Write-up of independent research carried out as an undergraduate.

1. Performance of Native Pennsylvania Wildflowers and Dianthus armeria (Caryophyllaceae) in
North American Green-roof Ecosystems
George E. Tickerhoof III
BIOL 482-001
February 19, 2012

2. 2
ABSTRACT
The rising interest in Green-roofs has led to a need for further research into Green-roofs
in varying parts of the world, in the case of this study, North America. In this study, 3 sites near
Curwensville, Pennsylvania were explored to locate native Pennsylvania wildflowers which
would grow on a green-roof. Sites were selected for their soil-rock ratio, amount of sunlight
received, and presence of wildflowers. All 3 sites were monitored over a period of 3 months,
from June to August 2011. Plants were identified and determined if they were native or
nonnative. Measurements were taken of height, root depth, and root system diameter (the
furthest distance from one side of the roots to the other). Five plants (Erigeron annuus, Solidago
juncea, Fragaria virginiana, Achillea millefolium, and Dianthus armeria) are now candidates for
a green-roof in Pennsylvania based on the results of this study. Additionally, 4 plants (Asclepias
tuberosa, Fragaria vesca, Aquilegia canadensis, and Linaria canadensis) are considered species
of interest due to insufficient data for proper conclusion.
INTRODUCTION
In a world of ever increasing energy costs people across the world search for ways to
save energy in order to save money. One of the ways that has begun to emerge in recent years is
Green-roofs. Germany’s green-roof coverage increases by 13.5 million m2
per year. Many
plants currently used in green-roof ecosystems in North America come from a German list
(Oberndorfer et al. 2007). This means that many plants used are nonnative. According to
Oberndorfer et al. (2007) and Lundholm (2005) plants used in green-roof ecosystems in North
America should be native to the environment of the green-roof. Oberndorfer et al (2007) states
that “further research is needed to identify suitable plant species for living roofs in many other
climatic regions.”

3. 3
The criteria for a plant to be considered for a green roof in this study area
: native to
Pennsylvania, grows well in direct sunlight and predominately rocky soil (≥50% rock), has
flexible roots, grow in mixed communities, cannot outcompete other plants, roots must be
≤10cm, and be perennial. Plants that met these criteria were divided into 2 categories: species
of interest and candidate species. Additionally, criteria for a research site to qualify included:
predominately rocky soil, receive full sunlight each day, and presence of wildflowers. A site that
fit all of these criteria were included in the study.
The purpose of this study was to locate native wildflowers that may make suitable
candidates for green-roof ecosystems in Pennsylvania, United States of America.
MATERIALS AND METHODS
Definitions
Root system diameter is the distance from 1 edge of the root system to the other edge of
the roots at the greatest point. Local rarity refers to the circumstance when there were a small
number (≤ 10) of the identified plant present at a given research site. A species of interest is one
that was located, identified, fits most of the criteria, however local rarity prevented complete data
collection. A candidate species is one that was located, identified, fits the criteria, and sufficient
data was collected. Native status refers to whether a plant is native to the United States or not.
Study Area
Study sites were located first near the town of Curwensville, Pennsylvania. The soil
composition, amount of daily sunlight, and the presence of wildflowers were checked. Each site
had mostly rocky soil (≥50%), received full sunlight each day, and contained wildflowers. Three
areas were located, each meeting the criteria as stated earlier. The sites were monitored between
a
Listed in order of importance. Most important is first, least important is last.

4. 4
June and August of 2011. Latitude and longitude of the 4 corners were recorded using Google
Earth (2010).
The pictures above show the 3 research sites. The 2 top pictures depict Site 1, bottom left is
Site 2, and bottom right is Site 3.

5. 5
The pictures above depict an aerial view of the sites. The actual research areas are marked by
the black lines. Top left: Site 1, Top right: Site 2, and Bottom left: Site 3. Image source:
Google Earth.

