The Role of Public Gardens as

Sentinels of Plant Invasion

Theresa Culley, Kurt Dreisilker, Clair Ryan, Hans
Landel, Nadia Cavallin, Jessica Arcate Schuler, Brittany
Shultz, Roger Gettig, and Kayri Havens
 USDA Forest Service (2005)

Only a very small number of introduced plants become invasive!

Many traits associated with invasiveness are also
desired for horticulture
• Wide ecological tolerance / hardiness
• Rapid growth
• Prolific flowering
• High fruit production (for wildlife)
• Multiple introductions
Many traits associated with invasiveness are also
desired for horticulture
• Wide ecological tolerance / hardiness
• Rapid growth
• Prolific flowering
• High fruit production (for wildlife)
• Multiple introductions

Distribution through
ornamental pathway
Horticulture can be a pathway of invasive plant introductions

82% of 235 woody plant species

escaping cultivation in US were used
in landscaping (Reichard 1994)
 Update of Reichard’s (1994) Review

Tziporah Serota
• Woody, herbaceous, and vine taxa (not only woody)
• Focused on the Midwestern US (not entire US)
• 295 species listed as invasive by the Midwest Invasive Plant Network
(IN, IL, IA, MI, MN, MO, OH, WI)
 Update of Reichard’s (1994) Review

Tziporah Serota
• Woody, herbaceous, and vine taxa (not only woody)
• Focused on the Midwestern US (not entire US)
• 295 species listed as invasive by the Midwest Invasive Plant Network
(IN, IL, IA, MI, MN, MO, OH, WI)

• Determined origin as:

Accidental Ornamental
Agricultural * Some species had
Culinary/medicinal multiple origins
Intentional Aquarium
Soil erosion control
 0%
Intentional Accidental Unknown
Update of Reichard’s (1994)
Mode of Review
Introduction
Ornamental Erosion
Aquarium Medicinal/Herb/Culinary
Feed(Cattle/Wildlife)
 40% 0%

Percentage of Herbace
Intentional Accidental Unknown
30% Update of Reichard’s (1994)
Mode of Review
Introduction
20% Ornamental Erosion
Aquarium Medicinal/Herb/Culinary
10% Feed(Cattle/Wildlife)

0%

A) 100%
C) 100% Woody Vines Herbaceous
90%
90%
of VineTaxa

80%
80%
Taxa

70%
70%
of Woody

60%
60% 89%
Percentage

50%
50%
Percentage

40%
40%

30%
30%

20%
20%

10%
10%
0%
0%
B) 60% Intentional Accidental Unknown
Mode of Introduction
erbaceous Taxa

Ornamental Erosion
50%
Aquarium Medicinal/Herb/Culinary
Feed(Cattle/Wildlife)

40%
 0%

Percentage of Herbaceous
40%

Percentage of Herbace
Intentional
40% Accidental Unknown
30% Update of Reichard’s (1994)
Mode of Review
Introduction 30%

20% Ornamental Erosion

Reichard Aquarium 20% Medicinal/Herb/Culinary
10%
(1994): 82% Feed(Cattle/Wildlife)
10%

0%

A) 100%
C) 100% Woody 0%
100%
Vines Herbaceous
C)
90%
90%
90%
of VineTaxa

Percentage of VineTaxa
80%
80%
Taxa

80%
70%
70%
70%
of Woody

60%
60% 89% 60%
Percentage

50%
50% 50% 65%
Percentage

40%
40% 40%
30%
30% 30%
20%
20% 20%
10%
10% 10%
0%
0% 0%
B) 60% Intentional Accidental Unknown Intentional Accidental Unknown

Mode of Introduction Mode of Introduction

erbaceous Taxa

Ornamental Erosion Ornamental Erosion

50% Aquarium Medicinal/Herb/Culinary
Aquarium Medicinal/Herb/Culinary
Feed(Cattle/Wildlife) Feed(Cattle/Wildlife)

