Impact Evaluation Report

Washington Conservation Corps Restoration Methods

Washington Department of Ecology 

October 15, 2021

Prepared for: 

Laura Schlabach

WCC IP, Compliance, and 

Communications Coordinator

Washington Conservation Corps 

Washington State Department of 

Ecology PO Box 47600, Olympia, WA 

98504 

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Title-page image: Aerial overview of project site, taken July 2021. 

The Watershed Company Reference Number: 170840

The Watershed Company Contact: Nell Lund, PWS

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TABLE OF CONTENTS

Page #

1 Executive Summary............................................................................ 1

2 Introduction ......................................................................................... 1

3 Purpose ............................................................................................... 2

4 Methods ............................................................................................... 2

4.1 Study Participants........................................................................................... 2

4.2 Site Layout.......................................................................................................3

4.3 Planting and maintenance..............................................................................6

4.4 Data collection ................................................................................................ 7

4.5 Statistical Approach .....................................................................................10

5 Results ............................................................................................... 11

5.1 Native Plant Survival.....................................................................................11

5.2 String Trimmer Damage................................................................................13

5.3 Deer Browse..................................................................................................14

5.4 Cost Estimates ..............................................................................................14

6 Discussion ......................................................................................... 15

7 References ........................................................................................ 17

Appendix A ................................................................................................ 1

Reference Photographs ............................................................................ 1

Appendix A: Photos

LIST OF FIGURES 

Figure 1. Lake Whatcom Watershed map with the City of Bellingham-owned property 

where the restoration area is located marked in pink.......................................... 4 

Figure 2. NWI map showing wetland conditions within the proposed study site. .............. 5 

Figure 3. Outline of study area in black with locations of experimental plots. ................... 6 

Figure 4. Diagram showing approximately layout of experimental plots, center posts, and 

sampling subplots. As shown above, the sub-plot does not need to be precisely 

aligned with the boundaries of the experimental plot. ........................................ 8 

Figure 5. Native plant survival for each treatment over the past 4 years. ........................ 12

Figure 6. Percentage of blue tubes present in each monitoring year................................ 12

Figure 7. String trimmer damage for each treatment in years 1 through 4. ..................... 13
LIST OF TABLES

Table 1. Summer data collection summary for each treatment......................................... 9 

Table 2. Estimated hourly labor costs, 2018-2021............................................................ 10

Table 3. Average native plant survival for each treatment, Years 2018-2021.................. 11

Table 4. Average string trimmer damage in each monitoring year.................................. 13

Table 5. Deer browse for each treatment in each monitoring year. ................................ 14

Table 6. Total costs of installation and maintenance for each treatment in 2018........... 14

Table 7. Total cost for continued maintenance in monitoring years 2 (2019), 3 (2020) and 

4 (2021). .............................................................................................................. 15
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IMPACT EVALUATION REPORT

WASHINGTON CONSERVATION CORPS RESTORATION METHODS

1 EXECUTIVE SUMMARY

The Washington Conservation Corps (WCC) in partnership with City of 

Bellingham, established, maintained and monitored a native plant restoration 

site near Anderson Creek in the Lake Whatcom watershed for a four-year period 

from 2018 through summer 2021. WCC hired The Watershed Company in 2017 

to develop and evaluation plan, including a study design and maintenance and 

monitoring protocols. This study uses a quasi-experimental design with 

randomized control to ascertain correlations between site treatments and plant 

survival. The site treatments applied to native plant live stake are Plantskydd®

application, blue tube installation, and a reference (control). Data collected were 

analyzed using a one-way Analysis of Variance (ANOVA). The approach tested

the null hypothesis that there is no difference between native plant survival, deer 

browse, or stem damage among treatment groups.

The original study spanned one-year and was completed in 2018. Due to the 

short duration of the study and interest in gathering more information about the 

plant establishment period, WCC after coordination with The Watershed 

Company and City of Bellingham, decided to continue the maintenance and 

monitoring protocols an additional three years (2019-2021). The first year (2018) 

showed blue tubes yielded the highest plant survival, lowest string trimmer 

damage, but also the highest cost. This assessment, covering an additional three 

years (2019 – 2021) shows continued and statistically significant high native plant 

survival and low string trimmer damage for the blue tube treatment. The cost 

comparison indicates the blue tube treatment is relatively low cost over the longterm relative to the PlantSkydd® and reference treatments. 