6. 6
Listed below are latitude and longitude coordinates of each site’s 4 corners.
Site 1
Corner 1 40°53'18.1" N 78°38'47.8" W
Corner 2 40°53'32.8" N 78°38'45.3" W
Corner 3 40°53'30.4" N 78°38'34.3" W
Corner 4 40°53'23.8" N 78°38'36.0" W
Site 3
Corner 1 40°58'44.5" N 78°32'15.1" W
Corner 2 40°58'44.0" N 78°32'14.7" W
Corner 3 40°58'43.7" N 78°32'15.9" W
Corner 4 40°58'43.9" N 78°32'16.2" W
Sampling
After study sites were located the heights of each present species were examined to
determine an approximate range of heights so the shortest and tallest of each species were
included in the study. Then, 10 plants of each species were selected and measured for height,
root depth, and root system diameter when possible. Three plants of each possible species were
removed from their location and replanted in pots to determine if the plants would continue to
grow. Occasionally, local rarity prevented root depth and root system diameter measurement
and collection of specimens to be grown in pots. In a few cases growth method and local rarity
caused the number of measurements to vary from the 10 per plant standard. In these cases, the
maximum number of measurements for height, root depth, and root system diameter were done.
All plants included in the study met the criteria stated previouslyb
.
The percentage of rock and soil in each research site was determined from a sample taken
from each site. The sample was placed in a screen pouch made from the screen from old
window screen material and washed with as little water as possible. This removed the soil from
the rock and was collected in a bucket. The rock and soil were set aside to dry completely.
b
An exception to this was made for Dianthusarmeria, which is nonnative,but included in the study.
Site 2
Corner 1 40°58'39.3" N 78°32'07.3" W
Corner 2 40°58'38.7" N 78°32'07.4" W
Corner 3 40°58'35.7" N 78°32'16.2" W
Corner 4 40°58'35.9" N 78°32'16.7" W

7. 7
When both were dry, each component was weighed. The weights of both components were
added together. The percentage was determined by dividing the weight of the individual
components by the total weight and multiplying by 100.
Data Analysis
Wildflowers were identified using Newcomb’s Wildflower Guide (Newcomb 1977) and
www.mywildflowers.com (Thompson 2011). The native status of each wildflower was then
determined using PLANTS Database (USDA 2011). Native wildflowers were included in the
research, nonnative were excluded from the study, with exception Dianthus armeria. Dianthus
armeria was included due to no negative consequences on ecosystems where it is nonnative to.
RESULTS
Native and nonnative plants were located in each site. Figure 1 shows all plants that were
identified, pictures of each, and their native status.
Erigeron annuus
Native
Echium vulgare
Nonnative
Trifolium agrarium
Nonnative
Centaurea jacea
Nonnative Solidago juncea
Native
Centaurea nigra
Nonnative

8. 8
Linaria canadensis
Native
Dianthus armeria
Nonnative
Lotus corniculatus
Nonnative
Achillea millefolium
Native Fragaria virginiana
Native Melilotus officinalis
Nonnative
Melilotus alba
Nonnative
Asclepias tuberose
Native
Aquilegia canadensis
Native
Figure 1. All of the plants indentified during the research. Pictures, scientific names, and native
status of each are included.

9. 9
The following plants were kept in the research due to where they were found growing
and due to being native, with 1 exception: Erigeron annuus, Dianthus armeriac
, Solidago
juncea, Achillea millefolium, Linaria canadensis, and Fragaria virginiana. Table 2 shows the
presence of the included plants at each of the sites.
Table 2. Presence of included plants at each site
Plant Scientific Name Site 1 Site 2 Site 3
Erigeron annuus Not present Present Present
Dianthus armeria Present Present Not present
Solidago juncea Not present Not present Present
Achillea millefolium Present Present Not present
Fragaria virginiana Not present Not present Present
Linaria canadensis Not present Present Not present
The percentages of soil and rock from each site are shown in Table 3. This data was
collected to determine the composition of the soil. A predominately rocky composition soil was
one of the criteria for the site to be used as well as for the selection of plant selection.
Table 3. Percent soil and rock composition of each site
Site 1 Site 2 Site 3
% Soil 48.7 33.4 9.3
% Rock 51.3 66.6 90.7
The heights of E. annuus, D. armeria, A. millefolium differed slightly from each site
where they were found (Fig. 2). On average E. annuus was the about the same in height in Sites
2 and 3. Dianthus armeria and A. millefolium were nearly twice as tall in Site 2 as in Site 1.
c
Based on use in Jane Perrone’s Green-roof (see Literature Cited section)and no information located suggesting
negative ecosystemeffects.