40%
 0%

HerbaceT
70%
40%

Percentage of Herbaceous
40%

Percentage of Herbace

of Woody
Intentional
40% Accidental Unknown
Update of Reichard’s (1994) Review
60%

30%
Mode of Introduction 30%
50%

Percentage of
30%

Percentage
40%
20% Ornamental Erosion 20%
30%
Reichard Aquarium 20% Medicinal/Herb/Culinary
20%
10%
10%
(1994): 82% Feed(Cattle/Wildlife)
10%
10%

0% 0%
0%
A) 100%
C) 100% Woody 0%
Vines C) 100%
B) 60%
Herbaceous
C) 100%
90% 90%
90%
90%

Percentage of Herbaceous Taxa

Percentage of VineTaxa
of VineTaxa

50%
80%

Percentage of VineTaxa
80%
80%
Taxa

80%
70%
70% 70%
70% 40%
of Woody

60%
60% 89% 60%
60%
Percentage

50% 50%
50% 50% 65% 30%
Percentage

40%
40% 40%
40%
30%
30% 30%
20%
30% 31%
20%
20% 20%
20% 10%
10% 10%
10% 10%
0% 0%0%
0% 0%
60% Intentional Accidental Unknown
B) Intentional Accidental Unknown Intentional Accidental Unknown 100%
C)
Mode of Introduction Mode of Introduction Mode of Introduction
90% Ornamental
erbaceous Taxa

Ornamental Erosion Ornamental Erosion Erosion

50%

ge of VineTaxa
Aquarium Medicinal/Herb/Culinary Aquarium Medicinal/Herb/Culinary Aquarium Medicinal/Herb/Culinary
Feed(Cattle/Wildlife) 80% Feed(Cattle/Wildlife)
Feed(Cattle/Wildlife)

40% 70%

60%
 0%

HerbaceT
70%
40%

Percentage of Herbaceous
40%

Percentage of Herbace

of Woody
Intentional
40% Accidental Unknown
Update of Reichard’s (1994) Review
60%

30%
Mode of Introduction 30%
50%

Percentage of
30%

Percentage
40%
20% Ornamental Erosion 20%
30%
Reichard Aquarium 20% Medicinal/Herb/Culinary
20%
10%
10%
(1994): 82% Feed(Cattle/Wildlife)
10%
10%

0% 0%
0%
A) 100%
C) 100% Woody 0%
Vines C) 100%
B) 60%
Herbaceous
C) 100%
90% 90%
90%
90%

Percentage of Herbaceous Taxa

Percentage of VineTaxa
of VineTaxa

50%
80%

Percentage of VineTaxa
80%
80%
Taxa

80%
70%
70% 70%
70% 40%
of Woody

60%
60% 89% 60%
60%
Percentage

50% 50%
50% 50% 65% 30%
Percentage

40%
40% 40%
40%
30%
30% 30%
20%
30% 31%
20%
20% 20%
20% 10%
10% 10%
10% 10%
0% 0%0%
0% 0%
60% Intentional Accidental Unknown
B) Intentional Accidental Unknown Intentional Accidental Unknown 100%
C)
Mode of Introduction Mode of Introduction Mode of Introduction
90% Ornamental
erbaceous Taxa

Ornamental Erosion Ornamental Erosion Erosion

50%

ge of VineTaxa
Aquarium Medicinal/Herb/Culinary Aquarium Medicinal/Herb/Culinary Aquarium Medicinal/Herb/Culinary

Most woody (93.8%), vines (70.0%), and herbaceous (52.1%) were introduced
Feed(Cattle/Wildlife) Feed(Cattle/Wildlife) 80% Feed(Cattle/Wildlife)

70%
intentionally 40%

60%
Gardens Feature Plants from All Around the World

Chicago Botanic Garden

Arnold Arboretum Morton Arboretum

Botanical Gardens & Arboreta are Ideal for Tracking
Invasives

• Curated living collections

• Staff with unique expertise
• Natural areas
• Staff on the ground constantly monitoring collection
• Accessions labeled, monitored over time
• Historical repository

