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The Rosaceae family.

The familiar rose is only a small part of the very large and complex Rose family. There are four sub-families with about a 120 genera and somewhere between 3000 and 4000 species. Rosa is the genus that comprises what we all know as the rose--probably about 120 species, with thousands of cultivated varieties. This article will focus on the woody genera within the Rose family that grow on the Canadian Prairies. The taxonomy of the rose family is ever evolving through research. The woody genera described are based on taxonomic lists in Alfred Rehder's "Manual of Cultivated Trees and Shrubs", 2nd revised edition, 1940 and on "Budd's Flora of the Canadian Prairie Provinces," 1987.

The sub-families are the spirea group (Spiraeoideae), apple group (Pomoideae), rose group (Rosoideae), and the cherry group (Prunoideae).

All the sub groups are linked to the rose family through common flower characteristics. The flowers are perfect usually with both male and female components present. In addition the flowers are almost always perigynous meaning that the petals, sepals and stamens occur surrounding the ovary. Botanically there are also finer structures of the flowers that link the sub-families together into the Rose family.

Spirea Group

Ninebarks (Physocarpus) shrubs are white-flowered, have three-lobed leaves and fruit called a capsule that turns showy red. Common ninebark (Populifolius) and the cultivars 'Dart's Gold' and 'Diablo' are widely available. Ninebark has been noted to produce a substance that inhibits the growth of weeds near its stems.

Spireas (Spiraea) are very showy shrubs with either white or pink flowers. Bridalwreath spirea (S. x vanhouttei) is well known for its arching branches of white flowers. Its stems require thinning out constantly to keep it tidy. Dwarf pink flowering spireas (S. x bumalda) include "Anthony Waterer' and 'Gold Flame' are extensively planted for their small size and colour. 'Gold Flame' has leaves with a dull yellow-orange colour with tinges of red. These spireas bloom throughout the summer, but the old flower heads must be pruned out regularly to stimulate continuous flowering. Japanese spirea (S. japonica 'Gold Mound') is noted for its compact form with light yellow leaves and small light pink flowers. All yellow leaved spiraeas growing in alkaline soils may develop chlorosis or iron deficiency. Untreated the leaves and twigs die from an anthracnose fungi infection. Chlorosis is treated by adding iron chelate to the soil.


Sorbarias (Sorbaria) are often called false spireas. Ural false spiraea (S. sorbifolia) is the only species planted on the Prairies. The plant produces long panicles of upright white flowers. It can can easily crowd any space it occupies, as it spreads rapidly through underground roots that send up suckering shoots, especially where they are not wanted.

Apple Group

Many genera of this group are represented on the Prairies. The fruits or pomes of this group consist of five capsules (called "cores") in a fleshy endocarp of the ovary.

Apples and crab apples (Malus) are widely distributed especially in urban gardens and farms throughout the southern Prairies.

Cotoneaster (Cotoneaster lucida) is a very common hedge species in Prairie parks and gardens. European species such as C. acutifolia and C. melanocarpa are occasionally found growing wild in woodlands near urban and farm homestead areas. Creeping cotoneaster (C. adpressus) is commonly planted for its prostrate form and red berries.

Hawthorns (Crataegus) are usually seen on the Prairies as small ornamental tree hybrids (C. x mordenensis). 'Toba' and 'Snowbird' are the most commonly available cultivars as they were once thought to be resistant to the Gymnosporangium rust diseases such as hawthorn-juniper gall rust and cedar-apple rust. Unfortunately ornamental hawthorn trees are dying throughout southern Manitoba especially from the hawthorn-juniper gall rust. The native woodland Prairie round-leaved hawthorn (C. rotundifolia) is the alternate host of the gall rust disease. This disease is weakening and killing large numbers of Rocky Mountain juniper (Juniperus scopulorum) cultivated varieties such as 'Medora' and 'Wichita Blue'. Ornamental hawthorns have also become alternate hosts for this disease.

Mountain ashes (Sorbus) in urban Prairie gardens are almost entirely represented by the European tree species (S. aucuparia). Fire blight disease has killed many thousands of these trees, and it is no longer recommended for planting. The native showy mountain ash (S. decora) with its bright red berries is sometimes planted in gardens as it is more resistant to fire blight.

