Nursery Production of Uniola paniculata
(southern seaoats)
Gary R. Bachman and Ted
Whitwell
Department of Horticulture, Clemson University
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Introduction
Uniola paniculata (southern seaoats) is the dominant foredune
building grass from southeastern Virginia along the Atlantic and Gulf coasts
to eastern Mexico. This perennial grass has been used extensively to build
artificial dunes and stabilize existing dunes. With the increased shoreline
damage by tropical storms on the eastern seaboard in the last few years,
the need for beach restoration also has increased. Vegetative porpagation
for dune restoration in beach sand is expensive, and young plants are subjected
to extreme environmental factors which can result in poor plant establishment
and growth. Direct seeding in the dunes is ineffective because of seed
dormancy-viability and movement of sand which affects planting depth.
Unlike many grasses, seaoats is not a prolific seed producer. Therefore,
the primary natural method of reproduction in the dune habitat is through
vegetative means. Buds are formed around the stem base, and the formation
angle of the buds determine whether a shoot or lignified rhizome develops.
Acutely angled buds become tillers and right angled buds become rhizomes.
Internodal potions of the rhizomes decay leaving the nodal regions with
associated culms to root and become new plants. As sand is deposited around
the base of the plant, these rhizomes establish roots in dune sand.
The dune habitat found along the coastal regions of the Southeast lacks
sufficient nutrients for optimal growth. Commercial nurseries in the Southeast
commonly use pine bark-sand media, which is also nutrient-deficient. Nurseries
attempt to maintain adequate nutrition by using quick-release granular fertilizer,
controlled-release fertilizer or fertilizer injected into irrigation water,
alone or in combinations. Macronutirent fertilizers commonly are applied
to stimulate plant growth and increase vegetative cover in dune plantings.
Production of seeded Uniola paniculata in commercial nurseries would
increase availability of plants for dune restoration. The objectives of
this research were to 1) enhance germination of freshly harvested seed,
2) investigate the effect of planting depth within containers to simulate
the dune enviroment, where the base of the plant is buried, and 3) determine
an optimum nutrition program for Uniola paniculata grown in pine
bark-sand media for nursery production.
Materials and Methods
Seed germination . Mature Uniola paniculata panicles
were harvested from the Jekyll Island, Ga. area 15 Sept. 1993 in cooperation
with the Jekyll Island Authority. The spikelets were rubbed over a screen
to remove the chafe, and the seeds were collected. Harvested seeds were
stored dry at 40°F for 30 days. Before treatments, all seeds were soaked
for 30 min in a 30% bleach solution as a surface sterilant. Seed treatments
included 24h soak in 100 or 500 ppm gibberillic acid (GA4) or
distilled water. Scarificaton also was applied to the seeds across all GA4
treatments. Seeds were scarified using 600-grit sandpaper and gently rubbing
the seeds between fingers. A scarified only and
non-treated control were included.
Seeds were planted in 40-cell trays using a standard nursery seed propagation
media of 1:peat moss: 1 perlite (by volume) and germinated in a shadehouse
at Carolina Nurseries, Moncks Corner, S.C. Preplant fertilization for all
treatments included incorporation of 9 lb/yd3 18N-2.6P-9.9K Osmocote and
9 lb/yd3 14-7-7 granular fertilizer. A preplant drench of Banrot at
8 lb/100 gal was applied. Seed were planted 1 inch deep with two seeds per
cell.
The 40-cell trays were irrigated by mist for 5 min initially followed by
mist every 16 min for 8 sec during the first 10 days and then every 32 min
for 8 sec for the remainder of the study. The study was started on 17 Nov.
1993 and concluded 20 Dec. 1993. On 20 Dec. 1993, germination percentages
were determined for the seed treatments.
A follow-up study was conducted in a glass greenhouse at Clemson University.
Seeds collected at Jekyll Island and stored at 4°C for 136 days were
planted in a peat-based medium, Fafard 3B. Two planting depths were studied,
0.5 and 1 inch. Seeds were given preplant treatments consisting of a control
and 24-h soaks in distilled water, 100 ppm gibberillic acid (GA4),
and 7 mM and 14 mM thiourea. There were four replications of of each seed
treatment x planting depth combination with five cells per replicate. On
8 Feb. 1994, before planting, all seeds were disinfected by immersing in
30% bleach solution for 30 min and the medium was drenched with Banrot at
8 lb/100 gal. The seeds were planted in a 200 cell plug tray with two seeds
per cell with mist. Bottom heat was provided at a constant temperature of
25°C. The study was begun 9 Feb. 1994 and terminated 9 Mar. 1994.
Planting depth . Well rooted seed-grown liners of Uniola
particulata were planted in a 4 pine bark: 1 sand (by volume) media
on 15 Mar. 1994 at Carolina Nurseries into full 1-gal and 3-gal tree containers.
