Managing Non-Native &
Invasive Plant Species
Jonathan Kays
University of Maryland Extension
jkays@umd.edu
What is a Native?
• Native
– Thousands of years of co-evolution with other
native plants and animals
• Exotic
– Introduced from other parts of the country or world
– Exists outside of the system that it evolved in
– Not necessarily invasive (1,000 of 4,000)
Non-Native Plants Do Not Support
Wildlife Equally
Non-native vs native
Non-native plants
support fewer insects
Fewer Native Plant Species –
Fewer Insects
Native insects can’t eat nonnatives because foliage
defended by distasteful
chemicals.
The result is fewer insects to
support wildlife populations
Protein From Caterpillars & Insects is
What Supports Reproduction
Not just birds:
Bear – 23% of diet
Red fox – 25% of diet
Rodents
Skunks
Native Plants Just Produce More
Food for Wildlife
80
Number of lepidopteran species
70
60
50
40
30
20
10
0
Native Woody
Non-Native Woody
Many more caterpillar species
on native woody plant genera in
the mid-Atlantic states
Uninvaded
Invaded
22 times fewer caterpillars in
the invaded hedgerows
Invasive v. Non-Invasive
• As per Executive Order 13112 an "invasive
species" is defined as a species that is:
– 1) non-native (or alien) to the ecosystem under
consideration and
– 2) whose introduction causes or is likely to cause
economic or environmental harm or harm to
human health.
Noxious Weeds: defined by MD Weed Control Law, required to be
removed: johnsongrass, shattercane, and thistles
Multiflora Rose
• MD law:
– A person who owns land where multiflora rose is
grown shall maintain the land in accordance with
management techniques prescribed by the
Department to prevent the spread of multiflora
rose to adjoining property used for agricultural
production.
Primer on Invasives
• How they get started
– Imported in packing material or ballast water
– Intentionally introduced: “seemed like a good idea
at the time”
• Erosion control
• Ornamental
Primer on Invasives
• Why they are successful
– Easy to grow
• Quick solution to a problem
• Easy landscaping
• Lack of knowledge of consequences
– Similar to Superman
• No natural enemies
• Easy to compete in the local climate/site
Primer on Invasives
• Their impact
– Damages and losses of more than $138 billion per
year nationally*
– Crowd out native species
– Reduce food and cover sources for native species
– Reduce biodiversity
*Pimentel, D.; R. Zuniga and D., Morrison (2005). "Update on the environmental and
economic costs associated with alien-invasive species in the United States.".
Ecological Economics 52: 273–288. doi:10.1016/j.ecolecon.2004.10.002
Ornamental Plants
• English ivy (Hedera helix)
• Oriental bittersweet
(Celastrus orbiculatus)
• Eulalia, flame grass, zebra
grass (Miscanthus sinensis)
• Burning bush
(Euonymus alatus)
• Japanese Barberry
(Berberis thunbergii)
• Privet (Ligustrum spp)
• Norway maple
(Acer platanoides)
Microstegium vimineum,
Japanese stilt grass
• Used for
packing oriental
porcelain
• Shade tolerant
• Changes soil
conditions
Wavyleaf
Basketgrass
(Oplismenus
hirtellus subsp.
Undulatifolius)
• Sticky seeds
Winged Euonymus/Burning Bush
(Euonymus alatus)
Multiflora Rose
(Rosa multiflora)
Oriental Bittersweet (Clastrus
orbiculatus)
• Can establish in dense shade, grows along
woodland edges, forest gaps
• Competitive advantage over native bittersweet
through photosynthetic efficiency
• Climbs over trees increasing possibility of wind
damage, girdles smaller trees
Lonicera japonica
Japanese honeysuckle
• Introduced to Long Island 1806
• Promoted for ornamental use,
wildlife
• Girdles trees, dense groundcover
• Semi-evergreen to evergreen
Lonicera japonica
Lonicera sempervirens
Polygonum perfoliatum
Mile-a-minute vine
• Accidental introduction in
Rhododendrons from Asia
• Can grow 6”/day
• Found in young forests,
stream edges, fallow fields
Kudzu (Pueraria montana)
Ailanthus altissima
tree of heaven
• Introduced 1748 to Philadelphia
• Chemicals from leaves & roots
hinder growth of other plants
• Aggressive root sprouting
Pyrus calleryana
Callery (Bradford) pear
Taking over old fields
along interstates
Elaegnus umbellata
Autumn olive
•
•
•
•
Introduced 1830 from Asia
Nitrogen fixer
Promoted for wildlife
Berries of marginal value
Lonicera maackii
Amur honeysuckle
• Introduced 1898 to NY
Botanical Garden
• Promoted for wildlife
• Reduces seedling
establishment and herb
richness in forests
• High nest predation
Garlic mustard
• Grows in forest
understories and edges
• Reduces establishment
of tree seedlings
• Threat to survival of rare
butterfly
Pieris
virginiensis
Phragmites australis, common
reed
• Native and non-native strains
– http://www.invasiveplants.net/diagnostic/diagnostic.asp
Control Measures
• Mechanical
– Hand pulling/cutting
•
•
•
•
High labor cost
Low dollar cost
May require repetition
May be ineffective
– Mowing
• Moderate labor
• Moderate dollar cost
• Requires repetition
– Grazing
• High cost
• Good for sites with difficult access
• Good for sensitive sites
Control Measures
• Chemical
–
–
–
–
Labor varies
Higher cost usually
Usually effective
Require care to avoid collateral
damage
• Herbicides are much safer than
insecticides and other pesticides
– Affect growth regulators & hormones
not found in humans
Effective Herbicide Treatments
Success with herbicides requires
• The most effective herbicide
• Glyphosate (Roundup) – Home stores
• Triclopyr (Garlon 3a & 4) – 2.5 gallons
• Applied using the correct method
• Backpack sprayer, hack ‘n squirt, etc.
• Applied during the best time period
• Later summer or fall is usually best, winter for
basal application
Everything you
need to know is on
the label! Read it!
Method and Timing of
Application
• Foliar spray
• Wiping
• Hack-and-squirt or injection
(late winter, summer, not in
spring)
• Cut stump (late winter and
summer)
• Basal bark treatment (late
winter, early spring)
Applying Herbicides to Individual Trees
50% mixture of roundup
Use a good ax
Hack and Squirt
Sprayers
USDA Forest Service – Region 8 Archive
John D. Byrd, Mississippi State University
Controlling Vines
• Cut at base of
tree
• Herbicide usually
not needed
• Vines will dry out
and fall apart
• Remove from
dominant trees.
Keep some vines
for wildlife
Swedish Safety Brush Ax
What you can do!
• Monitor your land
• Choose the best control method
and timing
• Plan for restoration
– Nature abhors a vacuum
– How will you fill the gap?