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Plant Propagation via Leaf Cuttings in Four Aquatic Species: Bur-Mangold,
Sky Flower, East Indian Hygrophila and Water Primrose
Susan Peters
ABSTRACT
Economical methods for propagation of aquatic plants would help nursery growers in Florida effectively meet the
need for ornamental landscaping and wetland restoration. Propagation of aquatic plants by leaf cuttings, as
is commonly done with begonia (Begonia spp.) and African violet (Saintpaulia spp.) plants, would provide
growers with a simple, inexpensive means of producing and promoting new species for the aquatic plant industry.
To provide information on propagation by leaf cuttings, root and shoot initiation in four uniquely different
aquatic species was evaluated under greenhouse conditions at the University of Florida Research and
Education Center in Fort Lauderdale, Florida, from 15 May 2000 through 28 September 2000. Bur-marigold
(Bidens laevis (L.) BSP), a perennial wetland native of Florida, was selected for the study due to its potential use
in mass plantings and erosion control. Sky flower (Hydrolea corymbosa Macbr. ex Ell.), an aquatic
perennial, produces a multitude of cornflower-blue blossoms throughout the summer months and shows promise
in aquatic landscape settings. The third plant evaluated, East Indian Hygrophila (Hygrophila polysperma (Roxb.)
T. Anderson), is listed as a weedy, invasive species by the USDA and was included due to its phenomenal capacity
to produce abundant new plants from leaf cuttings. Lastly, water primrose (Ludwigia peruviana (L.) Hara), a
common native plant with attractive yellow flowers, was studied since it is profuse and well adapted to this area.
INTRODUCTION
As the Florida population continues to grow, more and more wetland areas are lost to expansion and
urbanization. Fortunately, public awareness has increased in the past few years and this has created the need
for aquatic plant nurseries in Florida, which play a vital role in supplying ornamental aquatic plants for
homeowners and native plants for use in wetland restoration projects. Development of efficient methods
for propagation of aquatic plants will be of great benefit to the nursery industry by helping lower their
production costs. Only a limited number of plant species can be produced via leaf cuttings (Hartman et al., 1997)
and only a few aquatic plants produce new plants (i.e., adventitious roots and shoots) from their leaves. Little
is known of the factors that cause plants to reproduce in this manner. If high numbers of plants could be
produced from leaf tissue, this would eliminate the need to use costly tissue culture methods now employed for
some aquatic species. Our study utilized whole leaves and top and bottom halves of leaves to evaluate
adventitious root and shoot formation in four uniquely different species of aquatic plants: Bur-marigold (Bidens
laevis (L.) BSP); sky flower (Hydrolea corymbosa Macbr. ex Ell.); East Indian Hygrophila (Hygrophila
polysperma (Roxb.) T. Anderson); and water primrose (Ludwigia peruviana (L.) Hara).
Bur-marigold, a member of the Asteraceae family, occurs throughout Florida in wetland habitats such as
meadows, marshes, ditches, slow-moving streams, and banks. Bur-marigold is an annual but functions as a
short-lived perennial in our area of south Florida. Generally no more than 1.0 m in height, bur-marigold assumes
a decumbent growth habit; the species reclines on the ground and roots at the nodes, often forming mats up to
2.0 m across. Leaves are opposite, lanceolate to elliptical in shape, unlobed, and sessile. Flowers which occur in
late summer to early fall, are typical of the aster family and are large with bright yellow ray and disk flowers
(Figure 1). Resulting achenes (seeds) are numerous, strongly flattened and bear the classic two awns
(narrow bristle-like appendages on each side) which aid in seed dispersal and give rise to the common names used
to describe this species, including beggar-ticks, stick tights and bur-marigolds. Bur-marigold spreads readily by
seed and is potentially useful in mass plantings and for erosion control. This species has been recommended for
use in wetland restoration projects as a shallow water plant in areas with water levels to 30 cm in depth (Godfrey
I IN I JOUI-11,11 of U'ridergradWItC Rc.,carch University of Florida
and Wooten, 1981; Loftin, 1994; Tobe et al., 1998).
1 3.
AwOSS
Figure 1. Flower and leaf cutting of bur-marigold
Sky flower is a member of the Hydrophyllaceae or Waterleaf family. Hydrolea corymbosa (the particular
species used in this experiment) is the most common of the sky flowers seen in Florida and ranges from Leon
County east and all the way south to Monroe County. It is a perennial herb, growing in and around shallow water
in swampy woodlands, marshes, and ditches. The plant is 0.60 to 0.80 m in height with smooth or pubescent
stems, and alternate, elliptic to lanceolate shaped leaves. Every summer, and extending into the early fall
months, sky flower offers a profusion of flat or round-topped inflorescences called cymes with an intense shade
of cornflower blue, although the blossoms may be purple or even white (Figure 2). Individual flowers are
bisexual with five petals each. Seed pods contain numerous, extremely small, oval-shaped seeds that
germinate readily, although new plants are produced from rhizomes as well. Sky flower has been successfully
grown in standard 2-gallon containers for several years at the Fort Lauderdale Research and Education Center.
