Swamp Rose is an erect perennial shrub, growing 3 to 6 feet high, widely branching to about equal width, with smooth reddish arching stems that have stout thorns that have a wide base and a downward curve. On the upper stem, thorns are few and usually near leaf nodes, but the lower stem may have many prickles but less stout. New growth will be greenish before turning to reddish.
The leaves are alternate and pinnately compound with an odd number of leaflets, usually 3 pair of laterals and a terminal leaflet, but the number can vary from 5 to as many as 9 leaflets. The leaf stalk is reddish with fine hair. Each leaflet has a short stalk but occasionally only the terminal leaflet will be stalked. The leaflets are broadly elliptic with a central main vein and ascending lateral veins. Edges have serrated teeth but the lower 1/4th of the leaflet is usually without teeth. The upper surface is a darker green, the underside paler. The terminal leaflet and the the pair of laterals below the terminal leaflet will be the same shape but longer (up to 2-1/2 inches) and wider than those below. Leaflet tips are pointed. At the base of the leaf stalk is a pair of narrow stipules fused to the stalk except for the upper ends which diverge into pointed triangular tips.
The inflorescence is a single flower or a small cluster of stalked flowers at the tip of new growth.
The flowers are perfect, slightly fragrant, up to 2+ inches across with 5 pink petals, ovate to oval in shape, widest near the rounded tip. The receptacle or base, forms a cup-shape and has 5 calyx lobes (sepals) that are lanceolate in shape with long tapering tips. These are usually persistent on the fruit as it forms. The flower stalk, the receptacle, the underside of the calyx lobes are covered with reddish glandular tipped hairs. The reproductive parts in the corolla consist of the central yellow receptacle with densely clustered styles. The receptacle is surrounded by a ring of numerous stamens, flattened toward the petal surface. These have yellow filaments and slightly darker yellow anthers.
Fruit: Flowers mature to a smooth fleshy red rose hip, about 3/4 inch in diameter, that contains numerous achenes (the true seeds).
Habitat: Swamp Rose grows in the moist soils of marshes, swamps and riparian areas where there is adequate moisture, full sun, and typically more acid soils. The plant will tolerate some shade and can be grown in more upland sites if adequate moisture is provided. The root system is woody to woody rhizomatous with a tap root, and can produce suckering.
Names: The genus Rosa is Latin for 'rose'. The species name, palustris, means 'marsh-loving.' The author name for the plant classification, ‘Marshall’ is for Humphry Marshall (1722-1801), American Botanist, who published in 1785 - Arboretum Americanum: The American Grove, an Alphabetical Catalogue of Forest Trees and Shrubs, Natives of the American United States.
Comparisons: Many Wild Roses have similar appearances, especially in the flowers. Look for the amount and shape of prickles, the number of leaflets, the type of flower cluster and the presence or absence of glandular hair. Here is a comparison chart for 6 other wild roses that are native or can grow in Minnesota - Chart. Only the Carolina Rose and the Climbing Rose, R. setigera, have comparable glandular hair on the flower buds, calyx and receptacle. Swamp Rose is one of the latest blooming wild roses.
Above: The flowers of Swamp Rose are either singles or in a small cluster at the tip of new growth. Flowers are up to 2 inches across and fragrant.
Below: 1st photo - The flower receptacle, calyx and stalk are covered with glandular hair. 2nd photo - Old stems have reddish-brown bark. 3rd photo - The compound leaf has 5 to 9 leaflets. Note how the upper 3 leaflets are larger than those below.
Below: 1st photo - Leaflets have serrated margins except in the lower section. 2nd photo - At the base of the leaf stalk, which has fine hair, are a pair of narrow stipules fused to the stalk with divergent triangular tips. Prickles are generally in the are of a stem node, not dense, on the upper stems. More dense in the lower stem sections.
Below: 1st photo - Another view of the calyx. Note the long tips of the sepals. 2nd photo - The Rose hips are large - about 3/4 inch in diameter.
Below: The root forms a wood taproot with rhizomes which allow the plant to spread vegetatively. Some plants will lack the rhizomes.
Swamp Rose grows in the eastern half of North America, east from the Mississippi River states in the U.S., except Minnesota, and from Ontario eastward in Canada except Labrador and Newfoundland. The Mississippi River area states are at the very extreme western edge of its range. Even in Wisconsin it is known only in the very eastern part of the state. The U of M reports no information of its ever being found in the wild in Minnesota, although it will grow nicely here.
Five species of wild rose are recognized as being native to Minnesota, R. acicularlis, R. blanda, R. arkansana, R. woodsii and a cross between R. woodsii and R. blanda known as Rosa ×dulcissima Lunell (pro sp.) [blanda × woodsii]
References: Plant characteristics are generally from sources 1A, 32, W2, W3, W7 & W8 plus others as specifically applied. Distribution principally from W1, W2 and 28C. Planting history generally from 1, 4 & 4a. Other sources by specific reference. See Reference List for details.
Identification booklet for most of the flowering forbs and small flowering shrubs of the Eloise Butler Wildflower Garden. Details Here.
Friends of the Wild Flower Garden, Inc. Text and photos are by G. D. Bebeau unless otherwise credited. "www.friendsofthewildflowergarden.org"