Source: missouribotanicalgarden.org
Botanical Gardens & Arboreta are Ideal for Tracking
Invasives

Amur Corktree
Many Gardens are Listing, Deaccessioning Problematic Taxa

2016 Survey:
65% of gardens actively remove
non-native plant taxa that spread
from their site of planting
Many Gardens are Listing, Deaccessioning Problematic Taxa

2016 Survey:
65% of gardens actively remove
non-native plant taxa that spread
from their site of planting
An Early Invasive Detection Program for
Botanical Gardens & Arboreta
Public Gardens as Sentinels against Invasive Plants

Creating:

1) Online platform for gardens to

share their information

2) Set of guidelines to help gardens

develop their own standardized lists
 Garden Survey – Proof of Concept

7 gardens participated by sharing

their data:
- Provided lists of invasive, watch,
and/or removed species or
cultivars

- Based on historical & current

collections

- Compared info to state listed taxa

(IL, IN, IA, WI, MN, MI, OH, MO, NY)
 Garden Survey – Proof of Concept

• 736 species or cultivars reported within the 7 gardens as being

problematic or escaping cultivation
Ex. Garden A: 17,469 total taxa, of which 230 are problematic (1.3%)
 Garden Survey – Proof of Concept

• 736 species or cultivars reported within the 7 gardens as being

problematic or escaping cultivation
Ex. Garden A: 17,469 total taxa, of which 230 are problematic (1.3%)

• Some list only ornamentals, others include recognized invasives

- Often found in natural areas or spreading within the garden
- Not always clear if species/cultivar originated in the collection
- Gardens collect different data

Clearly need standardization!

 All 7 Gardens: 7 problematic species
# of 9 states listing

Rhamnus cathartica
(Common buckthorn)

Euonymus alatus Celastrus orbiculatus

(Burning Bush) © C. Barton (Oriental bittersweet)
Lonicera japonica
(Jap. honeysuckle)
None of Acer platanoides
these on: (Norway maple)

Lonicera maackii Frangula alnus

(Amur honeysuckle) (Glossy buckthorn)
 All 7 Gardens: 7 problematic species
# of 9 states listing

Rhamnus cathartica

5 7 9 (Common buckthorn)

Euonymus alatus
6
Celastrus orbiculatus
(Burning Bush) © C. Barton (Oriental bittersweet)
Lonicera japonica
(Jap. honeysuckle)
None of 9 7 Acer platanoides
these on: (Norway maple)

7 Lonicera maackii Frangula alnus

(Glossy buckthorn)
(Amur honeysuckle)
 6 Gardens: 11 problematic species
Berberis thunbergii
(Jap. barberry)
Ailanthus altissima
(Tree of heaven) Morus alba
(White mulberry)

Acer ginnala
(Amur maple)
Lonicera tatarica Clematis terniflora
(Tatarian honeysuckle) (Sweet autumn clematis)

Pyrus calleryana
Phellodendron amurense
(Callery pear) Alnus glutinosa
Hedera helix (English Ivy) Rosa multiflora (Amur cork tree) (Black alder)
(Multiflora rose)
 6 Gardens: 11 problematic species
Berberis thunbergii
(Jap. barberry)
Ailanthus altissima
(Tree of heaven) Morus alba
(White mulberry)

Acer ginnala
MOD (Amur maple)
Lonicera tatarica Clematis terniflora
(Tatarian honeysuckle) (Sweet autumn clematis)

WATCH
HIGH

Pyrus calleryana
Phellodendron amurense
(Callery pear) Alnus glutinosa
Hedera helix (English Ivy) Rosa multiflora (Amur cork tree) (Black alder)
(Multiflora rose)
 6 Gardens: 11 problematic species 8
Berberis thunbergii
(Jap. barberry)
Ailanthus altissima
9 2 (Tree of heaven)
2 Morus alba
(White mulberry)