The liners were placed in the containers with the crown either even with
the surface of the media or 4 inches below the media surface. Liners were
planted in the 3 gal containers with the crown also 4 inches below the media
surface. The bottom of the deeply planted liners were either on the bottom
of the 1 gal container or 8 inches above the container bottom for the 3
gal container. Treatments were arranged in a RCBD with five blocks per container
treatment. The plants were topdressed with 16 g of 18-3-6 + Mg Osmocote
Custom Blend and grown outside. Irrigation was applied using overhead sprinklers
following normal nursery practive of 0.5" of water per day.
On 6 July 1994, the study was terminated. Shoots and roots were collected
and dried and dry weight determination of both shoot and root tissue and
root:shoot ratio were determined.
Nutrition . Well rooted seedgrown liners of Uniola paniculata
were planted in a 4 pine bark : 1 sand (by volume) media on
15 Mar. 94. The plants were planted with the crowns even with the top of
the media in trade 1-gal (2.8-liter) containers. Fertilizers were applied
at standardized rates of nitrogen, 1.5 or 3 lb N/yd3 on 5 Apr. 1994. The
containers were topdressed with the following nursery fertilizer formulations:
1) 14-7-7 with micronutrients granular quick release formulation (16 or
32 g/container), 2) 18-3-6 with micronutrients (Osmocote Custom Blend) slow
release (13 or 25 g/container), 3) 16-7-12 without micronutrients (Osmocote
slow release) (14 or 28 g/container), or 4) STEP micronutrients 2 lb/yd3
STEP (3 g/container). The control was not topdressed with additional fertilizer,
however, it did receive the normal nursery practice of twice weekly
fertilizer-injected irrigation with 0.5" water/day.
Results and Discussion
Seed germination . Seeds soaked in 100 ppm GA4
had the highest germination percentage 21 days after treatment (DAT) (Table 1). At 21 DAT the emerged seedlings
from the 100 ppm GA4 treatment were judged to be the most desirable.
Seedlings from the 500 ppm GA4 treatment were twisted, caused
by excessive cell elongation. Scarified seeds were observed to have had
swelling equivalent to treatments that received soaking treatments only;
however, scarification was not necessary to promote germination and resulted
in germination no better than the control.
In the follow-up study there was no difference in the germination rates
of any of the treatments (data not shown). The germination rate of the 100
ppm GA4 soak was lower than previously observed. Thiourea did
not improve the germination percentage, although it has been used effcectively
by other researchers to stimulate germination of seeds that require a moistchilling
treatment.
Earlier researchers found that as storeage time increased germination decreased,
showing either increased dormancy or decreased viability and that storage
time is an important consideration. Soaking in 100 ppm GA4 increased
and accelerated germination of freshly harvested seed, and as storage time
increased, germination rate was reduced. Our data supports the use of a
GA4 soak. It appears that Uniola paniculata has a short
span of seed viability in storage and that seed viability in storage and
that seed dormancy was not the cause of poor germination.
Planting depth . Planting depth had a significant influence
on shoot growth (Table 2).
Plants grown with the crown even with the media surface in 1 gal containers
or deep in 3 gal containers had higher shoot weights than plants grown deep
in 1 gal containers. Root dry weight was also affected by planting depth,
the plants grown deep had the lowest root weight. Root to shoot ratios were
similar between the planting depths. However, plants grown in the 1 gal
containers, regardless of planting depth, had root/shoot ratios almost twice
as high as the plants grown in the 3 gal containers.
Although the root/shoot ratios of the plants grown in 1 gal containers were
similar, there were differences in the weights of the dried shoot and root.
The reason for these differences can be related back to the planting depth.
Plants grown in the bottom of these containers are exposed to a perched
water table or zone of media saturation. The media in containers remains
wet under a regime of regular irrigation such as would be followed in a
commercial nursery in the Southeast. Thus, seaoats do not tolerate excessively
wet conditions.
Nutrition . Levels of tissue nutrients were similar in many
cases (Table 3). However, there
were significant effects on shoot dry weights due to fertilizer rate. The
control treatment and the low N rates had higher shoot weights compared
to the high N rates for each formulation (Table 3). As N rate increased
to 3lb/yd3, however, the amount of shoot biomass decreased for all three
fertilizer formulations. The micronutrient-only treatment also resulted
in lower shoot weight.
Conclusions
Uniola paniculata has the potential to become a widely grown nursery
plant in the Southeast. Seeds should be planted soon after harvest in the
fall to ensure highest germination percentages of these seeds. A GA4
preplant soak of the seeds will help more rapid and uniform germination.
Typically on the dunes, the crowns of U. paniculata become buried
by drifting sand, however, burying the crown of
U. paniculata in 1 gal containers reduced the shoot and root weight
of the plant due to the increased moisture in the bottom of the containers.
Reducing the frequency and amount of irrigation would be helpful in encouraging
the maximum growth.
Finally, U. paniculata does not respond like most plants grown in
containers to increased nutrient inputs. High fertilization rates, whether
granular or controlled release, dramatically reduced the shoot weight of
the plant. Nutrient inputs should be maintained at a minimum.
The results of these experiments suggest that, through proper management,
U. paniculata potentially could be a successful crop for nurseries
to grow.
Last Updated 2/1/97
