Invasives

A species is considered invasive if it has been introduced into the environment where it is not native and that has since become a nuisance through rapid spread, often to the detriment of native species. Invasive species arrived in Ontario generally through people who moved here and brought them from their native country. Information on six particular invasive species can be found below and under the Three Invasive Species Article.

Beware of Invasive Plants

There is perhaps a tendency to mistakenly think of plants as being “rooted in place”. However, their ever increasing ability to travel through direct and indirect human assistance to new habitats both near and far can be a blessing or a curse…depending upon just how successful they are in relocating and the resulting threat that success creates in displacing natural vegetation.

A plant that succeeds at the expense of natural or cultivated vegetation soon becomes identified as an “Invasive Species”. Invasive species are plants that are alien to their new habitat and have biological characteristics such as strong root and reproductive systems and vigorous growth habit that allow them to out- compete and eventually threaten the viability of native or cultivated plants. This can result in reduced biodiversity and alteration of natural habitats that then impact negatively on both native flora and fauna. Native species can be deemed invasive if changing environmental circumstances allow them to overtake other native species within their habitat such as the case with the Manitoba maple which in many areas of Canada is now considered an undesirable “weed tree”.

Invasive species tend to be most problematic in areas that have been “disturbed” through human activity. They become very difficult to control or eradicate through natural means and when the threat to native plant and animal populations, successful cultivation of cash crops or human enjoyment of natural areas is heightened, they become the focus of programs aimed at eradication or at least limiting their spread to other areas.

It is the responsibility of all gardeners to be aware of the “invasive status” of any plant they bring into their gardens and to ensure they do not inadvertently contribute to increasing the level of threat these invasive species bring to the health of our natural species and habitats.

View full article discussing Garlic Mustard, Bindweed and Dog Strangling Vine. While there hasn’t been a sighting of Dog Strangling vine in the highlands it has been located as far north as Bobcaygeon. Be on the lookout and eradicate it early before it becomes a problem.

 

For a more information about invasive species visit the Ontario Invasive Plant Council.

Download the Northern Ontario Grow Me Instead guide here.

There is perhaps a tendency to mistakenly think of plants as being “rooted in place”. However, their ever increasing ability to travel through direct and indirect human assistance to new habitats both near and far can be a blessing or a curse…depending upon just how successful they are in relocating and the resulting threat that success creates in displacing natural vegetation.

A plant that succeeds at the expense of natural or cultivated vegetation soon becomes identified as an “Invasive Species”. Invasive species are plants that are alien to their new habitat and have biological characteristics such as strong root and reproductive systems and vigorous growth habit that allow them to outcompete and eventually threaten the viability of native or cultivated plants. This can result in reduced biodiversity and alteration of natural habitats that then impact negatively on both native flora and fauna. Native species can be deemed invasive if changing environmental circumstances allow them to overtake other native species within their habitat such as the case with the Manitoba maple which in many areas of Canada is now considered an undesirable “weed tree”.

Invasive species tend to be most problematic in areas that have been “disturbed” through human activity. They become very difficult to control or eradicate through natural means and when the threat to native plant and animal populations, successful cultivation of cash crops or human enjoyment of natural areas is heightened, they become the focus of programs aimed at eradication or at least limiting their spread to other areas.

It is the responsibility of all gardeners to be aware of the “invasive status” of any plant they bring into their gardens and to ensure they do not inadvertently contribute to increasing the level of threat these invasive species bring to the health of our natural species and habitats.

The following three invasive species are ones that I personally have struggled with in our home property in Southern Ontario (GTA) and cottage property in Central Ontario (Haliburton). They require constant vigilance in monitoring for new invasions and continuing efforts to control existing infestations. Left unattended they would quickly overrun both our gardens and the natural woodlands and meadows surrounding our properties. We do not use herbicides, but with large infestations that threaten natural areas this option may have to be carefully considered and the risks weighed in order to minimize the damage and contain the spread of these species. Researchers are also looking at biological ways to contain these invasive species and hopefully in the near future we will be able to address the spread of invasive species with less risk to the environment.

 

Garlic Mustard

Scientific Name: Alliaria petiolata
Family Name: Mustard Family (Cruciferae)
Type of Plant: Herbaceous Biennial; Non-native plant introduced by early colonists as a cooking/medicinal herb
Habitat/Culture: Woodlands, forest edges and trails, roadside ditches; highly adaptable in terms of light, soil and moisture requirements
Level of Threat: High

Description – Identifying Characteristics:

Height: up to one metre tall

Spread: 10 – 15 cm.

