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Identifying Manitoba's native roses.

The Manitoba native roses are generally fairly easy to recognize as low to medium sized herbaceous shrubs combined with scented red to pink flowers (with an occasional white), bearing prickles on the majority of species and colourful reddish hips in the fall.

According to Scoggan (1957), Looman and Best (1979) and Cody (1988) there are four native species of roses in Manitoba: Rosa acicularis, Rosa arkansana, Rosa blanda and Rosa woodsii. Scoggan (1957) reports variation within each of the species while Voss (1985) indicates hybridization occurring between some of the species. With local variations in form being common, authorities do not necessarily agree on nomenclature and the genus may present some difficulty in classification.

The native species grow as herbaceous deciduous shrubs and can generally be readily classified on the basis of plant characteristics that include the prickles, leaf, flower form and colour, period of bloom, the fruiting hips and stem hardiness.

The prickles, which are fairly common in Rosa species are small, more or less slender, sharp outgrowths from the stem cortex and epidermis (Raven et al, 1999) whereas thorns are defined as modified branches that arise in the axils of the leaves. The authors further indicated that "The so-called thorns on rose stems are prickles." Harris et al, 2001, defines a thorn as a "stiff, woody, modified stem with a sharp point."

Depending on the weather, all species bloom approximately June to July with R. arkansana being the latest to flower.

Rosa acicularis or the Prickly Rose is fairly common, being generally found in bluffs and around woods, along roadsides, rock outcroppings, fields and clearings throughout the province extending to just south of Churchill. It is also known as a circumpolar species prevalent through North America and Northern Europe, Russia, China and Japan.

The Prickly Rose is generally easily recognized by the high density of prickles extending from the base of the stem to the tip of the flowering branch. This species as well as Rosa arkansana and R. blanda grow from one to two meters in height. R. acicularis can have three to seven leaflets, but often has five. This early blooming rose generally has a single fragrant flower on each stem varying from a pink to a deep rose colour. The hip, which is the first of the four species to ripen, differs from other species in that is pear shaped (pyriform) with the sepals extending out in front of the hip.

Rosa acicularis is also the floral emblem for the province of Alberta proclaimed in 1935 by an act of the provincial legislature, even though R. arkansana and R. woodsii have a wider distribution in the province.

Rosa blanda, the Smooth Rose and R. woodsii or the Woods Rose are found in thickets, clearings, along wood edges and shores in the southern two-fifths of Manitoba.

Both species flower with three to seven blooms per inflorescence.

Rosa blanda, in contrast to the Prickly Rose, has stems that have little or no prickles notably on the canes. This rose has five to seven and sometimes up to nine leaflets. The flower may be a single bloom or several in a small corymb (a flat-topped or round-topped inflorescence, but with the lower pedicels longer than the upper) varying in colour from pink to white.

Rosa woodsii can generally be defined by the prickles found at the base of the stipules. The stems are covered with prickles that extend to the flowering stem, however, they are not as dense as that found in R. acicularis.

Rosa woodsii has five to nine elliptical-obovate leaflets with flowers mostly corymbed about 3 cm across varying in colour from pink to white.

Rosa arkansana, the Low Prairie Rose and fourth species in Manitoba occurs on hills, roadsides and clearings in the southern quarter of the province (Scoggan, 1957) with the most northerly collection being found near Gypsumville. This rose, as the name reflects, is the shortest species, growing from 0.3 to 1 meter in height. It bears three to seven, but generally five leaflets, while the hips are round with the sepals reflexed to the back. The stems on the Low Prairie Rose generally tend to die-back annually.

Rosa arkansana is distinct from the other three species in that it blooms later and on new growth in addition to the older wood. All other species bloom on older wood only.

The flower may vary from either a single inflorescence to a large stem with many blooms ranging in colour from white to deep pink.

In summary, the four species can be fairly easily identified based on their characteristics.

Rosa acicularis or the Prickly Rose has a high density of prickles and would be difficult to handle without gloves; R. blanda or the Smooth Rose in contrast has very little if any prickles; R. woodsii or Woods Rose has a prickle at the base of the stipules and R. arkansana or the Low Prairie Rose is noted for being quite short with some annual die-back of the stems.

References:

Cody, W.J. 1988. Plants of Riding Mountain National Park. Research Branch, Agriculture Canada. Publication 1818/E. Canadian Government Publishing Centre, Supply and Services Canada. 319 p.

Harris, J.G. and Harris, W.F. 2001. Plant Identification Terminology, An Illustrated Glossary. Second Edition. Spring Lake Publishing, Spring Lake, Ytah. 206p.

Looman, J. and Best, K.E 1979. Budd's Flora of the Canadian Prairie Provinces. Research Branch, Agriculture Canada. Publication 1662. Canadian Government Publishing Centre. Supply and Services Canada. 863 p.

Raven, EH., Evert, R.F. and Eichhorn, S.E. 1999. Biology of Plants. Sixth Edition. W.H. Freeman and Company. Worth Publishers. 944p.

Scoggan, H.J. 1957. Flora of Manitoba. National Museum of Canada. Bulletin No. 140. Department of Northern Affairs and National Resources. 619 p.

Voss, E. G. 1985. Michigan Flora. A guide to the Identification and Occurrence of the Native and Naturalized Seed-Plants. Part II. Dicots (Saururaceae-Cornaceae). Bloomington Hills, MI: Cranbrook Institute of Science.

Ed Czarnecki conducted wheat breeding research for Agriculture and Agri-Food Canada for 28 years before taking an early retirement. Now, among other things, he is pursuing his interests in photography and gardening, breeding lilies and a number of other perennials.
Prairie Rosa species of Manitoba

Botanical                                    Rosa
name            Rosa acicularis            arkansana

Common           Prickly Rose             Low Prairie
name                                         Rose

Height             30-120 cm               20-30 cm

Prickles      very dense prickles
              from base to almost        fairly dense
              the flowering stem           prickles

Leaflets/   5-9, hairy, elliptical,      9-11, usually
Leaves          simple serrate          without hairs,
                                         20-50 mm long

Flower        pink, single 5-7 cm          pink, in
                    across              corymbs 1, 2 or
                                         three blooms

Stems                                      die back
                                           annually

Stipules     broad, usually hairy,
                   glandular

Fruit         ovoid, constricted       almost globular,
                  neck 15 mm,              12 mm in
                pyriform (pear)            diameter

Botanical         Rosa blanda            Rosa woodsii
name

Common              Smooth                Woods Rose
name                 Rose

Height             60-120 cm               50-200 cm

Prickles         few prickles           prickles below
               confined to base        stipules usually
                of stem or only          well defined
                scattered above

Leaflets/     5-7 leaflets, 25-40        5-9 leaflets,
Leaves         mm elliptical to            15-35 mm
                 oblong-ovate,         elliptical-ovate,
                    serrate            coarsely serrate

Flower           pink, to 7 cm         pink or white, 2-
              across single or in      5 cm 1 or several
                a small corymb            in a corymb
                                         borne on 2nd
                                         year branches

Stems

Stipules        stipules rather        prickles present
                     broad              below stipules

Fruit          subglobose, 10-15       globular without
                mm in diameter           a constricted
                                             neck
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Author:Czarnecki, Edward
Publication:Prairie Garden
Geographic Code:1CMAN
Date:Jan 1, 2008
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