Sky flower has not yet been used as an aquatic landscape ornamental; however, its beauty and growth habit
suggest significant potential (Gettys and Sutton, 1999; Godfrey and Wooten, 1981; Sutton and Robinette, 1996).
Figure 2a. Flower and growth habit of sky flower
Figure 2b. Close-up of sky flower
East Indian Hygrophila, first introduced into Florida in the 1950s for use in the aquatic ornamental industry,
is native to the East Indies and a member of the Acanthaceae family. East Indian Hygrophila, also known as
"Miramar Weed" (Vandiver, 1980) began creating serious weed problems in South Florida waterways in
1980, invading many of the habitats formerly populated by Hydrilla verticillata (L. f.) (Sutton, 1995). It is
now naturalized in many rivers, canals, and static bodies of water in numerous Florida counties and is considered
a noxious, weedy species by the United States Department of Agriculture (USDA, 2000). Weed problems
currently occur primarily in warm areas of the state; however, the plants may withstand cold water temperatures
as well (Schmitz and Nail, 1984). Generally, East Indian Hygrophila prefers riverine habitats, growing profusely as
a rooted, submersed, herbaceous perennial with square, decumbent stems and short stalks. Leaves are lanceolate
or lance-elliptic, opposite and 2.0 to 7.0 cm in length. East Indian Hygrophila produces small, bisexual flowers
(bluish-white in color) in apical leaf axils in the winter months (Figure 3). The resultant seeds dehisce from
capsules and may, or may not, play a major role in reproduction, as asexual reproduction readily occurs
from portions of the brittle stems that break away from the parent plants. Large floating mats of vegetation
clog Florida waterways, effectively disseminating East Indian Hygrophila to new habitats where stems easily
create new plants by forming adventitious roots at the nodes.
Figure 3. Flower and growth habit of hygrophila
Water primrose, also known as seed box, is a wetland member of the Onagraceae or Evening Primrose
Family. Water primrose is considered a native species and is found abundantly in Central Pensacola and South
Florida in shallow water habitats such as ditches, marshes, swamps, and the like. It grows to a height
of approximately 1.8 m as an annual or, more often, as a well-branched perennial herb or subshrub (due to
the woodiness that develops at the base). Leaves, especially when young, are pubescent, alternate, and lanceolate
in shape with tiny glandular stipules. Large, showy yellow flowers with 4 or 5 petals each are produced in the
summer and fall months in the upper leaf axils (Figure 4). The resulting seed capsules are approximately 2.5 cm
in length, broadly obconic and quadrangular at the apex. Water primrose seeds are eaten by ducks and
other waterfowl which, no doubt, explains the number of "volunteers" occurring profusely in the South
Florida landscape. Many Ludwigias are so abundant they are considered a "nuisance native" (Burks,
personal communication), although others appreciate its decorative flowers and potential use in
"emerse cultivation" (Muhlberg, 1980).
Figure 4a. Flower of water primrose
Figure 4b. Growth habit of water primrose
MATERIALS AND METHODS
Commercially available materials that are commonly used by the nursery industry were used in this
study. Propagation trays with drainage (52.0 x 26.0 x 6.0 cm) were lined with paper toweling and filled to a level
of approximately 1.0 cm with Scotts Metro-Mix 500� potting medium. Filled trays were sprayed with water to
fully hydrate the potting medium and then allowed to drain. The plant material, consisting of fresh leaves from
the four above-described species, was harvested from well-nourished stock plants and immersed in fresh
water pending placement on the propagation trays. Each tray consisted of 12 leaves of one species placed flat on
the surface of the moistened medium &endash; apex pointed to the top of the tray and base (petiole) pointed to
the bottom of the tray (Figure 1). Each propagation tray held 12 leaves as follows: six whole leaves (WL), six
leaves horizontally cut in half resulting in six sections designated as the "top of leaf" (TOL) and six
sections designated as the "bottom of leaf" (BOL). Once prepared, all trays were placed under mist (10
second duration at 15 minute intervals, 24 hours per day, 7 days per week) in a teaching greenhouse.
Four independent replicates of this experiment were conducted between 15 May and 28 September
2000. Temperatures were recorded on the mist bench of the greenhouse (Table 1).
Table 1
Greenhouse Temperatures
Culture Min. Max.
CuuPeriod Dates Temp. Temp.