Stem: Tall with little branching; smooth or with a few simple hairs.

Leaves: First year plants produce dark green rosettes of a few to many leaves; leaves vary in shape from first year obovate (kidney) shaped with broad, rounded tip to second year upper leaves that are narrower and ovate with an acute apex and more deeply serrated, margins arranged alternately

Roots: Shallow fibrous root system that typically has a characteristic s-shaped bend that helps the plant “grab” the soil. Mature plants are however easily uprooted with hand pulling.

Flowers: Small, white, flowers with 4 petals, 3-6mm long and wide; grow predominately at the end of the stem in late spring to early summer. Leaves and flowers have garlic-like smell.

Propagation: Prolific seed producer. Short pedicels bear narrow seedpods that readily dry out in mid-late summer and burst open releasing small black seeds. One plant may produce up to 800 seeds that can remain viable in the soil for up to five years.

Control: Infestations spread rapidly. Control requires early detection and eradication generally through hand pulling. Once established, focus on containment and prevention of further spreading by pulling or cutting before seeds are produced. Careful disposal of pulled plants required due to hardiness of seeds.

 

Bind Weed

Scientific Name: Convolvulus sepium (Hedge Bindweed) C. arvensis (Field Bindweed)
Family Name: Morning Glory Family (Convolvulaceae)
Type of Plant: Vigorous perennial vine. Readily adaptable to disturbed soil areas
Habitat/Culture: Forest edges and trails, abandoned fields, roadside ditches, gardens, lawns
Level of Threat: Low – Medium

Description – Identifying Characteristics:

Height/Spread: Vines grow quickly up to 5 meters; can form dense, tangled mats.

Stem: Long slender, trailing, twining or creeping smooth stems with extensive branching.

Leaves: Arrowhead-shaped (hastate) alternate leaves with prominent lobes at leaf base; 2- 10 cm long, with smooth margins.

Roots: Deep, extensive root and rhizome system. Also capable of rooting from each stem nodule.

Flowers: Resemble miniature white, trumpet shaped ornamental morning glory blooms. Generally appear singly in axils of leaves; flower stalk has two small leaf bracts.

Propagation: Introduced to new area by seeds spread by birds, water, manure or as commercial seed contaminants. Seeds have a hard, impermeable seed coat, and can remain dormant in the soil for over 20 years. Once established spreads rapidly through vigorous roots and rhizomes that can regenerate if top removed.

Control: Very difficult to eradicate. Small new infestations may be controlled through repeated removal of top growth and deep cultivation that depletes root system. Larger established infestations require crop rotation and consideration of careful, repeated application of selected herbicides to destroy root.

 

Dog Strangling Vine

Scientific Name: Vincetoxicum nigrum (L.)
Family Name: Milkweed Family (Asclepiadaceae) (this can confuse Monarch butterflies that require true Milkweed plants for egg laying and survive of larvae)
Type of Plant: Aggressive perennial twining vine that readily adapts to disturbed soil. Tolerates variety of soil and moisture conditions.
Habitat/Culture: Forest edges and trails, fields, fencerows, roadsides, ravines
Level of Threat: Medium – High

Description – Identifying Characteristics:

Height/Spread: Vines grow up to 2 metres.

Stem: Long, herbaceous or woody twining stems that quickly scramble over ground, rocks, and vegetation forming impenetrable masses that “strangle” out other species.

Leaves: Ovate shaped leaves with rounded base and sharply pointed apex. Leaves are opposite (2 per node) with small hairs present on smooth margins and heavy veining on underside.

Roots: Vigorous fleshy, fibrous rootstalk or rhizome becomes more woody with age.

Flowers: Small pink, red-brown to dark maroon/purple flowers that begin in late May and end mid-July.

Propagation: Reproduce by seed and by massive underground root system (rhizomes). Seed is extremely viable once it germinates and the rhizomes can also propagate many new plants. Fruit pods resemble long narrow milkweed pods and release large numbers of parachute seed from mid-August to early-November.

Control: Very difficult to eradicate. Requires vigilant mowing and if possible removal of entire root system. Large aggressive infestations may require carefully considered and controlled use of herbicide Arsenal (preferably by professionals).