10. 10
Figure 2. The average heights of Daisy Fleabane (Erigeron annuus), Common Yarrow
(Achillea millefolium), and Deptford Pink (Dianthus armeria) from Sites 1, 2, and 3.
Table 4 shows the height, root depth, and root system diameter measurements of the
remaining plants only found in 1 research site.
Table 4. The average heights of the remaining candidate species
Plant Scientific Name Height (cm) Root Depth (cm) Root System Diameter (cm)
Solidago juncea 49.5 ±3.61 4.99 ±.30 3.29 ±.21
Fragaria virginiana 8.70 ±.53 3.04 ±.27 4.64 ±.71
All plants included in the research met the criteria, including root depth. Table 5 shows
the root depth and root system diameter of 10 specimens of each species (where possible).
Linaria canadensis was a subject of local rarity (only 4 plants were found in the research site).
Achillea millefolium was found to be growing in a colony, therefore root system diameter was
not measured.

11. 11
Table 5. Root depth and root system diameter measurements for all included plants
Plant Scientific Name Root Depth (cm) Root System Diameter (cm)
Achillea millefolium 6.62 ±.83
Dianthus armeria 5.62 ±.83 6.36 ±1.22
Erigeron annuus 4.75 ±.52 6.39 ±.74
Several plants were listed as species of interest. Table 6 lists the plants and reasons for
being a species of interest.
Table 6. Species of interest and reasons to why they are of interest
Plant Scientific Name Reasons
Asclepias tuberosa  Native
 Only 1 specimen found (Site 3)
 Found growing in open, sunny, rocky meadow
 Unable to perform root depth and root system diameter
measurements
Aquilegia canadensis  Native
 Late spring/early summer flowering
 Research began after most plants died for year
 Only 1 specimen found (Site 2)
 Found growing in rocky soil
 Unable to perform root depth and root system diameter
measurements
Linaria canadensis  Native
 Only 4 specimens found (Site 2)
 Found growing in open, sunny, rocky meadow
 Unable to perform root depth and root system diameter
measurements
Fragaria vesca  Native
 Only 2 specimens found (Site 3)
 Found growing in open, sunny, rocky meadow
 Unable to perform root depth and root system diameter
measurements
.
Erigeron annuus, Achillea millefolium, Fragaria virginiana, and Dianthus armeria grew
well in pots. Solidago juncea died 2 days after being placed in pots.

12. 12
DISCUSSION
Perrone (2011) reports using D. armeria on her green-roof, and based on the findings of
this current project, D. armeria appeared to be a good selection for a green-roof. All of the
measurements of all plants included in the research pointed to Dianthus armeria, Achillea
millefolium, Erigeron annuus, Solidago juncea, Fragaria virginiana, and Linaria canadensis
being good possibilities for a green-roof in Pennsylvania. The root depth measurements for
every plant were less than or equal to 10cm (see Table 5), every plant was native with exception
to D. armeria (see Table 1), and finally all included plants were co-dominant with the
surrounding vegetation.
In addition to D. armeria in use on Perrone’s green-roof, E. annuus is used in a green-
roof project, which as of 2006 had 21 specimens growing (Brenneisen 2006). According to New
York City’s park website (c2011) S. juncea is used in their increasing, city-wide green-roof
project. According to the Connecticut Botanical Society, S. juncea grows well in dry, rocky
areas (Connecticut Botanical Society c2005). In one case, F. virginiana began growing on a
green-roof project conducted by Velazquez (2006) without being introduced by humans. In the
case of Velazquez, the F. virginiana was left to grow in the green-roof due to being a food
source to local birds and aesthetics. Fragaria virginiana grows in dry, open areas according to
borealforest.org (2002), lending further evidence in the favor of F. virginiana being used in
green-roof ecosystems. Achillea millefolium is currently described as a candidate by several
online companies such as Green Roof Technology LLC. (c2011). In addition to being described
as a candidate species, according to ARKive (c2003-2012) A. millefolium is drought resistant and
grows in a wide array of soil types.