(OC) (OC)
15
1 May 190 345
to 12
Jun 00
25
2 May 205 370
to 22
Jun 00
15
Aug
3 to 12 205 370
Mean Temp. (OC)
RESULTS
Our results follow in Table 2, below. Values for root and shoot production are listed as percentages for whole
leaves (WL), top of leaves (TOL), and bottom of leaves (BOL) placed under mist in a greenhouse for 4 weeks.
Each value is based on a mean of 6 leaves or cuttings.
Table 2
Root and Shoot Production in Leaf Cuttings after 4 Weeks
Production
Plant/ Roots Shoots
Culture
Period WL TOL BOL WL TOL BOL
Bur-marigold
1 50 0 17 0 0 0
2 33 0 33 0 0 0
3 50 0 0 0 0 0
4 83 17 50 0 0 0
Sky Flower
1 33 0 67 17 0
2 33 0 50 0 0
3 67 33 33 0 0
4 83 17 83 17 0
E Indian Hygrophila
1 100 100 100 100 100
2 100 100 100 100 100
3 100 100 100 100 100
4 100 100 100 100 100
Water Primrose
1 0 0 0 0 0
2 0 0 0 0 0
3 0 0 0 0 0
0
0
0
0
DISCUSSION
The lack of adventitious root and shoot production in bur-marigold and water primrose suggests that it is not
possible to propagate these two species using leaf cuttings. East Indian Hygrophila was propagated efficiently
and readily and produced adventitious roots and shoots in 100% of the leaf cuttings by week 4 (Figures 5 and
6). Unfortunately, it remains listed by the U.S. Government as a noxious, weedy species and cannot be offered
for commercial use in the state of Florida. Interestingly enough, East Indian Hygrophila is commercially raised
by Florida aquatic nurserymen and marketed out-of-state for the aquarium trade. Of all the locally
marketable species evaluated, sky flower exhibited the most promise. Our findings suggest that, given time,
sky flower will produce both adventitious roots and shoots from leaf cuttings. Additional studies should be
undertaken to more fully evaluate its potential for propagation by leaf cuttings and use in aquascape and
restoration projects.
I f cle. - , i i Top llft |W B=atdnol..�
Root production (%)
Shoot production (%)
Figure 5. Production of roots and shoots by East Indian Hydrophila from 15 MAy to 12 June 2000
held under mist in a greenhouse. Each value is the mean of six leaf cuttings.
- 1d.I6.1 = T.pMoff =lZ
31
Aug
4 to 28 220 360
Figure 6. Production of roots and shoots by East Indian Hygrophila from 31 Aug to 28 Sept 2000
held under mist in a greenhouse. Each value is the mean of six leaf cuttings.
ACKNOWLEDGEMENTS
We thank Lyn Gettys for her "focus" and expertise in solving the mysteries of the SigmaPlot software, and
Joanne Korvick for good-natured moral support and assistance in the greenhouse.
0 0 17 0 0
REFERENCES
Burks, Kathy. E-mail exchange of information from Ms. Burks at the Bureau of Invasive Plant Management, State
of Florida. 28 November 2000.
"Federal Noxious Weed List." United States Department of Agriculture. Online 2000. Internet. Available http://
www.aphis.usda.gov/ppq/weeds/noxwdsa.html.
Gettys, Lyn A. and David L. Sutton. "Sky flower." Aquatics 21.4 (1999): 4-9.
Godfrey, Robert K. and Jean W. Wooten. Aquatic and Wetland Plants of Southeastern United States. Georgia:
The University of Georgia Press, 1981.
Hartmann, Hudson T., Dale E. Kester, Fred T. Davies and Robert L. Geneve. Plant Propagation: Principles
and Practices. New Jersey: Prentice Hall, 1997.
Loftin, Jan P. "On the Waterfront." Florida Water, Summer 1994.
Muhlberg, Helmut. The Complete Guide to Water Plants. German Democratic Republic: EP Publishing Limited, 1982.
Schmitz, Don C. and Larry E. Nail. "Status of Hygrophila polysperma in Florida." Aquatics 6.3 (1984): 11-14.
Sutton, David L. "Hygrophila is Replacing Hydrilla in South Florida." Aquatics 17.3 (1995): 4-10.
Sutton, David L. and D. Lamar Robinette. 1996. "Use of Native Aquatic Plants as Backyard Ornamentals." Proc.
Fla. State Hort. Soc. 109:301-303.
Tobe, John D., Kathy Craddock Burks, Richard W. Cantrell, Mark A. Garland, Maynard E. Sweeley, David W. Hall,
Pete Wallace, Guy Anglin, Gil Nelson, James R. Cooper, David Bickner, Katherine Gilbert, Neil Aymond,
Ken Greenwood and Nina Raymond. Florida Wetland Plants: An Identification Manual. Tallahasee: Florida
Department of Environmental Protection, 1998.
Vandiver, Vernon V. "Hygrophila." Aquatics 2.4 (1980): 4-11.
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