 

Resources
Chambers B, Legasy K, Bentley, C. 1996. Forest Plants of Central Ontario, Lone Pine Publishing, Edmonton, Alberta.
Invasive Species Canadian Wildlife Federation  http://www.cwf-fcf.org/en/resources/encyclopedias/invasive-species/
Canadian Wildlife Services – Invasive plants and their biology, impact and control options   http://www.cws-scf.ec.gc.ca/publications/inv/11_e.cfm
Fydon, Andrew. Andy’s Northern Ontario Wildflowers Invasive Plants of Ontario http://www.ontariowildflower.com/invasive_plants.htm#top
Royal Botanical Gardens Invasive Plants http://www.rbg.ca/cbcn/en/projects/invasives/invade1.html
Invasive Plants List http://www.rbg.ca/cbcn/en/projects/invasives/i_list.html
The Ontario Woodlot Association – Invasive Exotic Species in Your Woodlot, S & W Report/FallWinter 2001, Vol. 22 http://www.ont-woodlot-assoc.org/sw_invasive_ex otic.html
Garlic Mustard Wisconsin Family Forests 2009 – Garlic Mustard Identification and Control http://www.in-sitevideo.com/wff/garlicmustard.html
Michigan State University Extension – About Garlic Mustard http://www.ipm.msu.edu/garlicAbout.htm

Bindweed
Garden Wise Online, – Invasive Bindweed – July 2008 http://www.gardenwiseonline.ca/gw/ask-pros/2008/07/18/invasive-bindweed
Ontario Ministry of Agriculture, Food and Rural Affairs – Field Bindweed Fact Sheet http://www.omafra.gov.on.ca/english/crops/facts/01-007.htm

Dog Strangling Vine
Fydon, Andrew. Andy’s Northern Ontario Wildflowers Invasive Plants of Ontario http://ontariowildflowers.com/main/species.php?id=200
Ontario Ministry of Agriculture, Food and Rural Affairs –Dog Strangling Vine – An Invasive Species Creeping into Agricultural Fields http://www.omafra.gov.on.ca/english/crops/field/news/croptalk/2006/ct_0306a7.htm
Ontario Ministry of Agriculture, Food and Rural Affairs – Ontario Weeds – Dog Strangling Vine http://www.omafra.gov.on.ca/english/crops/facts/ontweeds/dogstrangling_vine.htm
Routh, John. Task Force Vice-Chair, Living in Toronto – Have you seen this plant? Dog strangling Vine. http://www.toronto.ca/don/dsv/index.htm

Scientific Name: Lythrum salicaria L.

Common Name: Purple Loosestrife

Family: Lythraceae (Loosestrife)

Type of Plant: Herbaceous Perennial

Usage: Ornamental

Identifying Characteristics:

Stems & roots: Stout plant, erect (24-48in); 4 angled stem can be smooth to fuzzy; long, well-established tap root

Leaves: Smooth, opposite (2 per node) or whorled (3 per node); narrow to narrowly oblong and heart shaped at base; 1.25-4 in long, attach directly to stems; upper leaves & those in the inflorescence alternate (1/node) & smaller than lower leaves

Flowers: Magenta – pink, tightly clustered, dense, terminal spikes from 4-20in; sepals united into a column with 8-12 prominent green veins & ending in several, long, thin, pointed lobes; 5-7 petals approx. 1/4in long; several stamens & 1 pistil; small seedpod. Bloom late June – mid Sept. Many garden species previously thought to be sterile can produce seeds by cross pollination with wild & other species, increasing the opportunities for spreading

Habitat: In the wild – wetlands, sedge meadows, open bogs. Can also occur along streams, riverbanks, lake shores. Opportunistic in areas with recent soil disturbance. Grows best in highly organic soils in full sun

Invasive Potential: Introduced from Europe. 2.7 million seeds per plant annually, highly invasive in wetland areas through wind, birds, animals & humans. Readily establishes itself, crowding out native species. Decrease in biodiversity has far reaching ecological implications including displacing plants & animals, eliminating food & shelter for wildlife, degrading native wetlands, reducing habitat for waterfowl. Native to Eurasia

Control: No effective method except in small, localized growth area where it can be intensively managed. Isolated areas, uproot plant by hand ensuring the removal of all parts of plant including all roots

Other methods of control: cutting, burning where permitted, herbicide application although herbicides can destroy other nearby plants

Biological control using root weevil (Hylobius transversovittatus), 2 specie

s leaf eating beetles (Galerucella pusilla & Galerucella calmariensis) have been approved by Canadian government. Research indicate there is little chance of permanent host transfer as these insects only feast on purple loosestrife

