil. These amendments provide sources
of calcium, magnesium and sulphur, create a favorable pH for
nutrient availability, and reduce problems of ion toxicity associated
with low pH.

Light Intensity
Light intensity in the growing area can be important for two
reasons. First, some cultivars do not develop proper color unless they
are grown in 2500 to 5000 foot candles of light. Caladiums requiring
low light include the white cultivars Candidum, White Christmas,
June Bride, and White Wing; the pink cultivars Kathleen, Fannie
Munson, and Lord Derby; and the red cultivars Frieda Hemple,








Postman Joyner, Poecile Anglais, and Dr. T. L. Meade.
Secondly, light intensities lower than 2500 foot candles will cause
undesirable stretching of petioles, oversized leaves for small pots,
and unsightly plants which fall over when handled. The dwarf
cultivars in the tissue-cultured Honey Bunch series appear to be an
exception to this rule, as they grow well at 1500 to 2500 foot candles.
Some cultivars tolerate full sun conditions and still maintain good
color. Caladiums which tolerate partial shade or full sun (light in-
tensity of 5000 to 10,000 foot candles) include the white cultivars
Candidum Junior and Seagull; the pink cultivars Carolyn Whorton,
Rosebud, Mrs. W. B. Haldeman, Pink Gem, and Lance Whorton; and
the red cultivars Fire Chief and Red Frill.

Forcing Temperature
It is important to stress again that caladiums are tropical plants
and their foliage, as well as tubers, are subject to cold injury. They
should be forced at temperatures at least averaging 70 F and not
less than 55-60 OF. Although a nighttime minimum of 55 OF for a few
hours for several nights can be tolerated, colder temperatures or
longer duration of 55-60 OF temperatures will severely injure plants.
Regrowth may occur but will be slow and usually of poor quality.
Day temperatures above 90 F are not favorable, so an optimum day
temperature range is 70-90 F, and a night-day range of 60-90 OF is
acceptable.
Many growers stack potted tubers in a confined and easily heated
area (such as heat tents) until sprouting occurs and then space plants
in the greenhouse. This method reduces heating costs and appears
satisfactory when air exchange is used to prevent build-up of gases
in the heated area. The costs of handling plants twice should be
weighed against heat savings before this method is adopted, especial-
ly if tubers have been stored properly and are ready to sprout.

Shipping
If caladium plants are to be shipped and sold in other than the pro-
duction greenhouse, then shipping and retail outlet temperatures
should be maintained near 70 F. Research has shown that storage
of plants at 55 OF for 72 hours (3 days) in the dark caused 40 percent
of the caladium leaves to abscise (turn brown and fall off), and
greater loss of leaves and chlorosis occurred with temperatures
below 55 F, even with less exposure time.
Caladiums will not tolerate the cool temperatures that may be ideal
for shipping other potted plants. Retail outlets that display plants
out-of-doors must also be aware that caladiums will not tolerate the








Postman Joyner, Poecile Anglais, and Dr. T. L. Meade.
Secondly, light intensities lower than 2500 foot candles will cause
undesirable stretching of petioles, oversized leaves for small pots,
and unsightly plants which fall over when handled. The dwarf
cultivars in the tissue-cultured Honey Bunch series appear to be an
exception to this rule, as they grow well at 1500 to 2500 foot candles.
Some cultivars tolerate full sun conditions and still maintain good
color. Caladiums which tolerate partial shade or full sun (light in-
tensity of 5000 to 10,000 foot candles) include the white cultivars
Candidum Junior and Seagull; the pink cultivars Carolyn Whorton,
Rosebud, Mrs. W. B. Haldeman, Pink Gem, and Lance Whorton; and
the red cultivars Fire Chief and Red Frill.

