1. Ontario’s Invasive Plant Species
Durham Master Gardeners
Website:

2. What is an Invasive Species?
According to the Ontario Invasive Plant Council, an Invasive Species is defined as:
Plants introduced to a new ecosystem through human or other activity.
Find an environmental niche and begin to out compete for space, nutrients, and light
No predators, disease or climatic features to keep their populations in check.
“Alien species whose introduction or spread negatively impact native biodiversity, the economy and/or society, including human health.”

3. How Do They Get Here? Human Pathways Natural Pathways
Pathways are the route by which a plant is dispersed, either how they’re introduced, or how they spread once they’re introduced
There are two types of pathways Human and Natural:
Human pathways include: international travel and tourism, trade and recreational activities
Trade
Packing materials (wood pallets). Untreated wood material can often harbour insects that can potentially become invasive
Importation of aquarium & water garden species, can carry invasive insects, snails, plants, fish.
recreational activities
Eco tourism- walking through an infested site and not cleaning off seeds or plant parts before entering an new area can spread species.
ATVs, bikes, trail equipment - like ecotourism it is important to clean equipment after use.
Natural pathways include wind, water, and animals.
Wind – can carry seed from one are too another.
Water – seed dispersal and plant dispersal
Wildlife- spreading seeds, like buckthorn which works as a laxative.
Origin
Native Habitat

4. Horticultural Pathway
New species introduced every year in horticulture industry
Most are harmless garden additions, but a small percentage can escape into native habitats
There are no regulations or legislation that directly address the importation, cultivation, or sale of invasive plant species. Some groups have started to work with the industry on promoting alternatives, and keeping potentially invasive plants contained in gardens, to promote the idea of the “right plant in the right place”

5. Impact of Invasive Plants
A leading cause of biodiversity loss
Alters landscapes and threatens native species
Costly to control spread
May cause serious health problems
Spread rapidly and easily in new areas
Species such as Dog-strangling vine prevent woodlot regeneration and cost woodlot managers $ to control.
Can cause serious health problems. Some species will cause health problems such as giant hogweed, wild parsnip
Displace native plants in parks and other urban settings. impacting recreational areas
Spread rapidly and easily when introduced to new areas making Invasive plant management a high priority, this is one of the reasons the OIPC has been developed.
Most species are not universally invasive, the degree to which they are invasive depends on a number of factors including climatic factors and soil conditions – however, all invasive species share similar qualities, so be on the lookout for any of these qualities as they can be a sign of potential invasiveness – they are adaptable, reproduce quickly, are aggressive, thrive in disturbed ecosystems, and have few to no predators or climatic factors to keep them in check

6. Invasive Trees and Shrubs

7. Manitoba Maple (Acer negundo)
Native tree fast growing short lived
Up to 60 ft tall
Prefers sunlight and adapts to all soil types
Spreads quickly, suckers, grows well in cities

8. Norway Maple (Acer platanoides)
Deciduous tree, 65 – 90 ft tall
Tolerates poor conditions
Heavy seed crop with high germination
Surface roots starve other plants
Inhibits native plant growth
Norway maple (which has many cultivars) is a small to medium sized deciduous tree with a broad, rounded crown. distinguished from other maples because the leaves and twigs ooze milky sap when cut or torn.
15-18m ( ft) in height,. Young bark is smooth and gray-brown in color, with mature bark having firm, tight, intersecting ridges. dark green leaves with five to seven lobes, with the leaves being wider than they are long. Leaves remain green until early November when they will turn a bright yellow; some cultivars, such as Crimson King, are a rich maroon color all summer. It flowers mid to late-April seeds mature in September and are dispersed by wind. They germinate readily, even in dense shade, and seedlings grow quickly it has become one of the most popular trees for city plantings. It was used widely across North America as a replacement for the thousands of street trees lost to Dutch elm disease It is a fast-growing species that is adaptable to a wide variety of urban sites and more tolerant to urban stresses than many native trees.
Many cultivars have been developed The ability of Norway maple to grow in deep shade makes it particularly threatening to native forest habitats. It commonly invades natural areas in cities (some Toronto ravines are now infested), Norway maples have become so good at establishing themselves, the outskirts of many New England cities and large towns have stands of this species and little else
. Seedlings from Norway maple can form a thick mat and will choke out the natural regeneration of other native tree species. The tree is very efficient in using water and nutrients. Since few species of herbaceous plants can exist underneath the solid canopy of a mature Norway maple stand, the soil beneath the trees tends to be bare and subject to erosion. There are indications that this tree also has allelopathic properties that inhibit the growth of other species in its proximity
The best long-term control method is to phase out the use of Norway maple as a street and garden tree, and substitute native trees such as sugar or red maple.

