Species At Risk

Plants and Lichens at Risk

Many Ontario plants are endangered

When you think of endangered species, you might think first of animals - polar bears, caribou, or birds. But plants are an equally important part of Ontario's biodiversity, and almost a third of the species at risk of disappearing from Ontario are plants.

Ontario's endangered plants include species from trees to water plants and from asters to orchids. They are threatened by loss of habitat, invasive species, and other factors.

Lichens are often confused with plants, but they're actually compound organisms of fungi co-existing with algae or bacteria. Two kinds of lichens are at risk of disappearing from Ontario.

Check out the links below to learn more about Ontario's plants and lichens at risk, including how you can help protect them.


American Chestnut
American Chestnut (Castanea dentata)
People used the American Chestnut for treating numerous ailments (from coughs and dermatitis to heart trouble), as a staple food and beverage, to build shelters, for firewood and as a source of dye. Early settlers soon realized the many important uses of this tree.
American Columbo
American Columbo (Frasera caroliniensis)
American Columbo may live for many years but it flowers only once and then dies.
American Ginseng
American Ginseng (Panax quinquefolius)
Aboriginal people have used American Ginseng for a wide range of medicinal purposes including treatment of headaches, earaches, rheumatism, convulsions, bleeding, fevers, vomiting, tuberculosis, gonorrhea and as a cure-all when other treatments failed.
American Water-willow
American Water-willow (Justicia americana)
American Water-willow (Latin name: Justicia americana) is named after James Justice who was an 18th century Scottish horticulturalist and botanist. “Americana” refers to the plant being native to the Americas.
Bent spike-rush
Bent spike-rush (Eleocharis geniculata)
This plant can store seeds in the soil for years waiting for the right conditions to grow.
Bird's-foot Violet
Bird's-foot Violet (Viola pedata)
Bird’s-foot Violet has a creative way to disperse seeds. The tiny seeds are contained inside a smooth green seedpod that bursts open and flings the seeds up to five metres away.
Blue Ash
Blue Ash (Fraxinus quadrangulata)
special concern
Blue Ash is named for the dye which can be extracted by mashing and cooking the inner trunk bark. It was used by First Nations and early European settlers.
Bluehearts (Buchnera americana)
The seeds of Bluehearts require light to germinate. As a result, the species depends on disturbances such as fire and water level fluctuations to prevent shade-producing vegetation, trees and shrubs from taking over their habitat.
Blunt-lobed Woodsia
Blunt-lobed Woodsia (Woodsia obtusa)
Blunt-lobed Woodsia may live as long as several decades.
Branched Bartonia
Branched Bartonia (Bartonia paniculata)
This plant’s tiny fruits are only about four millimetres long, but each fruit contains 1,000 to 1,500 seeds.
Broad Beech Fern
Broad Beech Fern (Phegopteris hexagonoptera)
special concern
Broad Beech Fern reproduces through spores. The spores are contained in a case-like structure called a sporangium. The sporangia burst upon maturity at the end of summer and the spores are scattered through the air.
Butternut (Juglans cinerea)
Aboriginal people used this plant medicinally to treat toothaches, injuries and digestive problems.
Cherry Birch
Cherry Birch (Betula lenta)
A Cherry Birch tree can live for 265 years or longer.
Climbing Prairie Rose
Climbing Prairie Rose (Rosa setigera)
special concern
Climbing Prairie Rose is dioecious (having male and female reproductive structures on separate plants), which is unusual for rose species.
Colicroot (Aletris farinosa)
Colicroot is also known as “Ague root” because it was used to treat some fevers, which were often referred to as “ague” in Middle English.
Common Hoptree
Common Hoptree (Ptelea trifoliata)
Common Hoptree is one of two native larval host plants for the rare Giant Swallowtail butterfly.
Crooked-stem Aster
Crooked-stem Aster (Symphyotrichum prenanthoides)
Bees and butterflies pollinate the flowers of the Crooked-stem Aster. The seeds are scattered by wind after ripening.
Cucumber Tree
Cucumber Tree (Magnolia acuminata)
The Cucumber Tree gets its name from its fruit that is pickle-like in shape and changes from green to red as it ripens. Once ripe, the oily, scented seeds are exposed and hang by fine threads. It is assumed that birds are the main consumers and dispersers of these seeds.