Forcing Temperature
It is important to stress again that caladiums are tropical plants
and their foliage, as well as tubers, are subject to cold injury. They
should be forced at temperatures at least averaging 70 F and not
less than 55-60 OF. Although a nighttime minimum of 55 OF for a few
hours for several nights can be tolerated, colder temperatures or
longer duration of 55-60 OF temperatures will severely injure plants.
Regrowth may occur but will be slow and usually of poor quality.
Day temperatures above 90 F are not favorable, so an optimum day
temperature range is 70-90 F, and a night-day range of 60-90 OF is
acceptable.
Many growers stack potted tubers in a confined and easily heated
area (such as heat tents) until sprouting occurs and then space plants
in the greenhouse. This method reduces heating costs and appears
satisfactory when air exchange is used to prevent build-up of gases
in the heated area. The costs of handling plants twice should be
weighed against heat savings before this method is adopted, especial-
ly if tubers have been stored properly and are ready to sprout.

Shipping
If caladium plants are to be shipped and sold in other than the pro-
duction greenhouse, then shipping and retail outlet temperatures
should be maintained near 70 F. Research has shown that storage
of plants at 55 OF for 72 hours (3 days) in the dark caused 40 percent
of the caladium leaves to abscise (turn brown and fall off), and
greater loss of leaves and chlorosis occurred with temperatures
below 55 F, even with less exposure time.
Caladiums will not tolerate the cool temperatures that may be ideal
for shipping other potted plants. Retail outlets that display plants
out-of-doors must also be aware that caladiums will not tolerate the








low night temperatures and windy conditions that occasionally oc-
cur in late spring. And, of course, consumers should be warned to
plant caladiums only when night temperatures are 55 OF or higher.

Propagation by Tissue Culture or Seeds
Two different propagation techniques that show promise for pot-
ted plant production are the use of tissue-cultured and seed-
propagated caladium plants. Explants or seedlings with three to four
leaves (about the size of the popular "plugs" that are marketed for
other potted plants now) will reach marketable size in 4-inch pots
about six weeks from transplanting. The advantage to this techni-
que is that many small leaves are formed on each plant (20 or more
in six weeks with Frieda Hemple, for example), which gives the
plants the ideal pot-to-shoot ratio. When growing tissue-cultured
plants, the fertilization should be increased to 12 lbs/yd3 of Osmocote
14-14-14, or a 500 ppm N-P-K solution should be applied twice a
week.

Pest Problems
Occasionally, root aphids or mealy bugs proliferate on tubers dur-
ing storage. If insects are detected on tubers, an appropriate insec-
ticidal dip prior to planting will control the problem. Mites, aphids,
mealy bugs and lepidopterous larvae (caterpillars) may attack foliage
of plants forced from tubers or tissue-cultured explants. Since the
turnover of caladiums is rapid, a scouting procedure and applica-
tion of insecticides on demand appears to be a better approach than
preventive sprays.
Tubers should be surveyed for rots caused by fungal organisms or
bacteria. Healthy tubers are firm (see Cold Injury) and the fleshy
part of the tuber is bright yellow. Internal discoloration, such as
brown streaks or milky-white areas with a pungent odor, is an in-
dication of infection. Severely infected tubers should be discarded.
Tissue-cultured plants appear to be susceptible to root rots im-
mediately after transplanting. Preventive drenches of broad spec-
trum fungicides, especially those controlling pythium, should be
considered.
Caladiums can be as easy, predictable, fast, and profitable to pro-
duce as most other potted plants when these guidelines are follow-
ed. This crop provides growers with a unique type of plant for spring
or early summer sales. Additionally, with improved tuber storage
techniques or with the use of tissue-cultured plants, potted caladiums
may be used the year around in both the traditional florist trade and
as added color for the foliage plant industry.








low night temperatures and windy conditions that occasionally oc-
cur in late spring. And, of course, consumers should be warned to
plant caladiums only when night temperatures are 55 OF or higher.

Propagation by Tissue Culture or Seeds
Two different propagation techniques that show promise for pot-
ted plant production are the use of tissue-cultured and seed-
propagated caladium plants. Explants or seedlings with three to four
leaves (about the size of the popular "plugs" that are marketed for
other potted plants now) will reach marketable size in 4-inch pots
about six weeks from transplanting. The advantage to this techni-
que is that many small leaves are formed on each plant (20 or more
in six weeks with Frieda Hemple, for example), which gives the
plants the ideal pot-to-shoot ratio. When growing tissue-cultured
plants, the fertilization should be increased to 12 lbs/yd3 of Osmocote
14-14-14, or a 500 ppm N-P-K solution should be applied twice a
week.

