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Plants

Specially-adapted Plants

Dunes are an extremely harsh environment for plants to grow in. Imagine trying to cultivate a plant in pure sand, leaving it out in the sun without water for days on end, and violently shaking the pot every now and then! Plants of the dunes have had to develop special adaptations for life under conditions like these.

American Beach Grass (Ammophila breviligulata) is usually one of the first species to colonize the dunes. Not only can it tolerate being buried by sand, studies have shown that it requires burial for optimal growth. When the wind meets dune vegetation, its velocity is reduced, causing sand to accumulate. As dune sands bury the grass, it forms new shoots above the sand, while its roots and rhizomes continue to grow deeper and stabilize the sands. Other grasses tolerant of sand burial include Long-leaved Sand Reed (Calamovilfa longifolia var. magna), Little Bluestem (Schizachyrium scoparium) and Great Lakes Wheat Grass (Elymus lanceolatus var. psammophilus). The latter species is an attractive silvery-grey colour, and grows in the more sheltered areas, such as behind the foredunes or in the meadows between the dunes. It also spreads primarily through rhizomes and helps stabilize the dune habitat.

Shrubs that can tolerate a certain amount of burial by sand include Red-osier Dogwood (Cornus stolonifera) and Sand Cherry (Prunus pumila). Balsam Poplar (Populus balsamifera), Eastern Cottonwood (Populus deltoides), Red Cedar (Juniperus virginiana), Common Juniper (J. communis) and Creeping Juniper (J. horizontalis) are other woody species that are able to survive and even thrive in the dune environment. The endangered Pitcher’s Thistle (Cirsium pitcheri) is a long-lived perennial herb that also requires seed burial, and propagates well in areas where the sand has been moved by wind.

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Where North Meets South and East Meets West

The dominant plant species give distinctive character to the many different dune habitats. Variations in vegetation are evident at all scales, from microhabitats such as blowouts, to medium-scale systems such as beach ridges, foredune grasslands, and backdune savannahs and woodlands. The vegetation also changes with latitude. In the Pinery – Grand Bend area at the south end of Lake Huron, many southern or ‘Carolinian’ species occur, while the dunes of the Manitoulin Island area are dominated by plants more characteristic of central Ontario.

At the Pinery, plants in the backdune savannah habitats include southern species such as Black Oak (Quercus velutina), Chinquapin Oak (Q. muhlenbergii), Dwarf Chinquapin Oak (Quercus prinoides), Grey Dogwood (Cornus foemina), Fragrant Sumac (Rhus aromatica) and Red Cedar. However, northern species such as Shrubby Cinquefoil (Potentilla fruticosa) and Buxbaum’s Sedge (Carex buxbaumii) are common in the cooler conditions of the moist meadows between the backdunes, even as far south as the Pinery.

The dune and beach ecosystems of Lake Huron are also host to a number of plants associated with the Atlantic seaboard of North America and the prairies of the west. It is speculated that these eastern and western plants of open habitats colonized the area during the warming period after the last ice age, when barren coastal habitats were more extensive and continuous in the Great Lakes region than they are today. Dune plants considered ‘eastern’ include American Beach Grass and Blue-leaf Willow (Salix myricoides). Western plants occurring on Lake Huron dunes include Fragrant Sumac, Switch Grass (Panicum virgatum), and the provincially rare Porcupine Grass (Stipa spartea) and Plains Puccoon (Lithospermum caroliniense).

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Great Lakes Endemics

Also of interest are endemic plant species, subspecies and varieties that have evolved relatively recently in the Great Lakes basin, including those found almost exclusively on the dune and beach ridge systems. These endemic species are considered rare both globally and provincially. In Ontario, Pitcher’s Thistle is restricted to dune grassland and beach ridge habitats at just a few locations in southern Lake Huron (the Pinery and Inverhuron provincial parks), and a number of sites in the Manitoulin Island area. Isolated populations of Pitcher’s Thistle also occur at Pukaskwa National Park on eastern Lake Superior. Great Lakes Wheat Grass is found at scattered dune and sand beach sites on the Bruce Peninsula and Manitoulin Island. Gillman’s Goldenrod is found at only two locations in all of Ontario, both in the Manitoulin region. Long-leaved Sand Reed is also endemic to the Great Lakes area, with its preferred habitat being sand dunes.

Rare Plant Species

The long list of provincially rare plants found on Lake Huron dunes includes Bugseed (Corispermum hookeri), Fringed Puccoon (Lithospermum incisum), Smooth Sand Sedge (Cyperus houghtonii), Pindrops (Pterospera andromedea), Slender Mountain-mint (Pycnanthemum tenuifolium), Prairie Ragwort (Senecio plattensis), Green Milkweed (Asclepias viridiflora), Rough Blazing-star (Liatris aspera), Cylindrical Blazing-star (Liatris cylindracea), Hill’s Thistle (Cirsium hillii) and June Grass (Koeleria macrantha).