Deerberry (Vaccinium stamineum)
Efforts are being made at St. Lawrence Islands National Park to re-introduce Deerberry to other areas of the park where the habitat is suitable, in order to increase the overall numbers of the species. Related research is being carried out in partnership with universities.
Dense Blazing Star
Dense Blazing Star (Liatris spicata)
Dense Blazing Star is able to grow in soil that is contaminated with cadmium by turning this toxic heavy metal into a non-toxic form in its tissues.
Drooping Trillium
Drooping Trillium (Trillium flexipes)
Drooping Trillium may take up to 10 years to produce flowers.
Dwarf Hackberry
Dwarf Hackberry (Celtis tenuifolia)
Many insects rely on the Dwarf Hackberry for survival. Several rare insects, including beetles that were only recently discovered in Canada, also depend on the Dwarf Hackberry for part of their life cycles.
Dwarf Lake Iris
Dwarf Lake Iris (Iris lacustris)
special concern
Michigan recently designated the Dwarf Lake Iris as its official wildflower.
Eastern Flowering Dogwood
Eastern Flowering Dogwood (Cornus florida)
The bright red fruit of this tree is poisonous to humans but can be eaten by over 50 species of birds and small mammals. These animals help distribute Eastern Flowering Dogwood seeds throughout forests.
Eastern Prairie Fringed-orchid
Eastern Prairie Fringed-orchid (Platanthera leucophaea)
This orchid’s seeds are produced in huge numbers, but germination and seedling growth depend on the presence of special fungi in the soil.
Eastern Prickly Pear Cactus
Eastern Prickly Pear Cactus (Opuntia humifusa)
Birds sometimes nest among the stems of the Eastern Prickly Pear Cactus, where spines of the cactus aid in protecting eggs and nestlings from predators.
Engelmann's Quillwort
Engelmann's Quillwort (Isoetes engelmannii)
Researchers need to examine this plant under a microscope to tell the difference between different types of quillworts.
False Hop Sedge
False Hop Sedge (Carex lupuliformis)
The tiny flowers of False Hop Sedge are wind pollinated, so the plant does not attract many insects. However, the caterpillars of various butterflies, skippers, and moths feed on various sedge species, while a number of species of birds feed on the seeds.
False Rue-anemone
False Rue-anemone (Enemion biternatum)
Unlike other flowering plants, False Rue-anemone does not produce nectar to attract insects to pollinate its flowers. However, because it is one of the first plants to produce flowers in the spring, it is able to attract insects that don’t yet have tastier options.
Few-flowered Club-rush
Few-flowered Club-rush (Trichophorum planifolium)
All Canadian populations of this plant have been found near openings in the forest canopy, suggesting that once the ground is heavily shaded, this sedge cannot survive.
Forked Three-awned Grass
Forked Three-awned Grass (Aristida basiramea)
Since Forked Three-awned Grass is an annual, its growth and reproduction are influenced by each year’s environmental conditions. This makes estimating population size difficult, as a number of plants present in an area may remain relatively undetectable in the soil seed bank during any given year.
Four-leaved Milkweed
Four-leaved Milkweed (Asclepias quadrifolia)
The two populations of Four-leaved Milkweed which are known to still exist in Ontario were only recently discovered – in 2006 and 2007. It is possible that additional populations may be identified in the future.
Gattinger's Agalinis
Gattinger's Agalinis (Agalinis gattingeri)
Gattinger's Agalinis looks so similar to its close relative, Skinner's Agalinis, that it can only be distinguished by experts who closely analyze specific features of the flowers, leaves and stems.
Goldenseal (Hydrastis canadensis)
A tea made from the roots of Goldenseal was used in traditional aboriginal medicine to treat a variety of complaints including ulcerated or inflamed mucous membranes. This plant continues to be popular in herbal medicine today, but only farm-grown Goldenseal should be used owing to its extreme rarity in the wild.
Green Dragon
Green Dragon (Arisaema dracontium)
special concern
The Green Dragon’s root is bitter tasting and poisonous unless specially prepared, but it was used medicinally by Aboriginal people and European settlers.
Hart's-tongue Fern (Asplenium scolopendrium americanum)
special concern
Hart’s-tongue Fern has very specific habitat requirements, making transplantation and artificial propagation difficult.
Heart-leaved Plantain
Heart-leaved Plantain (Plantago cordata)
