Cattails and Other Wetland Plants of Toronto's High Park

Learn about the plants that grow along the shallow edges of High Park’s ponds and lakes, providing cover for fish and habitat for aquatic invertebrates and other wildlife.

Wetlands are home to a remarkable group of plants known as macrophytes — plants that grow in or near water. These include emergent species that rise above the surface, submergent plants that live entirely underwater, and floating plants that drift on the surface.

In the wetlands of Toronto’s High Park, macrophytes line the shallow edges of ponds and wetlands, creating vibrant, living shorelines. They play a vital role in the ecosystem by providing shelter for fish, habitat for aquatic insects and other wildlife, and food for many species. Just as importantly, they help maintain water quality by producing oxygen and stabilizing sediments.

American Sweetflag (Acorus americanus)

Perhaps the most significant wetland plant at Grenadier Pond is sweet flag, also known as calamus, a perennial member of the arum family. As an emergent plant, it grows in shallow water with its roots submerged while its leaves and stems extend above the surface. The name “sweet flag” comes from the plant’s distinctive citrus-like fragrance, released when the leaves are bruised or crushed, with an even stronger scent emanating from its rhizomes. These rhizomes are underground stems that function similarly to roots, producing both roots and shoots and allowing the plant to spread. The shoreline of Grenadier Pond supports extensive patches of this regionally rare sweet flag, making it an especially important species in this local ecosystem.

Sweet flag is commonly found in marshes, swamps, shallow open wetlands, and along slow-moving streams, thriving in calm, quiet waters. It plays an important ecological role, as muskrats often feed on its rootstocks while wood ducks consume its seeds.

The plant is easily recognized by its long, sword-shaped leaves, which range from 30-120 cm (10-50 inches) in length and have slightly wavy or curled edges. At first glance, sweet flag may be mistaken for cattail (Typha species), but it can be distinguished by its brighter green leaves and its unique flowering structure. In spring and summer, it produces very small greenish-yellow flowers arranged on a cylindrical spike known as a spadix, which is a key identifying feature of this plant. This spadix emerges from the side of a leaf-like flowering stem called a spathe and typically grows between 5 and 9 cm (2 to 4 inches) long. A spadix is a type of inflorescence in which many tiny flowers are densely packed together on a spike, a form also seen in other Ontario plants such as wild calla (Calla palustris) and Jack-in-the-pulpit (Arisaema triphyllum). Another identifying characteristic is the plant’s pleasant fragrance, which becomes noticeable when the leaves are crushed.

Although sweet flag produces flowers, it is generally infertile and does not produce viable seeds. Instead, it reproduces vegetatively through its rhizomes, forming dense groves over time.

Historically, all sweet flag in North America was classified as Acorus calamus, an introduced Eurasian species, but more recent research suggests the presence of two species: Acorus calamus and the native Acorus americanus. The population at Grenadier Pond has been confirmed as Acorus americanus. DNA evidence indicates that Acorus represents one of the oldest surviving lineages of monocots, offering valuable insight into early plant evolution and providing paleobotanists with a living window into the distant past.

Broad-leaved Cattail (Typha latifolia)

Broad-leaved cattail is a common emergent plant found in freshwater marshes, shallow waters, and even roadside ditches where water is available. Its stiff stems and upright, blade-like leaves provide convenient resting and nesting sites for birds. Cattails play an important ecological role by stabilizing shorelines, offering shelter for fish, and creating habitat for aquatic invertebrates. Through photosynthesis, they also contribute oxygen to the water and help filter runoff, improving overall water quality.

The plant takes its name from its distinctive cylindrical brown fruiting spike, which develops in late summer. Growing up to about 2 metres (6–7 feet) tall, the cattail features a dense, sausage-like cluster of pistillate (female) flowers near the top of the stem. Just above this sits a narrower section of lighter-colored staminate (male) flowers that release pollen, which falls onto and fertilizes the female flowers below. As fall and winter progress, the fertilized seed head gradually breaks down, releasing countless tiny, fluffy seeds that are carried away by the wind.

For Indigenous peoples and early settlers, cattails were often described as a “wild supermarket” because of their many practical uses. The roots were eaten raw, cooked in soups, or ground into flour for making bread and pancakes, and they remain a valuable survival staple food. The tough, fibrous leaves were used to weave mats, baskets, bags, and even clothing. In the past, the soft, cotton-like fluff from the seed heads was used as stuffing for bedding. Today, cattail stands continue to support wildlife: birds use them for nesting and perching, while muskrats build their lodges from their leaves. The plants and their associated microorganisms also contribute to water purification by helping to break down organic pollutants.

