Tropi cLinevolume 6, Number 5, September-October, 1993
Editor: Alan W. Meerow
Christine T. Stephens, Dean, Cooperative Extension
A Method for
Germination of Arrowhead,
Pickerelweed, and Spikerush
David L. Sutton
Aquatic Plant Researcher
Native aquatic plants are in high demand for restoration and mitigation
projects. Information is needed on commercial production of native aquatic
plants because of recent changes by the Florida Department of Environmental
Regulation that limit collection of native plants for use in these
Many aquatic plants produce an abundance of seeds, but little information
is available on their germination for use in commercial nursery operations.
For the past several years we have been investigating potential methods for
germination of emersed aquatic plant seeds for use in the production of
seedlings for use in lake restoration and wetland mitigation projects.
Previously, we found seeds to germinate better in muck soil than in sand
during germination studies with several emersed aquatic plants, but
sprouting of a number of unwanted weed seeds also occurred in the muck
soil. These germination studies also showed that the addition of fertilizer
to the muck soil was necessary for good growth of the seedling aquatic
plants. This study was conducted with a sterilized potting medium in an
attempt to eliminate sprouting of unwanted weed seedlings.
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Seeds of arrowhead (Sagittaria lancifolia L. and Sagittaria latifolia
Willd.), pickerelweed (Pontederia cordata var. lancifolia (Muhl.) Torrey),
and spikerush (Eleocharis cellulosa Torr.) were collected from mature
plants in culture at the Fort Lauderdale REC.
The seeds were stored in an air-conditioned room until needed for use in
germination tests. Germination tests were conducted by sowing 25 seeds in
standard 1-gallon nursery plastic pots (Fig. 1, Fig. 2). For each
germination test, 10 pots were used for a total of 250 seeds.
An ice pick was used to punch holes in the pots which allowed water to
enter and saturate the sand and soil (Hyponex potting soil). The pots were
placed in such a manner that the top of the soil was approximately 1 inch
above the water surface in an outdoor cement tank located at the FLREC. The
dimensions of the tank were 20 feet in length by 10 feet in width with pond
water at a depth of 14 inches. Pond water flowed into the tank on the
surface at one end and out of the tank from a bottom drain at the other at
a rate which allowed for a complete exchange of water every 24 hr.
Media used in the pots were coarse builders' sand and Hyponex potting soil.
Prior to placing the Hyponex potting soil in the pot, it was autoclaved for
1 hour at 250 Fo with 15 pounds of pressure. Then the soil was dried at 140
Fo for 7 days, and allowed to cool prior to placing it in the pots.
The fertilizer layer in each pot was equivalent to 2.3 oz of 18-6-12
Osmocote formulated for an 8- to 9-month release rate at 70 Fo per ft2,
0.08 oz of dolomite per ft2, and 0.08 oz of Esmigran per ft2.
Seeds of S. lancifolia were sown on July 3, 1989 and allowed to germinate
for 6 weeks. Two batches of S. latifolia seeds collected from different
donor plants were sown on February 23, 1990 and allowed to germinate for 6
weeks. Pickerelweed and spikerush seeds were sown December 12, 1989, and
allowed to germinate for 12 weeks. The pots were observed weekly, and the
number of sprouted seeds counted.
RESULTS AND DISCUSSION
Seeds of S. latifolia arrowhead seeds began sprouting within 2 weeks of
being placed in the pots and approximately 70% of them had germinated
within 6 weeks.
Germination of S. lancifolia seeds was not observed until 4 weeks after
they had been sown in the pots (Fig. 3). After 6 weeks only 29% of these
seeds had germinated.
Pickerelweed seeds began sprouting within 3 weeks after being sown in the
pots, and by the end of 12 weeks almost 25% of them had germinated (Fig.
Seedlings of spikerush did not appear until 7 weeks after they had been
sown in the pots, and only 1- of the seeds had germinated by the end of
the 14 weeks (Fig. 5). Extending the germination period for E. cellulosa
seeds beyond 14 weeks would probably not improve germination. When the
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plants were removed from the pots after the 14-week period, several of the
seedlings appeared to have formed from rhizomes and a number of the
seedlings were beginning to form rhizomes with buds which would quickly
result in an increase in the number of new plants.
Although the aquatic plant seeds tested in this study were not sown on
different dates, S. latifolia seeds displayed the highest germination rate
under these conditions. The spikerush, E. cellulosa, seeds exhibited the
lowest rate of these emersed plant species studied.
The use of sterilized soil was intended to eliminate the germination of
unwanted seeds in the soil used in this study. However, under the outdoor
conditions of the study, seedlings of the spikerush Eleocharis geniculata
(L.) R. & S. were found in some of the germination containers on several
occasions. The germination containers attracted various birds. Perhaps the
spikerush seeds were carried on the feet of these birds, or the seeds many
have been wind born. In commercial nursery operations, precautions will
need to be taken to prevent the introduction of unwanted weed seeds by
birds, wind, or other means. This study shows the potential of using
sterilized soil to essentially eliminate problems with unwanted weed seeds
in the production of aquatic plant seedlings. Poor germination of some of
the seeds in this study may have been the result of birds eating the seeds,
lack of sufficiently mature seeds, or other problems related to
environmental factors such as temperature.
Aquatic plant images provided by the Information Office of the University of Florida, IFAS, Center for
Aquatic Plants (Gainesville)
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