Heart-leaved Plantain is capable of self-pollinating but generally the seeds are wind-pollinated.
Hill's Pondweed
Hill's Pondweed (Potamogeton hillii)
special concern
Hill’s Pondweed was not discovered in Ontario until 1951, but a specimen in the Canadian Museum of Nature was collected in 1901. More historical specimens may be discovered in Canadian collections.
Hill's Thistle
Hill's Thistle (Cirsium hillii)
In Ontario, Hill's Thistle often grows with other species at risk such as Lakeside Daisy and Houghton's Goldenrod.
Hoary Mountain-mint
Hoary Mountain-mint (Pycnanthemum incanum)
Hoary Mountain-mint is a very fragrant plant that is attractive to bees and known to produce high quality honey.
Horsetail Spike-rush
Horsetail Spike-rush (Eleocharis equisetoides)
Horsetail Spike-rush was used by the Seminole Indians to make beads for jewelry.
Houghton's Goldenrod
Houghton's Goldenrod (Solidago houghtonii)
Houghton's Goldenrod is thought to have evolved as a result of hybridization between two other goldenrod species and a subsequent increase in chromosome number.
Illinois Tick-trefoil
Illinois Tick-trefoil (Desmodium illinoense)
Illinois Tick-trefoil has explosive blossoms, which means that when a bee or butterfly stops on a flower, a cloud of pollen is shot at it.
Incurved Grizzled Moss
Incurved Grizzled Moss (Ptychomitrium incurvum)
Juniper Sedge
Juniper Sedge (Carex juniperorum)
This species is new to science. The biology of the Juniper Sedge is not well known, since the plant was only discovered in Ontario in the early 1990s.
Kentucky Coffee-tree
Kentucky Coffee-tree (Gymnocladus dioicus)
The leaves and seeds of Kentucky Coffee-tree contain a toxic substance, the alkaloid, cytosine, which may be fatal if consumed. However, aboriginal people used the roasted seeds of the Kentucky Coffee-tree to treat headaches and relieve digestion problems. Roasting is supposed to neutralize the toxins.
Lakeside Daisy
Lakeside Daisy (Tetraneuris herbacea)
The Ontario populations of Lakeside Daisy constitute about 95 per cent of the populations existing in the world. Lakeside Daisy is one of very few plant species with most of its global range in Ontario.
Large Whorled Pogonia
Large Whorled Pogonia (Isotria verticillata)
As do all orchids, Large Whorled Pogonia has a symbiotic relationship with fungus found in the soil, which means they are interdependent for nourishment and survival. The Large Whorled Pogonia will only produce seeds if the necessary fungus is present in the soil.
Nodding Pogonia
Nodding Pogonia (Triphora trianthophora)
Orchids can remain dormant in the soil before emerging when the conditions are suitable.
Ogden's Pondweed
Ogden's Pondweed (Potamogeton ogdenii)
Pondweeds provide habitat for aquatic invertebrates, food for mammals and waterfowl, and hiding places for amphibians and fish.
Pink Milkwort
Pink Milkwort (Polygala incarnata)
Fire plays an important role in maintaining open prairie habitat where Pink Milkwort lives. Fire actually stimulates the growth of these hardy flowers and naturally removes trees and shrubs that would otherwise overtake its habitat
Pitcher's Thistle
Pitcher's Thistle (Cirsium pitcheri)
Pitcher’s Thistle was named after Dr. Zina Pitcher, who discovered the plant while serving as an army surgeon during the 1820s at Fort Brady, Sault Ste. Marie on Lake Superior.
Purple Twayblade
Purple Twayblade (Liparis liliifolia)
Purple Twayblade often grows in grassland savanna – one of the most endangered habitats in Canada. This extremely rare community supports an amazing diversity of wildlife, plants, butterflies and other insects.
Pygmy Pocket Moss
Pygmy Pocket Moss (Fissidens exilis)
special concern
Pygmy Pocket Moss can self-fertilize and produce fertile spores without being in close proximity to other Pygmy Pocket Mosses.
Red Mulberry
Red Mulberry (Morus rubra)
Unlike most fruit trees that are pollinated by insects, the flowers of this plant are pollinated by the wind.
Riddell's Goldenrod
Riddell's Goldenrod (Solidago riddellii)
special concern
Riddell’s Goldenrod has the potential to self-pollinate but it is primarily an out-breeder, pollinated by a variety of flies, bees, wasps, and moths.
Round-leaved Greenbrier
Round-leaved Greenbrier (Smilax rotundifolia)
The seeds of Round-leaved Greenbrier can remain buried in the soil for at least three years while waiting for the right conditions to start growing a new plant.
Scarlet Ammannia
Scarlet Ammannia (Ammannia robusta)
In British Columbia, Scarlet Ammannia is found alongside another species at risk, Toothcup (Rotala ramosior). While these species are also both found in Ontario, they do not occur together here.