8 Acer ginnala
MOD (Amur maple) 5
Lonicera tatarica Clematis terniflora
(Tatarian honeysuckle) (Sweet autumn clematis)
4 5 3
2 9
WATCH
HIGH

Pyrus calleryana
Phellodendron amurense
(Callery pear) Alnus glutinosa
Hedera helix (English Ivy) Rosa multiflora (Amur cork tree) (Black alder)
(Multiflora rose)
 5 Gardens: 18 problematic species
© Katrin Wicker
© W. Carter

Fallopia japonica
(Japanese knotweed)
Lythrum salicaria Iris pseudacorus
Euonymus fortunei (Purple loosestrife) (Yellow flag)
(Wintercreeper)

Wisteria sinesis
(Chinese wisteria)

Robinia pseudoacacia
Viburnum opulus
© Gardenia.net
(Black locust)
Ligustrum vulgare
(Common privet) (Guelder-rose)
 5 Gardens: 18 problematic species
© Katrin Wicker
© W. Carter

MOD
HIGH LIMITED Fallopia japonica
(Japanese knotweed)
Lythrum salicaria Iris pseudacorus
Euonymus fortunei (Purple loosestrife) (Yellow flag)
(Wintercreeper)

Wisteria sinesis
(Chinese wisteria)

LIMITED

Robinia pseudoacacia
Viburnum opulus
© Gardenia.net
(Black locust)
Ligustrum vulgare
(Common privet) (Guelder-rose)
 5 Gardens: 18 problematic species
© Katrin Wicker

6 8 6 © W. Carter

9
MOD
HIGH LIMITED Fallopia japonica
(Japanese knotweed)
Lythrum salicaria Iris pseudacorus
(Purple loosestrife) (Yellow flag)
5
Euonymus fortunei
(Wintercreeper)

3
Wisteria sinesis

5 (Chinese wisteria)

LIMITED

2 © Gardenia.net
Robinia pseudoacacia
(Black locust)
Ligustrum vulgare Viburnum opulus
(Common privet) (Guelder-rose)
 4 Gardens: 29 problematic species

Cirsium arvense, C. vulgare

(Canada & bull thistle)

Miscanthus sinensis Spiraea japonica

(Maiden Grass) (Japanese spiraea)
Paulownia tomentosa
(Princess tree) Vinca minor
(Lesser periwinkle)
 4 Gardens: 29 problematic species

MOD

Cirsium arvense, C. vulgare

(Canada & bull thistle)

Miscanthus sinensis Spiraea japonica

(Maiden Grass) (Japanese spiraea)
Paulownia tomentosa
(Princess tree) Vinca minor
(Lesser periwinkle)
 4 Gardens: 29 problematic species

9
4 4 1 MOD

Cirsium arvense, C. vulgare

(Canada & bull thistle)

Miscanthus sinensis
(Maiden Grass)
Spiraea japonica
(Japanese spiraea)
3
Paulownia tomentosa
(Princess tree) Vinca minor
(Lesser periwinkle)
 3 Gardens: 57 problematic species

Myriophyllum spicatum
(Spike watermilfoil)
Buddleja davidii Heracleum mantegazzianum
(Butterfly bush) (Giant hogweed) Koelreuteria paniculata
(Goldenrain tree)

Cytisus scoparius Berberis vulgaris Viburnum plicatum. V.