Pest Problems
Occasionally, root aphids or mealy bugs proliferate on tubers dur-
ing storage. If insects are detected on tubers, an appropriate insec-
ticidal dip prior to planting will control the problem. Mites, aphids,
mealy bugs and lepidopterous larvae (caterpillars) may attack foliage
of plants forced from tubers or tissue-cultured explants. Since the
turnover of caladiums is rapid, a scouting procedure and applica-
tion of insecticides on demand appears to be a better approach than
preventive sprays.
Tubers should be surveyed for rots caused by fungal organisms or
bacteria. Healthy tubers are firm (see Cold Injury) and the fleshy
part of the tuber is bright yellow. Internal discoloration, such as
brown streaks or milky-white areas with a pungent odor, is an in-
dication of infection. Severely infected tubers should be discarded.
Tissue-cultured plants appear to be susceptible to root rots im-
mediately after transplanting. Preventive drenches of broad spec-
trum fungicides, especially those controlling pythium, should be
considered.
Caladiums can be as easy, predictable, fast, and profitable to pro-
duce as most other potted plants when these guidelines are follow-
ed. This crop provides growers with a unique type of plant for spring
or early summer sales. Additionally, with improved tuber storage
techniques or with the use of tissue-cultured plants, potted caladiums
may be used the year around in both the traditional florist trade and
as added color for the foliage plant industry.








Related Literature


Black, R. J. and B. Tjia. 1979. Caladiums for Florida. Circ. 469,
Florida Cooperative Extension Service, University of Florida,
Gainesville, FL.
Conover, C. A. and R. T. Poole. 1973. Influence of shade level and
soil temperature on forcing of caladium bicolor. Proc. Fla. State
Hort. Soc. 86:369-372.
Conover, C. A. and R. T. Poole. 1975. Influence of fertilizer level,
apical bud removal, and tuber orientation on forcing of caladium
bicolor. HortScience 10:226-227.
Harbaugh, B. K., F. J. Marousky, and J. A. Otte. 1979. Warm
temperature the key to forcing caladiums. Florists' Rev.
163:64-68.
Harbaugh, B. K., F. J. Marousky, J. F. Price, and D. J. Schuster. 1979.
Guidelines for forcing caladiums. Florida Ornamental Growers'
Assn. Newsletter 2:4-5.
Harbaugh, B. K., J. W. Prevatt, and J. A. Otte. 1980. Irrigation
systems for pot-plant production in Florida Economic and hor-
ticultural implications. Bradenton AREC Res. Rept. GC1980-1.
Harbaugh, B. K., and G. J. Wilfret. 1982. Correct temperature is the
key to successful use of Osmocote. Florists' Rev. 170:20, 23.
Harbaugh, B. K. 1982. Caladiums as bedding plants. Proc. 15th An-
nual Conf. of Bedding Plants, Incorporated. 1982:279-283.
Harbaugh, B. K. and A. J. Overman. 1983. Evaluation of fertilizer
types and rates on Caladium hortulanum Birdsey 'Candidum'
tuber production in muck and sandy soil management systems.
Proc. Fla. State Hort. Soc. 96:250-254.
Hartman, R. D. 1974. Dasheen mosaic virus and other
phytopathogens eliminated from caladium, taro, and cocoyam by
culture of shoot tips. Phytopathology 64:237-240.
Hartman, R. D. 1983. New Plant for All Seasons. Florida Foliage
9(12):9-11.
Knauss, J. 1975. Description and control of Fusarium tuber rot of
caladium. Plant Dis. Reptr. 59:975-979.
Marousky, F. J., and J. C. Raulston. 1973. Influence of temperature
and duration of curing, storage, shipping and forcing periods on
caladium growth. Proc. Fla. State Hort. Soc. 86:363-368.
Marousky, F. J. 1974. Influence of curing and low temperatures dur-
ing storage on subsequent sprouting of caladium tubers. Proc. Fla.
State Hort. Soc. 87:426-428.
Marousky, F. J. and B. K. Harbaugh. 1976. Influence of relative
humidity on curing and growth of caladium tubers. Proc. Fla. State
Hort. Soc. 89:284-287.