9. Alternatives Sugar Maple Red Maple Burr Oak Red Oak Ohio Buckeye
Butternut

10. Black Alder (Alnus glutinosa)
Shrub or small tree, ft. tall
Rapid grower: 6-7 ft. per year
Prefers very moist, marshy ground
Crowds out native Alders

11. Russian Olive (Elaeagnus angustifolia)
Reproduces by root suckers
Similar appearance to willow
Hardy, grows well near highways
Tolerates road salt, varying water and temperature conditions
The hardy and adaptable Russian olive was typically planted in poor sites and along roadways due to its high drought and salt tolerance and rapid growth. A native of southern Europe through the Himalayas, it is generally single-stemmed with a full crown reaching a height of 3-4 metres. Russian olive is often misidentified as a willow because of its dull green-gray leaves, but is differentiated by its long fruit that matures in autumn, and thorns. It is especially problematic because of its ability to reproduce via root suckers. C. Poltz UNWANTED Russian Olive (Elaeagnus angustifolia)
Trees and Shrubs
showy yellow flowers with spicy scent in fall;

12. European Spindle Tree (Euonomous altus) Winged Euonymus (Euonomous europaeus)
10 – 20 ft. tall shrub or tree
Poisonous fruit
Replaces native species
No natural controls
Winged euonymus is a deciduous shrub introduced to North America as a horticultural species from northeastern Asia. Deciduous shrub that can grow up to 2.5 m in height. 2-4 broad, corky wings along branchesLeaves are dark green, opposite, 2-7 cm long and 1-3 cm wide, and turn bright red in the fall.
Flowers have four greenish-yellow petals. Fruit appear in the fall and are about 1.3 cm long.
it has been used in landscaping, along roadsides as hedges and in foundation plantings. Adaptable and can grow in a variety of habitats.
The bright foliage of the species makes it a popular ornamental plant, It is also commonly known as "burning bush" because of its bright red foliage.
The winged euonymus is able to grow in a variety of soil types and typically found in open woods, disturbed lands and floodplains.
This species behaves well in urban landscapes, but must be maintained, and should not be planted near woodlands because it can escape cultivation and invade the forest understory.
It creates dense thickets that crowd out and shade native plants, as well as threaten habitats such as fields and prairies.
It has no predators in North America.
Can spread widely because the seeds are distributed by birds and wildlife.

13. Alternatives Speckled Alder or Green Alder (both native to Ontario)
Pagoda Dogwood
American Witch hazel
Serviceberry
Common hoptree

14. Non-native Bush Honeysuckle
Shrubs 4 – 6 ft high, showy flowers
No natural controls
High seed count
Fruit provides less nutrients to birds
Releases allopathic chemicals into the soil and forms dense stands
There are over 180 honeysuckle species in the genus Lonicera. These include honeysuckles native to North America, Asia, Europe, Russia and India. Sixteen honeysuckle species are found in Ontario, including ten introduced species. The species are considered invasive in North America, and Ontario in particular, include the Tatarian (Lonicera tatarica), Amur (L. maackii), Morrow, (L. morrowii) and Bells (L.×bella) honeysuckles.
Common feature of invasive honeysuckles are simple, opposite leaves. Showy flowers Thornless branches, they frequently hybridize with each other
Exotic bush honeysuckles can rapidly invade and overtake a site, forming a dense shrub layer that crowds and shades out native plant species. They alter habitats by decreasing light availability, by depleting soil moisture and nutrients, and possibly by releasing toxic chemicals that prevent other plant species from growing in the vicinity. Exotic bush honeysuckles may compete with native bush honeysuckles for pollinators, resulting in reduced seed
Honeysuckle leaves and berries
Invasive honeysuckles can look similar to some of our native honeysuckles particularly when young. They outcompete native honeysuckles and other native shrubs and herbaceous plants, and they impact forest regeneration. These shrubs also reduce the quality of wildlife habitat, particularly for forest dependent song birds. Invasive honeysuckles are not listed on any federal or provincial weed lists.
Amur Honeysuckle (Lonicera maackii)
Bell’s Honeysuckle (Lonicera bella)
Morrow Honeysuckle
(Lonicera morrowii)
Tartarian Honeysuckle (Lonicera tatarica)