2 INTRODUCTION

The Washington Conservation Corps (WCC) is a service program that has been 

providing opportunities to young adults to protect and restore our natural 

environment since 1983. Improving habitat for state and federally listed species, 

including anadromous fish, is a primary goal of the WCC. WCC projects include 

wetland enhancement and restoration, and riparian corridor enhancement and 
2 

restoration. The Washington State Department of Ecology (Ecology) administers 

the WCC program. Since 1994, WCC has been an AmeriCorps program. 

To comply with AmeriCorps grant requirements and review their internal site 

restoration practices, the Washington Conservation Corps (WCC) hired The 

Watershed Company to prepare an Evaluation Plan in 2017. The WCC chose a 

restoration project they are implementing in partnership with the City of 

Bellingham, Washington. That site was established and monitored by the WCC 

in 2018 and results were reported in the October 2018 Evaluation Report. For this 

current report, a continuation of that project into 2019 through 2021 is evaluated. 

The purpose of this impact evaluation report is to assess the effectiveness of 

different WCC restoration methods spanning a four year period. As the 

independent reviewer, staff from The Watershed Company tabulated and 

analyzed the data WCC crews collected. 

3 PURPOSE

This evaluation seeks to answer the question, “Does additional investment in 

initial restoration techniques and post-restoration care of installed plants lead to 

increase in successful outcomes?” 

More specifically, this study compares the relative benefits of two products 

commonly used to improve plant survival following installation: 1) solid tube 

tree protectors and 2) deer repellant. A literature review did not find any 

comparable studies of wetland native plant survival using these methods; 

however, both tube tree protectors and herbivore repellants have been reviewed 

for protection of agricultural crops (e.g., Zabadal and Dittmer 2000, Olmstead 

and Tarara 2001) and upland trees (e.g., Ward and Williams 2010, Randall 2012). 

This study evaluates the cost-effectiveness of the use of each of these two 

products relative to standard planting methods. The study uses native plant 

survival, evidence of plant damage, and persistence of treatment materials to 

determine the relative cost-effectiveness of each treatment method. 

4 METHODS

4.1 Study Participants

This study was a collaborative project led by WCC, in partnership with the City 

of Bellingham. The City of Bellingham provided the restoration project site, a 
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property owned by the City of Bellingham. Staff from City of Bellingham, WCC, 

and The Watershed Company collaborated on restoration methodologies, study 

questions of interest, and study design. WCC staff was responsible for 

coordination with the City of Bellingham and The Watershed Company. WCC 

supervisors and crew members implemented the planting project, conducted all 

maintenance activities, and collected and compiled field data. City of Bellingham 

and WCC funded the restoration project through a cost-share partnership 

(75/25). WCC funded the evaluation. City of Bellingham contributed staff time 

toward development of the evaluation plan and provided project 

implementation oversight. Staff from The Watershed Company developed the 

Evaluation Plan, assisted with plot set up in 2018, analyzed data provided by 

WCC in 2021, and summarized results in this report. 

4.2 Site Layout

The evaluation was conducted at a 1.04-acre site in unincorporated Whatcom 

County near the City of Bellingham. The site is southeast of Lake Whatcom, in 

the Lake Whatcom Watershed (Figure 1). The restoration site is within a National 

Wetland Inventory (NWI) mapped wetland near Anderson Creek and 

downstream of Mirror Lake (Figure 2). Prior to restoration, the roughly 

rectangular site was initially covered in an existing reed canarygrass 

monoculture (Figure 3). 

The site was divided into 45 experimental plots. The center of each plot was

marked in the field using a sturdy metal or wood stake, marked with the 

assigned plot number (1-45) and treatment (R-reference, D-deer deterrent, or Tprotective tubes). Each experimental plot was approximately 1,000 square feet in 

area. 