13. 13
The relatively uniform heights of E. annuus from Site 2 and Site 3 could be explained by
the plant growing equally well in both soil types. The height differences in D. armeria and A.
millefolium between Site 1 and Site 2 could be explained by D. armeria growing better in Site
2’s soil composition. It is also possible that D. armeria and A. millefolium in Site 1 were grazed
by white-tailed deer (Odocoileus virginianus) more heavily when younger than in Site 2. The
failure of growth for S. juncea may be explained by root damage or the excessive heat (33.9°C to
40.5°C) for 7 days after being replanted in pots.
Further research is needed to determine the viability of the species of interest (see table 6)
for a green-roof ecosystem. Oberndorfer et al. (2007) stated native plants are considered ideal
choices as a result of their adaptations to the local climates. My results showed there are native
plants growing in Pennsylvania that are candidates for a green-roof ecosystem.
ACKNOWLEDGEMENTS
I would like to thank Sarah Knight of Curwensville, Pennsylvania for her assistance in
finding research sites, Dr. Timothy Nuttle of the Indiana University of Pennsylvania Biology
Department for his guidance during the research, the Prisk Family of Lumber City, Pennsylvania
for allowing me to conduct research on their property, Sean McGaughran for his time in peer-
editing this paper, and Aletta’s Farm Market of Curwensville, Pennsylvania for the donation of
flower pots.
LITERATURE CITED
ARKive: Yarrow (Achillea millefolium) [Internet]. c2003-2012. Washington (DC): ARKive;
[cited 2012 Feb 18]. Available from: http://www.arkive.org/yarrow/achillea-
millefolium/#text=Habitat

14. 14
Borealforest.org: Common Strawberry, Fragaria virginiana [Internet]. 2002. [Canada]:
borealforest.org; [cited 2012 Feb 18]. Available from:
http://www.borealforest.org/herbs/herb15.htm
Brenneisen S. 2006 Dec. Space for urban wildlife: designing green goofs as habitats in
Switzerland. Urban Habitats [Internet]. [cited 2012 Feb 18]; 4(1):[p 29]. Available
from: http://urbanhabitats.org/v04n01/urbanhabitats_v04n01_pdf.pdf
City of New York Parks & Recreation [Internet]. c2011. New York City (NY): Green roof
species. [cited 2012 Feb 18]. Available from:
http://www.nycgovparks.org/greening/greenbelt-native-plant-center/garden-species-
lists/garden-green-roof
Connecticut Botanical Society: Early Goldenrod [Internet]. c2005. New Haven (CT). [updated
2012 Jan 29; cited 2012 Feb 18]. Available from:
http://www.ct-botanical-society.org/galleries/solidagojunc.html
Deb Thompson: www.mywildflowers.com [Internet]. Pennsylvania: Deb Thompson; [updated
2011 June 25; cited 2011 Aug 25]. Available from:
http://www.mywildflowers.com/index.asp
Green Roof Technology LLC. [Internet]. c2011. Bel Air (MD); [cited 2012 Feb 18]. Available
from: http://www.greenrooftechnology.com/Modern%20Technology/greenroofplants
Google, Inc: Google Earth 6 [Internet]. c2011. Mountain View (CA): Google, Inc; [cited 2011
Aug 24]. Available from: http://www.google.com/earth/download/ge/agree.html
Jane Perrone: horticultural Jane Perrone’s organic gardening blog [Internet]. 2011 Mar 26. Jane
Perrone; [updated 2011 Mar 26, cited 2011 Aug 26]. Available from:
http://perrone.blogs.com/horticultural/2011/03/green-roof-planting.html

15. 15
Lundholm J. 2005. 2.1 Vegetation design and plant communities: a habitat template approach
to green building surfaces. Lundholm J, editor. Greening Rooftops for Sustainable
Communities; 2005 May 4-6; Washington, D.C. Halifax, Nova Scotia, Canada: Saint
Mary’s University. p. 1-14.
Newcomb L. 1977. Newcomb’s wildflower guide. New York: Little, Brown and Company.
Oberndorfer E, Lundholm J, Bass B, Coffman RR, Doshi H, Dunnett N, Gaffin S, Kohler M, Liu
KKY, Rowe B. 2007. Green-roofs as urban ecosystems: ecological structures,
functions, and services. BioScience. 57(10):823-833.
[USDA] United States Department of Agriculture: Plants database [Internet]. Greensboro (NC):
United States Department of Agriculture; [updated 2011 Aug 22; cited 2011 Aug 24].
Available from: http://plants.usda.gov/java/
Linda S. Velazquez: sky gardens [Internet]. 2006, c2007. Atlanta (GA); [updated 2006 Apr;
cited 2012 Feb 18]. Available from: http://www.greenroofs.com/skygardens.htm