15. Invasive Vines

16. English Ivy (Hedera helix)
Perennial evergreen vine
Grows in a wide range of conditions
Can escape from the garden to nearby woodlots
English ivy is a perennial evergreen vine. Mature plants flower throughout the summer and produce fruit in the fall
English ivy has two growth forms. As an immature plant, the stem is a woody vine whereas mature plants look like a shrub
English ivy has been used as an ornamental ground cover since the early 1700’s when it was introduced from Europe, western Asia and northern Africa). Today it is still commonly sold as a garden plant throughout Ontario
English ivy thrives in open-canopy forests but it can grow in a wide range of habitats in either full shade or sunlight
English ivy spreads vegetatively and by seeds

17. Japanese Honeysuckle Vine (Lonicera japonica)
Japanese Honeysuckle Vine is native to Japan and Korea, and was introduced as a horticultural species.
It is a climbing vine that is evergreen to semi-evergreen; the vines reach lengths of 24 metres and grow either by climbing over other vegetation or trailing along the ground.
Pairs of fragrant, tubular fl owers can range in colour from white to yellow and are found at leaf axils along the stem.
This vine can cover and kill trees either by toppling them from the weight of the vines, or by blocking out sunlight.
It spreads rapidly through runners and by long-range seed dispersal by birds and other animals. It out-competes native species for habitat, sunlight, and nutrients.
Climbing Vines
Grows ft long
Will kill trees
No natural controls
High seed count

18. Periwinkle (Vinca Minor)
Creeping, flowering ground cover
Evergreen foliage, waxy leaves
Escapes gardens to woodlands and forests along wetlands and streams
Spreads rapidly
Vinca minor is a vine-like erect or trailing groundcover; mostly evergreen; stems slender. Leaves are opposite, dark green, glossy, oval to lance-shaped, thick-textured; may be variegated it grows vigorously and forms dense and extensive mats along the forest floor, displacing native herbaceous and woody plant species.  This evergreen vine trails 3 to 5 feet or more and grows up to 12 inches tall   It once was a favorite for blanketing gravesites and was commonly called “grave yard grass.”
Flowers are blue, lavender or white, about 1 in. (2.5 cm) across, five petals blunt at tip, arranged in spiral; blooms in spring time. Spreads vegetatively through rhizomes.
Vinca minor was first introduced into North America in the 1700s as an ornamental. It is still commonly sold as an ornamental ground cover.
Vinca minor has escaped cultivation and is invading natural areas throughout Southern Ontario. It inhabits open to shady sites including forests and often escapes from old homesites.
. Native alternatives: partridgeberry (Mitchella repens), Carolina jessamine (Gelsemium sempervirens), wild ginger (Asarum canadense), wintergreen (Gaultheria procumbens)

19. Alternatives Native Honeysuckle Climbing hydrangea American Wisteria
Native Virginia Clematis
Bunchberry (Canadian dogwood)
Fly Honeysuckle (Lonicera Canadensis)
Swamp Fly Honeysuckle (Lonicera oblongifolia)
Northern Bush Honeysuckle (Diervilla lonicera)

20. Perennials

21. Goutweed (Aegopodium podagraria)
Shade tolerant
Spreads by rhizomes
Most common is variegated, but often reverts to green form
Goutweed is native to Eurasia but can now be found in gardens throughout North America. Also referred to as Bishop’s Weed, this perennial groundcover tolerates a wide range of soil conditions including moist areas and disturbed sites. It is highly shade-tolerant and competitive once established, reproducing by seed and spreading by underground stems called rhizomes. It is most commonly found around shrubs in old gardens. Plants grow about 12 inches high with green leaves that are divided into three leaflets. Some cultivars have variegated leaflets that are green near the centre but whitish around their margins. Umbrella-like white flowers appear in mid-summer.