Muzzell, A. E., Jr., and J. N. Joiner. 1966. Effects of methods of
cut, heat treatment and planting placement on forcing caladium
spp. Candidum. Proc. Fla. State Hort. Soc. 79:446-451.
Overman, A. J. and B. K. Harbaugh. 1982. Effect of tuber source
and fumigation on caladium tuber production in two soil manage-
ment systems. Proc. Fla. State Hort. Soc. 95:175-178.
Overman, A. J. and B. K. Harbaugh. 1983. Soil fumigation increases
caladium tuber production on sandy soil. Proc. Fla. State Hort.
Soc. 96:248-250.
Poole, R. T. and C. A. Conover. 1972. Factors influencing forcing
of caladiums. Apopka ARC Res. Rept. RH73-3.
Poole, R. T. and C. A. Conover. 1977. Sprouting of caladiums as in-
fluenced by planting date. The Florida Nurseryman (Sept.
1977):25.
Rhoades, H. L. 1964. Effect of hot water treatment of seed tubers
and soil fumigation for control of root knot on yield of caladiums.
Plant Dis. Reptr. 48:568-571.
Ridings, W. H. and R. D. Hartman. 1976. Pathogenicity of Pythium
myriotylum and other species of pythium to caladium derived
from shoot-tip culture. Phytopathology 66:704-709.
Sheehan, T. J. 1960. Caladium Production in Florida. Univ. of Fla.
Agr. Ext. Ser. Circ. 128. Gainesville, FL.
Wilfret, G. J. 1981. Caladiums for Florida gardens. Florida Garden
Guide, March/April, 1982.
Wilfret, G. J. and G. T. Hurner, Jr. 1982. A survey of caladium
cultivars grown in Florida and their characteristics as potted
plants. Proc. Fla. State Hort. Soc. 95:190-194.
Wilfret, G. J. 1983. Tuber production of caladium cultivars grown
in a sandy soil. Proc. Fla. State Hort. Soc. 96:245-248.
Zettler, F. W., J. J. Foxe, R. D. Hartman, J. D. Edwardson, and R.
G. Christie. 1970. Filiamentous viruses infesting dasheen and other
araceous plants. Phytopathology 60:983-987.
Zettler, F. W. and M. M. Abo El-Nil. 1979. Mode of inheritance of
foliage color in caladium. J. Heredity 70:433-435.
Zettler, F. W., M. M. Abo El-Nil, and R. D. Hartman. 1981. In-
heritance of caladium foliage color patterns. Fla. Orn. Growers
Newsletter 6:2-3.






















































This publication was promulgated at a cost of $448, or 16 cents
per copy, to inform commercial ornamental growers on how to
force caladiums. 8-2.8M-85.


COOPERATIVE EXTENSION SERVICE, UNIVERSITY OF FLORI-
DA, INSTITUTE OF FOOD AND AGRICULTURAL SCIENCES, K. R.
Tefertlller, director, In cooperation with the United States Department A
of Agriculture, publishes this information to further the purpose of the
May 8 and June 30, 1914 Acts of Congress; and is authorized to pro-
vide research, educational Information and other services only to Indl-
viduals and Institutions that function without regard to race, color, sex or national ori-
gin. Single copies of Extension publications (excluding 4-H and Youth publications) are
available free to Florida residents from County Extension Offices. Information on bulk
rates or copies for out-of-state purchasers Is available from C. M. HInton, Publications
Distribution Center, IFAS Building 664, University of Florida, Galnesvllle, Florida
32611. Before publicizing this publication, editors should contact this address to deter-
mine availability.