This document summarizes a study that analyzed 12 Florida native plant species for their nitrogen uptake and survivability in rain gardens. The study found that Spiderwort, Tropical Sage, Tickseed, and Fakahatchee Grass contained the highest percentage of nitrogen in their leaves, ranging from 2.4% to 3.1%. Tropical Sage was also found to have the highest survivability based on seedling and flower production and height. Monitoring protocols were developed and applied at three rain garden sites located at schools in the Tampa Bay area to track the plants' growth and nutrient content over time.

1. REU 2014-Plant Selection Process for Use in Rain Gardens
Jabari Lee1, Dr. Maya Trotz2: Ph.D Candidate Ryan Locicero
1. Florida Gulf Coast University; 2. Department of Civil and Environmental Engineering, University of South Florida
For more information about the program visit: http://reu-tier.net. The Research Experience for Undergraduates (REU) Tampa Interdisciplinary Environmental Research (TIER) is funded by the National Science Foundation under award number 1156905.
Abstract
Objectives
Background
Approach
References
Results & Conclusions
 Determining how well each plant species out of 12 being
tested grows in rain gardens.
 Determining which of the 12 plant species uptake the most
nitrogen by analyzing nitrogen content.
1. Plant layouts were created for each rain garden cell to track the growth
(plant height, new growth, and overall health).
Plants are postulated to play a significant role in the long term
removal of phosphorous and nitrogen captured by the soil media
in rain gardens through nutrient uptake (Davis et al., 2006).
Studies have shown that appropriately designed rain gardens are
effective at capturing stormwater runoff and removing excess
nutrients from the water before allowing it to evaporate or
infiltrate back into the ground (Hunt et al., 2012) (Clar et al.,
2009) Currently there is a need to determine which plants are
best suited for rain gardens, a green infrastructure for stormwater
management, in the southeastern part of the United States. This
research focuses on determining nitrogen uptake and plant
survivability of 12 Florida native plant species to determine which
species are best suited for implementing within rain gardens in
the Florida’s Tampa Bay region. The average nitrogen content
(mg N/mg dry weight of plant as a percentage) of the leaves and
stems of each plant species was analyzed using a TN 3000. This
was done for plants prior to installation in a rain garden and after
installation. Monitoring and sampling protocols for installed rain
gardens were developed and used at three field sites located on
middle and high schools in the Tampa Bay region.
The following four species contained the highest percent nitrogen
in the leaves: Spiderwort (Tradescantia ohiensis) 3.1%, Tropical
Sage (Salvia coccinea) 2.9%, Tickseed (Coreopsis leavenworthii)
2.5%, and Fakahatchee Grass (Tripsacum dactyloides) 2.4%. Of
the twelve species monitored in the field the Tropical Sage
survived the most in the three rain gardens.
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
SP FL EH SA SF CF IV HL TD CL SC TO
Average%N
Plant ID
Leaves Stems
Figure 2. (a) Rain garden at Young Middle Magnet School with 3 separate cells & layout of plants in cell 1 (b) initially on 3/22/13
and (c) on 6/16/14.
2. Duplicates of each plant species were
harvested from the rain garden (on 3/22/13 the
plants used as is from the nursery prior to
installation). Each plant was separated to give
two samples of stems with their leaves and
roots, dried to constant weight at 105oC for 24
hours, ground in a coffee grinder, and stored for
sample analysis. Total nitrogen of the solid
sample was determined on a Total Nitrogen
Analyzer (Thermo Electron Corporation TN
3000) & used to compare plants. This was done
in triplicate for each separated ground segment.
Area = 25049 (mg N) + 658.6
R² = 0.9969
1000
1500
2000
2500
3000
3500
4000
4500
5000
5500
0.02 0.05 0.07 0.10 0.12 0.15 0.17 0.20
Area
Total Nitrogen (mg)
Figure 3. Example calibration curve for TN using NIST
certified SRM 1515 - Apple Leaves with 2.25% N
1. Clar, M., Davis, A. P., Hunt, W. F., & Traver, R. G (2006). Bioretention
Technology: Overview Of Current Practice And Future Needs. Journal Of
Environmental Engineering, 109-117
2. Davis, A. P., Shokouhian, M., Sharma, H., & Minami, C. (2006) Water Quality
Improvement through Bioretention Media: Nitrogen and Phosphorous
Removal. Water Environment Research, 78, 284-293.
3. Hunt, W. F., Davis, A. P., & Traver, R. G. (2012) Meeting Hydrologic and
Water Quality Goals through Targeted Bioretention Design. Journal Of
Environmental Engineering, 698-707.
% TN in the leaves and stems of twelve native plants varied
between 0.75% and 3.1% and 1.03% and 3.18%, respectively.
Spiderwort (Tradescantia ohiensis) and Tropical Sage (Salvia
coccinea) had the highest % TN in the leaves while Yellow Canna
Lily (Canna flaccida) had a higher percentage of N in the stems
than the Tropical Sage (Figure 4). Of the 12 species, the Tropical
Sage was ranked highest for survivability (production of seedlings
and flowers, and tallest).
Figure 4. Average % N in Leaves and Stems of Plant Species Used in Rain Garden
a.
b. c.
Cell 1
While other factors like plant availability, cost,
and customer preference determine the plants
used in rain gardens, this work contributes to
quantitative and qualitative data for assessing
the sustainability and performance of rain
gardens. This research developed protocols for
monitoring the plants used in rain gardens and
provided information on quantitative nutrient
uptake based on plant growth. Figure 5. Image of
Tropical Sage
The rain gardens monitored in this study were constructed at
two middle and one high school in the Hillsborough county area.
The rain gardens were constructed as part of the Green Space
Based Learning (GSBL) framework and Urban Stormwater
Management Curricular Unit (USMCU). GSBL framework is
designed around teaching students and their teachers about
green infrastructure. It also engages them by allowing them to
participate in the design and construction of the rain gardens.