One treatment was randomly assigned to each plot using a random number 

generator, until each treatment was assigned to 15 plots. A map of assigned plot 

numbers and treatment locations is shown in Figure 3. 
4 

Figure 1. Lake Whatcom Watershed map with the City of Bellingham-owned property 

where the restoration area is located marked in pink. 
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Figure 2. NWI map showing wetland conditions within the proposed study site. 
6 

Figure 3. Outline of study area in black with locations of experimental plots. 

4.3 Planting and maintenance

The sample plots were established at the beginning of 2018. Maintenance and 

monitoring were completed per plan in 2018. The WCC decided to continue 

maintenance and monitoring in partnership with the City of Bellingham through 

2021 to support a longer-term assessment of treatment options. A single year of 

maintenance and monitoring is insufficient to determine successful plant 

establishment. The restoration goal of native plant establishment requires a 

longer monitoring period, typically three to five years. 

Installation & Year-1 (2018)

The experimental plots were established in winter 2018. Plants were installed on 

January 29th and 30th, 2018. Planting methods, density, and species were

established consistently among all of the experimental plots. Since the site is 

within an NWI mapped wetland, only wet-tolerant native plant species were 

planted. Plants included cottonwoods (Populus balsamifera), willows (Salix spp.), 

red osier dogwoods (Cornus sericea), and spiraea (Spiraea douglasii). All plants 

were installed as stakes. Plants were marked with flagging tape to facilitate 

identification throughout the study period.
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The first round of treatment was applied in winter 2018. Following initial 

planting, each plot was treated according to the treatment assigned. Treatment 

plots were established on January 31st, 2018. For the deer deterrent, Plantskydd®

was applied according to manufacturer specifications immediately following

plant installation (February 6th, 2018) and once in spring during leaf out (April 

23rd, 2018). The central plot posts and measuring tapes were used to identify the 

boundaries of each plot for application purposes. 

Maintenance practices were limited to mowing using a string trimmer, and these 

actions were consistent across the entire site. Mowing occurred on April 20th and 

July 30th through August 2nd, 2018. The second mowing occurred over multiple

working days because crews shut down each day at 1 pm due to elevated 

industrial fire precaution levels at that time. 

Year-2 (2018-2019)

Year-2 maintenance and monitoring were conducted on the same general 

seasonal timeline. The over-winter application of Plantskydd® was done on 

October 24, 2018; the spring application was done April 24, 2019. The entire site 

was brush-cut using string trimmers once in spring (April 15, 2019) and twice in 

summer (July 2, 3 and 8, 2019; and August 12 and 13, 2019). 

Year-3 (2019-2020)

Year-3 maintenance was slightly altered due to COVID-19 pandemic constraints. 

The over-winter application of Plantskydd® was done on schedule in winter on 

December 26, 2019; the spring application was delayed to summer (July 14, 2020) 

due to the global COVID-19 pandemic. Additionally, a mandated statewide 

shutdown delayed brush-cutting in spring 2020. Brush-cutting was done twice in 

summer on July 6 and 9, 2020 and again on September 2 and 3, 2020. 

Year-4 (2020-2021)

Year-4 maintenance and monitoring were back on-schedule. The over-winter 

application of Plantskydd® was done on December 23, 2020; the spring 

application was done April 27, 2021. The entire site was brush-cut using string 

trimmers once in spring (April 23, 2021) and twice in summer (July 16, 2021; and 

August 6, 2021). 

4.4 Data collection

Experimental plots were monitored immediately after plant installation in the 

winter of 2018, and again in the late summer of 2018 through 2021. 

Data collection and monitoring photographs were documented in summer of 

each monitoring year. Data collection for Year-3 (2020) was slightly delayed to 

early September due to pandemic delays. Below are the data collection dates for 

each monitoring year.
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Year-1 (2018) August 15, 2018

Year-2 (2018-2019) August 14, 2019

Year-3 (2019-2020) September 8, 2020 

Year-4 (2020-2021) August 9, 2021

Sampling occurred within a 15-foot by 15-foot sub-plot, as shown in Figure 4. 