22. Lily of the Valley (Convallaria majalis)
Forms large clumps
Difficult to remove
Displaces native species
Spreads by roots and seeds

23. Oxeye Daisy (Leucanthemum vulgare)
Introduced from Europe in the early 1800’s as a grass seed contaminant, and then spread as an ornamental. Ox-eye daisy is very common in Ontario, and forms dense infestations in pastures, meadows, roadsides, gardens and lawns.
It is a perennial that reproduces both by seed and by underground rhizome, and has coarsely toothed leaves and a large flower head with white petals and a yellow centre.
Some cultivars sold as ‘Shasta Daisy’ are actually Ox-eye Daisy.
Forms dense clumps
Spreads by seeds and creeping rhizome
Host to several viruses
Often mistaken for Shasta Daisy

24. Alternatives Black-eyed Susan Lance-leaved coreopsis
Pale Purple Coneflower
Canada anemone
Canada mayflower
Canada anemone (Anemone Canadensis
Flat-topped aster (Doellingeria umbellata)
Canada milk vetch (Astragalus canadensis)
White turtlehead (Chelone glabra)
White prairie clover (Dalea candidum)
Ox-eye (Heliopsis helianthoides)
Black-eyed Susan (Rudbeckia hirta)
Lance-leaved coreopsis (Coreopsis lanceolata)
Pale Purple Coneflower (Echinacea pallida)
Canada mayflower (Maianthemum canadense)

25. Invasive Weeds

26. European Buckthorn (Rhamnus cathartica)
Small shrub or tree 6 – 35 ft. tall sharp thorns
Thrives in a wide range of conditions
First to leaf out and last to drop leaves
Birds carry the seeds
Common buckthorn is both drought and shade tolerant, and can grow in a variety of habitats including open woods, thickets on exposed rocky sites, in fencerows, abandoned fields and road edges. . The shrubs have low, wide-spreading, and loosely -branched crowns.
It is found on well-drained sands, clays, and poorly-drained soils, but prefers neutral to alkaline soils. Glossy buckthorn prefers wetter, less shaded areas and has become a problem in wetland sites as varied as sphagnum bogs, calcareous fens, sedge meadows and tamarack swamps. Buckthorn is noted for prolific reproduction by seed. Under full sun conditions, it can produce seed a few years after establishment. Seedlings establish best in high light conditions, but can also germinate and grow in the shade. The seedlings have very rapid growth rates and resprout vigorously after cutting. Buckthorn seed germination is reduced under shading by mature shrubs; however, a carpet of germinating buckthorn seedlings usually appears after mature shrubs are removed.
Ecological Impact Common and glossy buckthorns’ popularity for use as shrubs in hedges resulted in widespread planting across the country, and their invasion of a variety of natural areas. Once established they can spread very quickly, creating a thick cover that will shade out native shrubs and plants. Dense even-aged buckthorn stands will prevent natural regeneration of native trees and shrubs. Buckthorn may also be allelopathic (e.g. its root-exuded chemicals can harm other species and prevent them from growing nearby), which means that once established, natural areas can contain almost exclusively buckthorn.

27. Dog Strangling Vine (Cymanchum rossicum)
Twining vine, up to 6 ft. in height, extremely fast grower
Prefers sun but will grow in shade
No control methods to stop it
Killing forests as it spreads
Threatening Monarch Butterfly
Dog-strangling Vine is an invasive perennial herbaceous plant in the milkweed family (Asclepiadaceae) It forms thick mats of vegetation which hinder recreational activities, choke out native species, and negatively impact managed woodlots.
Dog-strangling Vine grows in a wide range of habitats and spreads quickly along roadsides,
ditches and fence lines. Its seeds are spread short distances by wind or long distances by moving machinery or equipment with seeds attached. Seeds may also spread by falling in to moving water and floating downstream. It is a perennial herbaceous plant with a woody rootstalk that can grow to heights of cm (24-80”) or more.
The stems can be somewhat downy (fine hairs) and they can twine or climb (dependent on available structures such as trees). The stems will also twine around themselves, forming dense mats of vegetation. Deer and other browsers avoid Dog-strangling Vine