Pears (Pyrus) are either ornamental or fruiting trees on the Prairies. Ussurian pear (P. ussuriensis) is the most common ornamental variety with its showy white flowers, but has no value as a fruit tree. Pear tree varieties such as 'Golden Spice', 'Early Gold' and 'Ure' are favoured for urban gardens.

Chokeberry (Aronia) is an introduced ornamental shrub from Eastern Canada. Occasionally the black or glossy chokeberry (A. melancarpa) with its shining black berries is planted in urban gardens in southern Manitoba.

Saskatoonberry (Amelanchier alnifolia) is a well known native edible berry shrub seen throughout the Prairies. They typically grow in wild shelterbelts and at the sunny edges of woodlands. 'Pembina' and 'Smoky' are common cultivated varieties. The native low service berry (A. humilis) grows in Manitoba's eastern forests. This species is known to hybridize with saskatoonberry in the wild.


Rose Group

Roses (Rosa) are complex groups of shrubs known to just about everyone. Only a few are mentioned here, as entire articles have been written about roses that grow on the Prairies. Three wild roses common to the Prairies are: the Prickly Rose (R. acicularis)--the provincial floral emblem of Alberta, Low Prairie Rose (R. arkansana) and Woods Rose (R. woodsii). R. arkansana has been intensively hybridized to produce the Parkland series of hardy shrub roses such as 'Morden Centennial' and 'Cuthbert Grant.' Rugosa rose (R. rugosa) is a commonly planted coarse-leaved rose with thick prickles. It too has been hybridized to produce cultivated varieties.

Raspberries (Rubus) are also a very large group of shrubs in the northern hemisphere. They are common berry shrubs in Prairie gardens. Wild red raspberry (R. idaeus var. aculeatissimus) is the most common shrub of its kind native to the Prairies. Several other species occur in boreal forest habitats.

Cinquefoils (Patentilla) are seemingly ubiquitous garden shrubs with many cultivated varieties P. fruticosa such as 'Coronation Triumph' having bright yellow flowers, 'Abbotswood' with white flowers, and 'Red Ace' with orange-red flowers. Most native potentillas are herbaceous, but shrubby potentilla (P. fruticosa sub species flaribunda) and three-toothed cinquefoil (P. tridentara) are woody on our Prairies.

Cherry Group

Cherry sub-groups (Prunus) are another very large, complex group of fruiting trees and shrubs consisting of cherries, plums, apricots, peaches and nectarines. The latter two fruit trees are not hardy to the Prairies. Wild chokecherry shrubs and trees (P. virginiana and P. var. melanocarpa) occur throughout Prairie woodlands. This species is highly susceptible to the pathogenic fungus commonly known as black knot disease. The ornamental Schubert chokecherry tree (P. virginiana 'Schubert') has leaves that turn maroon-purple from green during the summer, and frequently succumbs to the black knot disease. The introduced May Day tree (P. padus var. commutata) also is seriously affected by the same disease. Pincherries (P. pensylvanica) are also common native cherries.

Amur chokecherry (Prunus maackii) is not affected by black knot and remains a valuable ornamental tree. Its unique bark colouration and texture (orange-bronze and flaky or exfoliating) make it a popular choice for gardens. This tree does have a tendency to develop a prominent frost crack on the bark that can lead to infection by lethal pathogenic diseases. Observations in the eastern Prairies reveal this potential problem to be very minor.

Wild American plum (Prunus americana) and Canada plum (P. nigra) are common native plums, especially on the eastern Prairies. All wild Prunus species provide valuable food for many kinds of birds and mammals.

Prinsepias (Prinsepia) are represented by one species on the Prairies: cherry prinsepia (P. sinensis). This Asiatic species has abundant spines and produces many scarlet berries favoured by birds.

Michael Allen is a practicing certified arborist with Viburnum Tree Experts in Winnipeg, Manitoba, and a frequent contributor to The Prairie Garden.
COPYRIGHT 2008 This material is for informational use. Views are not those of the editorial committee. Reference to commercial products is made with no discrimination intended or endorsement by The Prairie Garden.
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Author:Allen, Michael
Publication:Prairie Garden
Geographic Code:1CANA
Date:Jan 1, 2008
Previous Article:The Wild, Wild Rose.
Next Article:Breeding hardier roses for the prairies.

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