When collecting survival plant counts, string trimmer damage counts, and blue 

tube counts, only installed plants with a main stem inside each sub-plot were 

counted. When assessing deer browse, overhanging branches within each subplot were included.

Figure 4. Diagram showing approximately layout of experimental plots, center posts, and 

sampling subplots. As shown above, the sub-plot does not need to be precisely 

aligned with the boundaries of the experimental plot. 

Using a random number generator, two plots of each treatment type were

selected for a permanent photo point. Photo points were taken at the same point 

and direction. Photo-points were recorded in winter and summer of each 

monitoring year. Photo-points were documented at the following plots: 

Reference Deer Repellent Blue Tubes

Plots 22 and 31 Plots 10 and 27 Plots 12 and 14 
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Winter Data Collection 

All native plants within a 15-foot by 15-foot sub-plot near the center of each plot 

were counted immediately following initial installation in 2018 and each winter 

thereafter through winter of 2021 (Figure 4). Winter data collection was limited 

to installed plant counts. A location near the center of each plot was selected to 

minimize the effect of potential drift from adjacent treatments. 

Late Summer Data Collection

Late summer data collection started in late summer of 2018 and continued each 

summer thereafter up through 2021. Late summer monitoring is conducted near 

the end of each annual growing season after the restoration actions and repeated 

each subsequent summer of the monitoring period. Each plot was re-evaluated 

using a 15-foot by 15-foot sub-plot near the center of each plot (Figure 4). Again, 

measuring tapes were used to mark the edges of the 225 SF sample area within 

each plot. Sample areas were located around the central stake in each plot. 

Summer data collection was recorded as summarized in Table 1 below. 

Table 1. Summer data collection summary for each treatment

Data to collect within each 225 SF sub-plot 

by treatment

Treatment

Reference

Deer 

deterrent

Protective 

tube

Installed plant live/dead counts X X X 

Deer browse damage, 1-5 scale estimate X X X 

Percent native plant cover, cover class 

estimate X X X 

Blue tube counts X 

Count of string trimmer damaged plants X X X 

Each living native plant was counted within the sub-plot. Any dead plants 

within the sub-plot were counted separately. 

Evidence of deer browse was qualitatively evaluated in terms of intensity of 

browse damage. In addition, percent native plant cover within the sub-plot was 

visually estimated using the cover class method. 

Where blue tubes were used, the number of blue tubes remaining on each live 

and dead plant within the sub-plot were counted. 

Each plant within the sub-plot was inspected for damage from string trimming. 

The number of plants with string trimmer damage was recorded. 

WCC crews estimated percent cover for native plants in each sub-plot. A Visual 

Cover reference data sheet was used to help standardize cover estimates. 
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Cost 

In order to understand the relative cost effectiveness of each treatment approach, 

the City of Bellingham provided invoices or total costs for all treatment 

materials. The City also provided an estimate of labor hours for each treatment. 

Labor costs are assigned by adding educational award amount and insurance 

costs to the minimum wage for each year. The total annual education award for 

each year was divided by 2080 hours (40 hours x 52 weeks) to estimate an hourly 

cost per staff. Insurance cost used the hourly estimate established in the 2018 

report and an annual 3% cost of living increase was applied in years 2019-2021. 

Labor rate calculations for each year are detailed in the table below. 

Table 2. Estimated hourly labor costs, 2018-2021.

Year

Minimum 

wage

Education 

award Insurance* Total hourly

2018 $ 11.50 $ 2.79 $ 3.71 $ 18.00

2019 $ 12.00 $ 2.85 $ 3.82 $ 18.67

2020 $ 13.50 $ 2.93 $ 3.94 $ 20.37

2021 $ 13.69 $ 2.98 $ 4.05 $ 20.72

* insurance cost assumes a 3% cost of living increase per year.

The cost was estimated in each year by treatment. Annual treatment supply costs 

and field time were provided by WCC for the cost estimates. Time spent 

collecting final annual data in summer of each year was omitted from the cost 

estimate; since this is an artifact of this study. 