28. Garlic Mustard (Alliaria petiolate)
Biennial, 1 – 4 ft. tall (introduced as culinary herb)
First year basal rosettes of round, toothed leaves that smell like garlic
Second year white flower clusters in spring
Has spread to woodlands and flood plains, inhibiting growth of native species
Prolific seed producer, spread by wildlife
Garlic mustard is native to Europe and was introduced to North America in the late 1800’s by early settlers.
It is a cool season biennial herb, with all plants that survive the winter producing flowers and seeds in the second year.
The new leaves smell like garlic when crushed; however, this scent fades as the plant matures.
Garlic mustard was historically eaten as a potherb green, especially during winter and early spring.
It was used for treating gangrene and ulcers, it has high vitamin A and C content.
first year the plant has a basal rosette (cluster of three or four leaves) of dark green and kidney-shaped leaves
second year,
the plant has triangular and sharply- toothed leaves, 3-8cm (1-3in) diameter, alternating on the stem.
Several white flowers (four petals per flower) are at the top of the second-year plant stems
Garlic mustard grows up to 1m (3ft) in height and is the only tall plant in our woodlands with white flowers in May It can self-pollinate
cut or pulled flower stems can still form viable seeds if left laying on the ground
A clump can produce more than 62,000 seeds per square metre. And the seed may remain viable in the soil for up to thirty years.
Garlic mustard produces several phytotoxic chemicals affecting nearby native plants

29. Himalayan Balsam (Impatiens glandulifera)
Annual herb, up to 2 m tall
Prefers moist or wet soils
Creates dense stands
Seed capsules explode when touched covering as much as 5 m
Often mistaken for native Jewelweed
The flowers of Himalayan balsam are irregular and trumpet-shaped (Fig. 133). They range in colour from dark pink to white and grow in clusters of 3 to 12 flowers Seeds are found within green capsules (Fig. 135). When ripe, these capsules burst open at the slightest touch to disperse 4 to 16 seeds
Himalayan balsam can grow in a wide variety of habitats. It has become a particularly troublesome invader along riparian areas, wetlands and forest understories
. Himalayan balsam has a very shallow root system
Prevention strAteGies • Himalayan balsam can easily become established in areas where soil has been disturbed. Limit soil disturbing activities in the woodlot and plant native vegetation in areas where soil disturbance is unavoidable; • If a river or stream runs through the woodlot, ensure that populations of Himalayan balsam are controlled upstream to prevent seed dispersal; • Talk with neighbours about the potential consequences of using Himalayan balsam as a garden plant and suggest some native alternatives.
eArly detection techniques • Learn how to identify Himalayan balsam; • Monitor the woodlot frequently paying attention to disturbed areas and along waterways; • Become familiar with Himalayan balsam in neighbouring gardens.
5.1.7 HIMALAYAN BALSAM (Impatiens glandulifera)
[ ] 129
which allows plants to be easily pulled from the soil. Even with a shallow root system, hand-pulling Himalayan balsam will create soil disturbance. Consider planting native vegetation to prevent re-colonization or invasion by other problematic species
Native Jewelweed

30. Japanese Knotweed (Fallopia japonica)
Aggressive, semi-woody perennial 6 – 25 ft high
Spreads by rhizome and seed
Can be mistaken for Bamboo
Prefers moist to wet soil, but tolerates drier conditions
One of the world’s most invasive species
Will grow through concrete, asphalt, and tear siding off of buildings
This plant requires a sunny environment and grows in a wide variety of soil types and moisture regimes – commonly growing on roadsides, rail-beds, stream-banks, old homesteads, and woodland edges. This is an aggressive plant that forms dense thickets; it displaces native species and threatens habitat, and the shoots and roots have been known n to break through asphalt and concrete.
Control This plant is aggressive and persistent, with no single known method for completely controlling it. It has been reported that repetitive cutting of the shoots as they appear may work over a period of several years11; it must be done two to three times per growing season for as long as 10 years. Application of herbicide to cut stems is reported to be most effective. Japanese knotweed appears on the label of several glyphosate*-based herbicides

