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Bradenton GCREC Research Report BRA1993-29
Institute of Food and Agricultural Sciences December 1993
Effect of Shade Level on Caladium Tuber Production Lik ry
MAY 2 0 19
Brent K. Harbaugh1
University of Florida
Caladium tubers are produced in field culture without use of any structures.
While this practice has been used in the caladium industry for many years, the
foliage of most caladium cultivars exhibits high light and/or temperature stress
symptoms when grown under full sun. Cultivars are often classified by their
shade or sun requirements. However, this classification was developed to
indicate the influence of light intensity on leaf color and size for potted or
landscape plants. Information is lacking for the effect of light levels on
production of tubers. This research was conducted to determine if shade
structures could be used to increase caladium tuber production compared to tuber
production under full sun.
Materials and Methods
Three light levels were evaluated (full sun, 30% shade and 47% shade) for their
effect on caladium tuber production. Temporary structures were constructed over
field plots and were left uncovered or covered with 30 or 47% polypropylene shade
cloth. Structures were 24 ft. long, 15 ft. wide, 6 ft. high and were constructed
similar to shade-houses used by the commercial cut flower industry. The
experimental design was a randomized complete block with three replications of
15 plant plots.
One inch diameter seed pieces of 'Carolyn Whorton', 'Frieda Hemple', and 'Red
Frill' caladiums were planted on May 19th in ground beds of EauGallie fine sand.
Spacing was 5 inches within and between rows, with 3 rows across and 5 rows down
the plot. Cultivars were separated by an 18 inch unplanted border. Osmocote
18-6-12 controlled release fertilizer (8 to 9 month release at 70F) was applied
at 300 Ibs N/planted acre. Plants were supplied water with seep irrigation.
Tubers were harvested on Dec. 9th, cured for one week, and then weighed and
graded into commercial sizes. Commercial sizes were: No. 3 = < 1 inch; No. 2
= 1 to 1.5 inches; No. 1 = 1.5 to 2.5 inches; Jumbo = 2.5 to 3.5 inches; Mammoth
= 3.5 to 4.5 inches in diameter. A production index was used to reflect crop
value as prices change from year to year or grower to grower, but the differences
in prices between grades usually remain constant: Production index = No. 3 +
1.5(No. 2) + 3(No. 1) + 6(Jumbo) + 9(Mammoth).
'Professor of Environmental Horticulture.
Tuber weights of 'Frieda Hemple' and 'Red Frill' were greater from plants grown
under 30% shade compared to tubers produced under full sun. Tubers of 'Carolyn
Whorton' and 'Red Frill' weighed more when produced with 47% shade rather than
under full sun. 'Frieda Hemple' tubers produced under 47% shade were
intermediate in weight between those produced with full sun and 30 % shade. 'Red
Frill' tubers produced under 47% shade were similar in weight to those produced
at 30% shade.
Shade level influenced the number of tubers in certain grades for all cultivars.
For 'Carolyn Whorton' and 'Frieda Hemple', more mammoths were produced with 30%
shade than with full sun. 'Red Frill' plants did not produce any mammoth sized
tubers with any light level, which is typical for a lance-leaf cultivar.
However, there were more Jumbo tubers produced under 30% shade compared with full
sun. In general for all cultivars, there were greater numbers of tubers in one
of the lower grades (No. 3, No. 2 or No. 1) with full sun compared to tuber
grades for shaded plants, and greater numbers of a tubers in higher grades (Jumbo
or mammoth) with shaded plants.
The production index was greater for 'Frieda Hemple' and 'Red Frill' tubers grown
with 30% shade compared to full sun. With 'Red Frill', the production index was
also greater for tubers from 47% shade. 'Frieda Hemple' tubers produced with 47%
shade had an intermediate value between that of tubers produced with full sun or
30% shade. There were no differences in the production index for 'Carolyn
Structures providing 30% shade increased the value of tubers 24% for 'Frieda
Hemple' and 57% for 'Red Frill'. While these are very significant increases for
these two cultivars, it should be noted that no significant increases were found
for tuber value due to shade for 'Carolyn Whorton'. Thus, other cultivars should
be evaluated before consideration of production under shade. In addition,
caution needs to be exercised in extending these results beyond the one year
scope of this preliminary study. Further studies are necessary since
environmental conditions change so dramatically from year to year, especially
during a crop that takes at least 6 months to produce. These yearly changes
would necessitate studies over a period of years before a consistent benefit from
production of caladiums with shade structures could be established. However,
these preliminary results indicate that further investigation is warranted.
Table 1. Effect of 0, 33, or 47% shade on tuber production of caladium 'Carolyn
Whorton', 'Frieda Hemple' and 'Red Frill'.
Number of tubers by grade Productionz
% Shade Weight (q) Three Two One Jumbo Mammoth index
0 1353 by 2 1 8 a 7 1 b 76
30 1767 ab 2 1 5 ab 6 3 a 85
47 1987 a 1 ns 1 ns 3 b 8 ns 3 ab 89 ns
0 1353 b 0 3 7 7 2 b 89 b
30 2026 a 0 1 6 7 5 a 110 a
47 1676 ab 0 ns 0 ns 5 ns 9 ns 3 b 94 ab
0 283 b 5 a 7 4 b 0 b 0 30 b
30 563 a 3 b 5 8 ab 2 a 0 47 a
47 626 a 1 b 5 ns 10 a 1 ab 0 ns 46 a
ZProduction index = No. 3 +
YMean separation in columns
1.5(No. 2) + 3(No. 1) + 6(Jumbo) + 9(Mammoth).
for each cultivar by LSD, Alpha = 0.1. NS = not