4.5 Statistical Approach

The study uses a quasi-experimental design with randomized control to ascertain 

correlations between site treatments and plant survival. The study consists of 

randomized plots, including untreated control (reference) plots as detailed in 

Section 3.2 above. 

Data collected on plant survival, deer browse, and string trimmer damage were 

analyzed using a one-way Analysis of Variance (ANOVA). The approach tested

the null hypothesis that there is no difference between native plant survival, deer 

browse, or stem damage among treatment groups. 

To keep the plot sizes at a practical scale and allow space for necessary replicates 

on the 1.04-acre site, the statistical significance was determined using an alpha of 

0.1. Given the statistical design, a sample size of 15 sites each for a control and 

each treatment provided a power of 0.8 to detect a large effect (f=0.4). 

In addition, we identified the mean percentage of blue tubes remaining on plants 

in the blue tube treatment plots to determine longevity of that treatment method. 
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The survival, browse, and damage measures were compared to the cost of each 

treatment method to provide a cost-benefit comparison among treatments. 

5 RESULTS

The relative performance of each treatment over the 4-year monitoring period is 

summarized below following the established metrics of native plant survival, 

string trimmer damage, and deer browse. Costs associated with the treatments 

over the monitoring period are estimated and summarized. 

5.1 Native Plant Survival

The significantly higher native plant survival noted in year-1 (2018) for the blue 

tube treatment was sustained in years 2 through 4. By the end of year 4 (2021) 

average survival for the blue tube treatment was 74 percent, compared to 42 and 

41 percent respectively for Plantskydd® treatment and the Reference plots 

(Figure 5, p= 0.012). Annual average native plant survival, standard deviations, 

and p-values are summarized in Table 3 below.

Table 3. Average native plant survival for each treatment, Years 2018-2021.

Year 2018 2019 2020 2021

Treatment

Avg. 

Native 

Plant 

Survival

Std 

dev.

Avg. 

Native 

Plant 

Survival

Std 

dev.

Avg. 

Native 

Plant 

Survival

Std 

dev.

Avg. 

Native 

Plant 

Survival

Std 

dev.

Plantskydd® 64% 21% 60% 32% 46% 27% 45% 28%

Blue Tubes 86% 17% 80% 18% 76% 18% 74% 12%

Control 68% 21% 52% 23% 45% 26% 42% 26%

p-value 0.010 0.012 0.012 0.012
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Figure 5. Native plant survival for each treatment over the past 4 years.

Blue Tube Longevity 

In year 1 (2018) nearly 90 percent of blue tubes remained by the August sampling 

period. By year 4 (2021) approximately half of the originally installed blue tubes 

were still present. As the chart below shows, plants with a blue tube exhibited a 

high rate of survival. 

Figure 6. Percentage of blue tubes present in each monitoring year. 

0% 10% 20% 30% 40% 50% 60% 70% 80% 90%

DeerSkydd

Blue Tubes

Control

Native plant survival 2018-2021

2021 Avg. Native Plant Survival 2020 Avg. Native Plant Survival

2019 Avg. Native Plant Survival 2018 Avg. Native Plant Survival

0.0%

10.0%

20.0%

30.0%

40.0%

50.0%

60.0%

70.0%

80.0%

90.0%

100.0%

2018 2019 2020 2021

% native plants that retained blue tube

Blue Tube Longevity

plant w/blue tube live plant w/blue tube
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Plant Survival by Species 

Four different native plant species were installed throughout the sample plots in 

roughly equivalent quantities. Plant species installed in this wetland 

environment were black cottonwood (Populus balsamifera), Hooker’s willow (Salix 

hookeriana), red-osier dogwood (Cornus sericea), and Douglas spiraea (Spiraea 

douglasii). The interaction between plant species survival and treatment method 

is not significant (p = 0.55). 

5.2 String Trimmer Damage

Blue tubes provided statistically significant native plant protection from string 

trimmer damage. String trimmer damage was significantly lower in the blue tube 

treatments compared to the reference and Plantskydd® treatments in all 

monitoring years (p-values in Table 4 below). 

