Shirley Heinze Snapshot 5: The Great Marsh, August 1, 2023

By Dale K. Nichols (Board Member)

Dear friends of Shirley Heinze Land Trust:  This is the fifth in a series of “snapshots” featuring our Beverly Shores/Great Marsh preserve.  It will focus on some of our lovely native marsh plants (the “good”) and their non-native or invasive cousins (the “bad” and the “ugly”).  Because all of these plants are known by a variety of common names, for clarity I will stick here to their botanical names.

BLUE FLAG (Iris virginica var. schrevei) vs. YELLOW FLAG (Iris pseudoacorous)

Both Iris virginica var. schrevei and Iris pseudoacorous are members of the Iris family.  They are most easily distinguished by the color of their flowers (blue/purple vs. yellow), which usually begin blooming in this area of the country in late April to early June.  Iris virginica var. schrevei is native to eastern North America, while Iris pseudoacorous is a non-native invasive plant that grows naturally in Europe, western Asia and North Africa.  Both plants are found primarily in wetland habitats like the Great Marsh.  Iris pseudoacorus was likely introduced here by local gardeners.  It can be found in abundance in the drainage ditches that adjoin town streets running through and around the marsh.  There are several large patches of Iris virginica var. schrevei (Blue Flag) on the east side of Wells Street (just north of Beverly Drive), with smaller patches on the east side of Constance (near Idler) and elsewhere.

SWAMP ROSE (Rosa palustris) vs. MULTIFLORA ROSE (Rosa multiflora)


Both Rosa palustris and Rosa multiflora are deciduous shrubs and members of the Rose family.  Rosa palustris is native to eastern North America, while Rosa multiflora is an interloper native to East Asia.  Rosa palustris grows primarily in wetland habitats; Rosa multiflora is highly adaptable and can grow in a much wider range of habitats.  Rosa multiflora was introduced to North America in the 1860s, first as a rootstock for ornamental roses, and later for erosion control, wildlife habitat enhancement, and as a hedge plant.  It is highly invasive, forming dense thickets that outcompete native vegetation, reducing biodiversity.  Rosa palustris shrubs typically grow straight up to a height of 3 to 6 feet, while Rosa multiflora can reach heights of up to 15 feet, often arching to be ground if not supported by a tree or shrub.  Both plants typically bloom in late spring to early summer in northwestern Indiana.  The flowers of Rosa palustris are typically pink to deep rose in color, and they have large, showy blooms with five petals and a noticeable cluster of yellow stamens in the center.  By contrast, the flowers of Rosa multiflora are smaller, white or cream-colored, and are arranged in clusters, giving the plant a dense, showy appearance when in bloom.  The thorns of Rosa palustris are generally smaller, straighter, and less dense than those of Rosa multiflora.  The curved thorns of Rosa multiflora aid the plant in climbing and spreading over other vegetation.  Both Rosa palustris and Rosa multiflora can be found throughout the Great Marsh, despite efforts to control the latter.

AMERICAN PHRAGMITES (Phragmites australis subsp. americanus) vs. AUSTRALIAN PHRAGMITES (Phragmites australis subsp. australis)

Also commonly referred to as the American Common Reed, Phragmites australis subsp. americanus is native to North America.  Subsp. australis, which is also often called European Common Reed, is native to Europe and is believed to have been introduced by to the Americas by accident in the 18th or 19th century, after which it quickly spread across the continent.  Here are a few key differences between the two subspecies.

  • americanus does not normally form dense monocultures; australis does, spreading rapidly from both rhizomes (horizontal underground stems) and stolons (horizontal stems that grow along the soil surface) which can grow up to 50 feet long and more than 4 inches a day
  • australis is more densely flowered than americanus and has tougher stems that do not deteriorate very rapidly, a stand becoming a dense mix of old and new stems
  • americanus does not generally exceed 7 feet in height,; australis may reach 15 feet or more
  • americanus leaves are green to yellowish-green; australis are blue-green
  • americanus lower to mid stems are smooth, somewhat shiny and maroon to chestnut colored; australis stems are ribbed and roughish, dull green to tan

BLUE JOINT GRASS (Calamagrostis canadensis) vs. REED CANARY GRASS (Phalaris arundinacea)                                                                                                                                             

Both Calamagrostis canadensis and Phalaris arundinacea are perennials and members of the Grass family, though in different genuses.  While Calamagrostis canadensis is native to North America, Phalaris arundinacea is native to Eurasia and has been introduced to various parts of North America.  Calamagrotis canadensis typically grows in clumps, reaches a height of 2 to 5 feet, and has bluish-green or bluish grey upright stems and long, narrow, flat leaves.  Phalaris arundinacea, on the other hand, is taller, ranging from 3 to 9 feet in height, forms dense stands, has round and hollow stems, and long, flat, coarse leaves with serrarted edges.  While Calamagrostis canadensis plays an important ecological role in wetland habitats, providing cover and food for wildlife, Phalaris arundinacea can be invasive and can have negative impacts on native plant diversity, having a tendency to outcompete native species and to form dense stands that can reduce biodiversity in some ecosystems.

Stewardship staff has successfully brought the population of Phragmites australis subsp. australis and Phalaris arundinacea under control in our stretch of Great Marsh property running from McAllister on the west to the block east of Wells.  A few patches of (the “good”) subsp. americanus remain, and Calamagrostis canadensis (Blue Joint Grass) is now thriving.