(Scotch broom) (Common barberry) Elaeagnus angustifolia dilalatum, V. sieboldii
(Russian olive) (Snowball)
 3 Gardens: 57 problematic species

HIGH
WATCH
WATCH
Myriophyllum spicatum
(Spike watermilfoil)
Buddleja davidii Heracleum mantegazzianum
(Butterfly bush) (Giant hogweed) Koelreuteria paniculata
(Goldenrain tree)

HIGH
MOD
Cytisus scoparius Berberis vulgaris Viburnum plicatum. V.
(Scotch broom) (Common barberry) Elaeagnus angustifolia dilalatum, V. sieboldii
(Russian olive) (Snowball)
 3 Gardens: 57 problematic species

0 9
9 1
HIGH
WATCH
WATCH
Myriophyllum spicatum
(Spike watermilfoil)
Buddleja davidii Heracleum mantegazzianum
(Butterfly bush) (Giant hogweed) Koelreuteria paniculata
(Goldenrain tree)
0
1 4 7
HIGH
MOD
Cytisus scoparius Berberis vulgaris Viburnum plicatum. V.
(Scotch broom) (Common barberry) Elaeagnus angustifolia dilalatum, V. sieboldii
(Russian olive) (Snowball)
 2 Gardens: 148 problematic species

Alternanthera philoxeroides
(Aligatorweed)
Zelkova serrata
(Japanese zelkova)
© UAEX.edu
© MOBOT
Magnolia kobus
(Japanese magnolia) Pennisetum alopecuroides
(Foxtail fountaingrass)

Dipsacus laciniatus Eleutherococcus sieboldianus

(Cutleaf teasel) (Five-leaved aralia)
 2 Gardens: 148 problematic species

HIGH

Alternanthera philoxeroides
(Aligatorweed)
Zelkova serrata
(Japanese zelkova)
© UAEX.edu
© MOBOT
Magnolia kobus
(Japanese magnolia) Pennisetum alopecuroides
(Foxtail fountaingrass)
WATCH

Dipsacus laciniatus Eleutherococcus sieboldianus

(Cutleaf teasel) (Five-leaved aralia)
 2 Gardens: 148 problematic species

0 0
0 HIGH 0
Alternanthera philoxeroides
(Aligatorweed)
Zelkova serrata
(Japanese zelkova)
© UAEX.edu

0
© MOBOT
Magnolia kobus
(Japanese magnolia)
8 Pennisetum alopecuroides
(Foxtail fountaingrass)
WATCH

Dipsacus laciniatus Eleutherococcus sieboldianus

(Cutleaf teasel) (Five-leaved aralia)
 Only 1 Garden: 504 problematic species

Hibiscus syriacus
(Rose of Sharon)
Triadica sebiferum
(Chinese tallow tree)

Malus floribunda
(Jap. Flowering crabapple)
Vinca major Schinus terebinthifolius
(Large-leaved periwinkle) (Brazilian peppertree)
 Only 1 Garden: 504 problematic species

MOD
Hibiscus syriacus
(Rose of Sharon)
Triadica sebiferum
(Chinese tallow tree)

Malus floribunda MOD MOD

(Jap. Flowering crabapple)
Vinca major Schinus terebinthifolius
(Large-leaved periwinkle) (Brazilian peppertree)
 Only 1 Garden: 504 problematic species

0 0
0 MOD
Hibiscus syriacus
(Rose of Sharon)
Triadica sebiferum
(Chinese tallow tree)

1 0
Malus floribunda MOD MOD
(Jap. Flowering crabapple)
Vinca major Schinus terebinthifolius
(Large-leaved periwinkle) (Brazilian peppertree)
 CONCLUSIONS

• Most non-native, invasive species introduced intentionally,

and most of those for ornamental purposes
Woody – 89% Reichard: Woody – 82%
Herbaceous - 31%
Vines - 65%
 CONCLUSIONS

• Most non-native, invasive species introduced intentionally,

and most of those for ornamental purposes
Woody – 89% Reichard: Woody – 82%
Herbaceous - 31%
Vines - 65%

• Public gardens can act as sentinels of plant invasion

- Regionality is important
- Some taxa are already listed as invasive or noxious on state lists
- Other taxa have escaped detection until now
- Need to standardize data collection
- Information could be shared more widely