Figure 7. String trimmer damage for each treatment in years 1 through 4.

Table 4. Average string trimmer damage in each monitoring year.

String Trimmer Damage (Avg. # of plants)

Treatment / Yr. 2018 2019 2020 2021

Plantskydd® 2.33 3.00 3.00 5.60

Blue Tubes 0.60 0.87 1.20 2.38

Control 2.07 3.13 5.47 6.78

p-value 0.003 0.000 0.000 0.019

0%

10%

20%

30%

40%

50%

60%

70%

D D D D R R R R T T T T

2018 2019 2020 2021 2018 2019 2020 2021 2018 2019 2020 2021

Native plants with string trimmer damage, 

Years 1-4

2018 D 2019 D 2020 D 2021 D 2018 R 2019 R

2020 R 2021 R 2018 T 2019 T 2020 T 2021 T
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5.3 Deer Browse 

Damage from deer browse remained low among all treatments over the 

monitoring period (3% or less annually). There was no significant difference 

between the frequency of deer browse damage among treatments in years 1 and 

2 (2018 and 2019). However, in years 3 and 4 (2020 and 2021) did yield a 

statistically significant difference among treatments, both p-values are less than 

0.1. Data for years 3 and 4 shows plants in the blue tube plots exhibited more 

deer browse than the Plantskydd® and control treatments (see Table 4 below). 

Table 5. Deer browse for each treatment in each monitoring year.

 Deer Browse (Avg. # of plants)

Treatment 2018 2019 2020 2021

Plantskydd® 0.2 1.7 1.1 0.9

Blue Tubes 0.1 2.4 3.3 2.5

Control 0.3 1.5 1.1 1.1

p-value 0.534 0.273 0.000008 0.0004

5.4 Cost Estimates

Initial start-up cost is highest for the blue tube treatments, both in terms of labor 

and materials compared to both Plantskydd® and reference treatments (Table 5).

The initial year-1 cost estimates assumes 667 plants were planted across all plots 

in each treatment; the total cost per plant surviving to Year 1 is estimated in 

Table 5 below. 

Maintenance over years 2, 3 and 4, show a steady decrease in blue tube treatment 

cost relative to plant survival in the treatment plots. Subsequent costs for years 2 

through 4 are estimated based on materials, labor and plant survival data for 

each treatment (Table 6 below). 

Table 6. Total costs of installation and maintenance for each treatment in 2018.

Reference Plantskydd® Blue Tubes

Materials $701.42 $819.79 $1,354.69

Labor $1,056.00 $1,344.00 $2,136.00

Total $1,757.42 $2,163.79 $3,490.69

Approximate cost per plant surviving Year 1 $3.87 $5.07 $6.09
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Table 7. Total cost for continued maintenance in monitoring years 2 (2019), 3 (2020) and 

4 (2021).

 Reference Plantskydd® Blue Tubes

2019

Materials $0.00 $108.60 $0.00 

Labor $3,584.89 $4,481.11 $3,584.89 

Total $3,584.89 $4,589.71 $3,584.89 

survival counts 78 87 112

Approximate cost per plant surviving Year 2 $45.96 $52.76 $32.01 

2020

 Reference Plantskydd® Blue Tubes

Materials $0.00 $108.60 $0.00 

Labor $1,955.13 $2,932.70 $1,955.13 

Total $1,955.13 $3,041.30 $1,955.13 

survival counts 67 65 106

Approximate cost per plant surviving Year 3 $29.18 $46.79 $18.44 

2021

 Reference Plantskydd® Blue Tubes

Materials $46.89 

Labor $2,354.25 $3,846.38 $2,354.25 

Total $2,354.25 $3,893.27 $2,354.25 

survival counts 63 64 104

Approximate cost per plant surviving Year 4 $37.37 $60.83 $22.64 

Blue tubes are the costliest treatment in Year 1 (2018). However, it is the least 

costly treatment per plant in years two through four (2019-2021). 