Showy Goldenrod
Showy Goldenrod (Solidago speciosa)
threatened (Boreal population), endangered (Great Lakes Plains population)
The root of this species was used by Aboriginal people for burns, strained muscles, trouble breathing and difficult labour.
Shumard Oak
Shumard Oak (Quercus shumardii)
special concern
The Shumard Oak’s shiny, deep-lobed leaves help distinguish the species from the similar-looking Red Oak.
Skinner's Agalinis
Skinner's Agalinis (Agalinis skinneriana)
Skinner's Agalinis is able to steal nutrients from other plants. It uses a fungus to attach its own roots to the roots of its host plant, and is then able to leech nutrients and water out of the plant.
Slender Bush-clover
Slender Bush-clover (Lespedeza virginica)
Fire plays an important roll in maintaining the prairie habitat of Slender Bush-clover. Fire naturally removes trees, shrubs and many invasive plants that would otherwise shade-out prairie plants.
Small White Lady's-slipper
Small White Lady's-slipper (Cypripedium candidum)
Individual Small White Lady’s-slipper plants may not flower until as many as 16 years after germination.
Small Whorled Pogonia
Small Whorled Pogonia (Isotria medeoloides)
The Small Whorled Pogonia appears to be primarily self-pollinated. The flowers lack nectar guides and fragrance and insect pollination has not been observed.
Small-flowered Lipocarpha
Small-flowered Lipocarpha (Lipocarpha micrantha)
This tiny plant has a very wide range. It is found all the way from Brazil to southern Canada, and in Africa.
Spoon-leaved Moss
Spoon-leaved Moss (Bryoandersonia illecebra)
A previously unknown population of Spoon-leaved Moss was discovered in Welland County in 2002.
Spotted Wintergreen
Spotted Wintergreen (Chimaphila maculata)
Aboriginal peoples used Spotted Wintergreen for a variety of medicinal purposes including as a poultice, for rheumatism, and for the treatment of colds and fevers.
Spring Blue-eyed Mary
Spring Blue-eyed Mary (Collinsia verna)
The plant’s flowers are pollinated by bees, butterflies and flies.
Swamp Rose-mallow
Swamp Rose-mallow (Hibiscus moscheutos)
special concern
The total Canadian population of Swamp Rose-mallow is estimated to consist of fewer than 10,000 plants.
Toothcup (Rotala ramosior)
The populations of Toothcup in Canada are believed to be post-glacial relicts - a once widespread natural population surviving only in isolated localities in British Columbia and Ontario because of environmental changes.
Tuberous Indian-plantain
Tuberous Indian-plantain (Arnoglossum plantagineum)
special concern
"Tuberous" refers to the plant’s fleshy, thickened roots.
Virginia Goat's-rue
Virginia Goat's-rue (Tephrosia virginiana)
Virginia Goat's-rue has its own self-defence against pesky insects. The chemical rotenone has been found in the plant, a chemical that is used as an insecticide and piscicide.
Virginia Mallow
Virginia Mallow (Sida hermaphrodita)
In Poland and Russia, this plant is cultivated and used as biomass for creating energy and heat.
Western Silvery Aster
Western Silvery Aster (Symphyotrichum sericeum)
This plant is Ontario's rarest aster, growing in rare bur oak savannahs.
White Prairie Gentian
White Prairie Gentian (Gentiana alba)
Bumblebees are one of the few insects that are strong enough to open the White Prairie Gentian's flowers and pollinate them.
White Wood Aster
White Wood Aster (Eurybia divaricata)
The flowers of White Wood Aster are attractive to butterflies and it is the host plant for Pearly Crescents, a common North American butterfly.
Wild Hyacinth
Wild Hyacinth (Camassia scilloides)
A single Wild Hyacinth can produce over 100 flowers in a single season.
Willowleaf Aster
Willowleaf Aster (Symphyotrichum praealtum)
Aboriginal people used Willowleaf Aster to treat stomach aches and injuries. They also smoked the dried leaves for good luck while hunting.
Wood-poppy (Stylophorum diphyllum)
Wood-poppy seeds have an "elaiosome", which is a fleshy structure that is rich in lipids and proteins. Ants, which are attracted to these elaiosomes, carry them back to their nests, feed them to their larvae, and then discard the intact seed. In doing this, the ants serve as dispersers of the Wood-poppy seeds.


Flooded Jellyskin
Flooded Jellyskin (Leptogium rivulare)
Flooded Jellyskin is considered rare wherever it occurs worldwide.
Pale-bellied Frost Lichen
Pale-bellied Frost Lichen (Physconia subpallida)
This lichen grows on the surface of other plants, rocks, or structures and derives nutrients from the air and rain.