31. Purple Loosestrife (Lythrum salicaria)
Wetland perennial 2.4 metres high and 1.5 metres wide
Underground rhizomes can produce stems on one root
Plants can produce over 2.7 million seeds each
Purple loosestrife is a wetland plant native to Europe and Asia that was brought to North America the early 19thcentury
This highly invasive plant was likely introduced when its seeds were included in soil used as ballast 
It forms dense stands with thick mats of roots that can extend over vast areas. 
 Each plant can grow as many as 30 flowering stems that can produce up to 2.7 million seeds each year.
The tiny seeds are easily spread by water, wind, wildlife and humans.
In 1992, the Canadian and American governments approved the release of two European leaf-eating beetles, Galerucella calmariensis and G. pusilla. The beetles are natural enemies of purple loosestrife and feed primarily on the plant, although they occasionally eat other species of loosestrife. This biological control of purple loosestrife can reduce populations by up to 90 per cent and allow native plants to re-establish. The beetles were widely released in Ontario, and purple loosestrife populations at many of these sites have been significantly reduced.
Degrades habitat for wildlife by crowding out native plants
Leaf eating beetles were imported to eat plants with success rates of up to 90%

32. Reed Mannagrass (Glyceria maxima) Common Reed (Phragmites australis)
Aggressive, perennial grasses
Up to 7m tall
Spread rapidly through rhizomes and root fragments
Prefer full sun to partial shade
Dense, cascading flowers
: Perennial grass, also known as reed or tall manna grass.
Distinguished from other Glyceria spp. by its greater height, ribbed lemmas and size of spikelet.
The stems and leaves are also typically wider. likes shallow and deep marshes, wet meadows, bogs, shallow water.
primarily reproduces vegetatively via rhizomes 

34. Giant Hogweed (Heracleum mantegazzianum)
Perennial, up to 5.5 m high, flowers up to 1.2 m across
Seeds slow to germinate, but remain viable for 15 years
Large roots over a metre deep
Flowers once , produces 120,000 seeds per plant, then dies
The sap contains toxins that causes contact dermatitis and severe burns when exposed to sunlight, and blindness
Do not burn as smoke is toxic
Giant Hogweed was originally introduced as a garden ornamental because of its stature and large leaves. It has escaped cultivation across Ontario and was added to Ontario’s Noxious Weeds List in 2010 due to concerns over its threat to human health.
The sap can cause burning and blistering of the skin through toxins (photo-sensitising furanocoumarins) .
This plant is on the Noxious Weeds List, it is no longer sold, and control programs have been put in place in many locations.

35. Wild Parsnip (Pastinaca sativa)
Biennial, with edible roots
First year basal rosette with fern-like foliage
Second year yellowish-green flower clusters up to 1.5m tall and 20 cm across
Sap can cause severe burns
Wild parsnip was likely brought to North America by European settlers, who grew it for its edible root.
Since its introduction, wild parsnip has escaped from cultivated gardens and spread across the continent.
Wild parsnip roots are edible, but the sap of the plant can cause severe burns. Collecting the plant from the wild should only be done with extreme care. See the section Protective Clothing below.
Wild Parsnip is a highly branched plant, with hollow green stems. It has two growth stages: non-flowering leafy rosettes at ground level and 0.5 to 1.5 metre-tall flowering plants.
Wild parsnip, which is also known as poison parsnip, is a member of the carrot/parsley family. It typically grows a low, spindly rosette of leaves in the first year while the root develops. In the second year it flowers on a tall stalk and then dies.
The plant can form dense stands and spreads quickly in disturbed areas such as abandoned yards, waste dumps, meadows, open fields, roadsides and railway embankments. Its seeds are easily dispersed by wind and water, and on mowing or other equipment.
Like giant hogweed and other members of the carrot family, it produces sap containing chemicals that can cause human skin to react to sunlight, resulting in intense burns, rashes or blisters.

36. Questions?