Recommendations: Recommended to dig all cultivars of Purple Loosestrife from the landscape and, according to the Manitoba Purple Loosestrife Project, can best be replaced with Spiked Gayfeather (Liatrus); a native plant with pink, purple or white flowers that is an environmentally safe perennial. It requires full sun to part shade, height up to 1.5-2.5m, hardy to CDA zone 3; blooms midsummer to Sept

 

 

Scientific Name: Lonicera tatarica

Common Name: Tartarian Honeysuckle

Family: Caprifolaceae (Honeysuckle)

Type of Plant: Flowering Deciduous Shrub

Usage: Ornamental

Stems & roots: Woody, multi-stemmed, upright 2-5m; Branches thin, smooth, becoming hollow; Dicotyledon; bark turns pale grey & shreds with age

Leaves: Opposite, ovate, 3-6cm long, short-stalked & blue-green; Smooth, hairless, bluish-green leaves

Flowers: Usually in 2 pairs developing in axils of leaves at end of branches; 2 leaflets beneath each bud pair, 2 sepals above leaflets; Petals pink to crimson, tubular, 2-lipped, 7-20mm long, fragrant. Blooms May-June. Fruit – abundant berries 3mm diameter, joined at base, ripening orange to red that are available in winter for the birds & other wildlife

Habitat: Adaptable to wide range of habitat; open woods, ravines, woodland edges; prefer moist, sunny areas

Invasive Potential: Moderately invasive in Ontario. Replaces native understory species & ground flora thereby changing vegetation structure; impedes forest seedling & natural tree regeneration; spread by birds & mammals dispersing seed. Native Eastern Asia

Control:
Mechanical: less dense infiltrations – pull ensuring all roots removed
Chemical: systemic herbicides such as Roundup are most effective. Another method is to cut off near ground level & apply herbicide
Biological: There are no current biological control methods available
Recommendations: As with most invasive plants it is best to remove and replace. To contain remove seedlings annually as they appear. Widespread dispersion by birds limits effectiveness. Replacement with North American natives such as Spice bush (Lindera benzoin) – hardy to CDA zone 5 or Viburnum – hardy to CDA zone 3

 

 

Scientific Name: Rhamnus frangula L.

Common Name: Glossy Buckthorn

Family: RHAMNACEAE (Buckthorn)

Type of Plant: RBC site consider this plant a deciduous tree but many sites consider it a flowering deciduous shrub

Usage: Ornamental

Identifying Characteristics:
Stems & roots: Most often grow in large shrub habit with a few to several stems shooting up from base; shrubs spreading, loosely branched crowns; Bark grey – brown with prominent, lighter-coloured lenticels (pores in the stem of a woody plant allowing exchange of gases between the plant and the exterior)*. Unusual winter appearance with naked, hairy terminal buds & appealing curved twigs with closely-spaced, prominent leaf scars giving the twigs a bumpy outline against a white snowy backdrop. Tree habit reaches 6-9m high and 26cm diameter

Leaves: Thin, glossy, ovate or elliptic leaves, 3.8-7.6cm long; upper leaf surface shiny; lower surface hairy or smooth with margins that are not toothed – a distinguishing feature from the similar common buckthorn

Flowers: Yellow-green, 4 petals develop in clusters of 2-6 near base of petioles. Plant are dioecious (male & female sex organs on separate plants). Fruits small, black berries 0.6cm in diameter appear singly or in small groups in leaf axils. Fruit is poisonous except to European Starling – primary agent responsible for the spread

Habitat: Prefers range of wetland areas such as marshes and bogs but can grow in upland habitats such as forest, wood edges & old fields. In Ontario, primarily near larger populations

Invasive Potential: Invasive locally in Southern & Eastern Ontario. Rapid spread & ability to invade native wetland areas suggest this will become a serious threat in the future. Detrimental effects include: outcompeting native plants for nutrients, light & moisture; degrading wildlife habitat, serving as host to pests such as crown rust fungus

Control:
Mechanical: Remove isolated plants early before seed production, prescribed burns if permitted by law (may need to do this for several years);
Chemical Control: Best during fall season to lessen risk of affecting non-target plants;
Biological Control: No current biological control methods
Recommendations: As with most invasive plants it is best to remove and replace. As with the Glossy Buckthorn, replacement with same North American natives such as Spice bush (Lindera benzoin) – hardy to CDA zone 5 or Viburnum – hardy to CDA zone 3 is recommended