However, cattails face growing competition from the highly dominant introduced Phragmites species or common reed (Phragmites australis). In many areas, especially urban environments, phragmites can outcompete and replace native cattail populations. Its tolerance for higher levels of pollution makes it particularly difficult to manage, posing an ongoing challenge for wetland conservation and restoration efforts.

Phragmites in High Park

Phragmites australis is a highly dominant species capable of displacing native plants and reshaping entire ecosystems. Three strains occur in North America: one native and widespread that coexists with other species, one native to the southern United States, Mexico, and Central America, and a third introduced from Europe in the 1800s which is most widespread and aggressive. Its appearance in High Park’s Grenadier Pond is relatively recent, and it can now be found in every Canadian province.

Wide-leaved/Broad-leaved/Common Arrowhead (Sagittaria latifolia)

This common perennial emergent wetland plant that blooms in summer with striking white flowers measuring 2–4 cm (¾–1½ inches) across. These flowers are arranged in whorls of three on a separate flowering stalk. At peak bloom, each flower features a dense cluster of approximately 25–40 fuzzy, yellow, pollen-producing stamens at its center. The plant’s leaves are distinctly arrow-shaped, glossy green, and highly variable ranging from broad to narrow forms, and can reach up to 40 cm in length. Their leaf petioles are typically long and vary in length. Stems are smooth with a mature height of roughly 20 to 120 cm (8–47”) above the water surface. Common arrowhead thrives in shallow, open water wetlands and marshes, usually in depths of 10–15 cm (4–6 inches), and belongs to the Water Plantain family.

One of its most notable features is its rhizomes, which produce edible tubers commonly referred to as “duck potatoes,” a name often used interchangeably with Sagittaria latifolia. These starchy tubers develop beneath the water in the plant’s root zone and serve as an important food source for wildlife, including muskrats, geese, and other local species. Historically, both Indigenous Peoples and early European settlers harvested and consumed these tubers. Indigenous communities were even known to seek out muskrat lodges, where stores of arrowhead tubers could often be found, as muskrats are among the plant’s primary consumers.

Common arrowhead also plays a significant ecological role in improving water quality. It is particularly effective at absorbing and retaining excess nutrients such as phosphorus, as well as certain heavy metals. In urban and agricultural landscapes, phosphorus commonly enters surface waters at concentrations of approximately 20–30 µg/L, contributing to nutrient pollution. Elevated phosphorus levels can trigger eutrophication, leading to algae blooms that deplete dissolved oxygen in the water upon decomposition, thus creating harmful conditions for other aquatic life. By helping to remove and store these nutrients, Sagittaria latifolia acts as an important natural filter within wetland ecosystems.

Blue Flag Iris (Iris versicolor)

The perennial Blue Flag Iris thrives in consistently moist to wet environments, including marshes, pond and lake margins, swamps, wet meadows, and even roadside ditches. In June, it produces abundant, striking flowers that range from violet to deep blue and measure 6–10 cm (2–4 inches) across. Each bloom features gracefully drooping sepals marked with darker blue-violet veins and a prominent yellow “tongue” that serves as a landing platform for pollinating insects. Three upright petals rise from within the arching sepals, creating a delicate yet structured form. Its leaves are long, narrow, and sword-like, typically 20–80 cm (8–32 inches) in length and up to 3 cm (1¼ inch) wide.

Iris versicolor has notable antimicrobial properties and has been used traditionally by Indigenous cultures to treat skin conditions and as a topical analgesic. The plant is known to inhibit harmful bacteria such as E. coli, releasing antibacterial compounds from its roots into surrounding water. These antibacterial benefits also makes it toxic to humans and some wildlife, and its roots in particular are poisonous and should not be ingested.

Blue Flag Iris is highly attractive to pollinators, including bees, butterflies, and the Ruby-throated Hummingbird (Archilochus colubris), which visit the flowers for nectar. Its roots are also occasionally consumed by muskrats.

This plant should not be confused with Yellow Flag Iris (Iris pseudoacorus), an increasingly dominant introduced species native to Europe and Asia. Although still sold in some nurseries, Yellow Flag Iris can aggressively spread and displace native wetland vegetation, and is best avoided as water garden ornamental plantings.

Please Stay On Official Trails

Wetland plants are especially sensitive to disturbance, and even small impacts can harm these delicate ecosystems. Grenadier Pond and other wetlands in High Park are also considered a Provincially Significant Wetland due to its ecological and wildlife importance. When visiting High Park’s ponds and marshes, please stay on designated trails and observe from a safe, dry distance. Avoid stepping into wet areas or picking plants, as this can damage important habitat and disrupt wildlife. By enjoying these spaces responsibly, you help protect the health and beauty of the wetlands for plants, animals, and future visitors alike.