6 DISCUSSION

Extending the study protocol to cover four years of plant performance at the 

Anderson Creek Restoration site allows for a greater understanding of how the 

three different restoration treatments (reference, Plantskydd®, blue tube) support 

native plant establishment. Planting site assessments of three to five years, and in 

some cases ten years, more closely follows plant establishment monitoring for 

permitted restoration or mitigation sites. Plant establishment typically takes 

about three years, although environmental stressors can increase the 

establishment period. Plants are commonly large enough to compete with most

invasive plants after at least five years of maintenance. As the site photographs in 

Appendix A show, the restoration plants are still small in stature after four years 

and would benefit from continued maintenance. At this site the primary invasive 
16

plant is reed canarygrass. At sites like this one, the installed plant canopy should 

ultimately shade out the reed canarygrass. Reed canarygrass does not grow as 

vigorously in a shaded environment. 

The blue tube treatment exhibited the highest native plant survival, least string 

trimmer damage, and lowest cumulative costs over the first four years relative to 

use of a deer repellant (Plantskydd®) and the untreated reference plots. Blue 

tubes were lost to the surrounding environment over the monitoring period. 

Approximately half the blue tubes were missing by year 4 (2021). The success of 

the blue tubes should be considered against the environmental impact of 

inadvertently littering this plastic material in the restoration site vicinity. For this 

study, missing blue tubes were not replaced during monitoring and maintenance 

activities. A future study may include an assessment of how many loose blue 

tubes were retrieved from the project area, and thereby kept out of the 

environment long-term. Incorporating blue tube clean up in the maintenance 

protocol would increase labor costs somewhat and alter total costs accordingly. 

Additionally, blue tube removal costs are not accounted for in this assessment. 

When site maintenance is discontinued the blue tubes need to be removed. This 

will increase labor cost in the final year of site work. 

Blue tubes did not protect the plants from deer browse. In fact, the data shows 

slightly higher deer browse in the blue tube plots. In spite of this, overall, blue 

tube treated plots exhibited the highest survival. 

This study shows that the Plantskydd® deer repellant is more costly per plant 

after year 1 relative to blue tubes. The only statistically significant result for deer 

browse over the monitoring period was that deer browse was slightly higher in 

the blue tube plots as noted above. The Plantskydd® treatment requires 

additional material and labor costs but does not yield significantly less deer 

browse than documented in the reference plots. As noted in the year 1 (2018) 

monitoring report, other studies have documented limited effectiveness of the 

Plantskydd® treatment. Other studies of the effectiveness of Plantskydd® have 

found that the repellent effect does not extend beyond one meter from the 

treated area (Nolte and Wagner 2000), so it is unlikely that the close proximity of 

treatments in this study design affected deer browse throughout the study area. 

In order to test this possibility, Plantskydd® could be applied at restoration plots 

with greater separation among plots. 

Although the pandemic caused a delay in maintenance in year 3 (2020), that did 

not appear to generate significant changes in treatment performance. 
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7 REFERENCES

Randall, J. 2012. Tree shelters for hardwood plantings. Iowa State University Extension. 

Nolte, D. and K. Wagner. 2000. Comparing the efficacy of delivery systems and active 

ingredients of deer repellents. P. 93–100 in Proc. of the Nineteenth Vertebrate 

Pest Conference, Salmon, T.P., and A.C. Crabb (eds.). University of California, 

Davis, CA. 

Olmstead, M and J. Tarara. 2001. Physical principles of row covers and grow tubes with 

application to small fruit crops. Small Fruits Review. 1(3)29-46. 

Ward, J. and S. Williams. 2010. Effectiveness of deer repellants in Connecticut. HumanWildlife Interactions. 4(1) 56-66. 

Zabadal, T.J. and T.W. Dittmer. 2000. Grow Tubes: Are They Cost Efficient? 2000 

Research Executive Summaries of the Southwest Michigan Research and 

Agricultural Extension Center. 

Appendix A

Reference Photographs

Direct link to photographs: https://thewatershedcompany.sharefile.com/ds1fd527ef6b4648c9aacf75eb251512a1