 

Resources:
* Life Sciences & Allied Applications / Botany definition
Invasive Plants of the US: Plant Conservation Alliance’s Alien Plant Working Group: Environment of Canada: Royal Botanical Gardens: Ontario Food & Agriculture: Ministry of Agriculture, Food & Rural Affairs: Ontario Federation of Anglers & Hunters: Invading Species: Ducks Unlimited; Talk About Wildlife; Alberta:

White tail deer are common in the Highlands; we are living in their preferred habitat of mixed forest with open meadows. We all love to see these exquisite creatures until they start nibbling on our most precious plants, usually our favourites. Deer will eat almost anything if they are hungry, such as the first wild leeks of spring but they much prefer a salad buffet of non-native hostas.

Many gardeners have their own deer-proofing ideas ~ from the bar of soap hanging from a tree to a string of aluminum foil plates waving in the breeze. While some of these may work from time to time there are other strategies that may have a longer lasting effect.

These strategies include avoiding the deer favourite plants and choosing plants that deer generally don’t like.

It may seem like deer will eat anything, but in fact they have distinct preferences. The plants listed below are particular favourites of deer and may draw them into your garden. Unfortunately, our favourites are often deer favourites!

Deer Resistant Plants

Deer have an innate sense of determining what foods are good for them and what is not. They know the poisonous plants to avoid but like humans, there are some plants they just don’t like. Some key points when considering plants:

• if a plant makes them sick or is associated with a bad experience they will avoid it
• how hungry they are … plants they don’t like may become much tastier than before
• some individual deer may like plants that most do not
• deer often avoid plants with a strong fragrance, fuzzy or prickly texture or bitter taste ~ often but not always

This Deer Resistant Plant list is composed from the personal observations of several local residents.

• Allium (Allium)
• Lily of the Valley (Converaria majalis)
• Angel’s Trumpet (Datura)
• Lupins (Lupinus)
• Brown/black eyed Susans (Rudbeckia)
• Lilacs (Syringa vulgarism)
• Butterfly weed (Asclepias)
• Lavender (Lavendula)
• Bleeding Heart (Dicentra spectabilis)
• Daphne (Papyricea)
• Cleome (Cleome)
• Blazing Star (Liatris)
• Cosmos (Cosmos)
• Marigolds (Tagetas)
• Daffodils (Narcissus)
• Monkshood (Aconite)
• Delphinium (Delphinium)
• Nicotiana (Nicotiana)
• Foxglove (Digitalis)
• Peonies (Paeonia Lactiflora)
• Globeflowers (Trollius)
• Rhubarb (Rhubarb)
• Goldenrod (Solidago vigaurea)
• Shasta Daisy (Laucanthemum)
• Iris (Iris)
• Valeriun (Valeriana officinalis)
• Juniper (Juniperas)
• Pines (Pinus)
• Spruce (Picea)

It has been suggested that Deer don’t like fuzzy leaves but they will on occasion eat lambs ears. They also don’t like aromatic plants but have been known to eat Artemesia. Often deer won’t eat prickly plants although they seem to like rosebushes. Deer don’t seem to eat ferns and various grasses and other wild plants which suggests they are good to grow.

These are more suggestions for growing plants that deer would not like to eat.

• ajuga
• alchemilla
• beebalm
• campanula
• catmint
• coneflower
• cranesbill
• cup plant
• euphorbias
• forget me not
• gaillardia
• helianthus
• hellebores
• liatris
• obedient plant
• sun drops
• tickseed
• yarrow

Deer Favourites

It may seem like deer will eat anything, but in fact they have distinct preferences. The plants listed below are particular favourites of deer and may draw them into your garden. Unfortunately our favourites are often deer favourites!

Trees, Shrubs, Vines:

Azaleas (Rhododendron spp.): Both deciduous & evergreen
English Ivy (Hedera helix)
Euonymus (Euonymus)
Fir (Abies spp.)
Hybrid Tea Roses (Rosa odorata hybrids)
Japanese Yews (Taxus cuspidata)
Mountain Ash (Sorbus spp.)

Vegetable Garden Plants:

Beans (Phaseolus spp.)
Blackberries, Raspberries (Rubus spp.)
Broccoli, Cauliflower (Brassica spp.)
Lettuce (Lactuca spp.)
Peas (Pisum satirum)
Strawberries (Fragaria spp.)
Sweet Corn (Zea mays)