Rosa acicularis

Rosa acicularis is a deciduous shrub growing 1–3 m tall. The leaves are pinnate, 7–14 cm long, with three to seven leaflets. The leaflets are ovate, with serrate (toothed) margins. The flowers are pink (rarely white), 3.5–5 cm diameter; the hips are red, pear-shaped to ovoid, 10–15 mm diameter.

The ploidy of this rose species is variable. Botanical authorities have listed it as tetraploid and hexaploid in North America (subsp. sayi), and octoploid in Eurasia (subsp. acicularis). On the northern Great Plains and in northwest Canada, extending to Whitehorse, Yukon its populations are generally tetraploid.

Propagation                                        

Seed. Rose seed often takes two years to germinate. This is because it may need a warm spell of weather after a cold spell in order to mature the embryo and reduce the seedcoat. One possible way to reduce this time is to scarify the seed and then place it for 2 - 3 weeks in damp peat at a temperature of 27 - 32°c (by which time the seed should have imbibed). It is then kept at 3°c for the next 4 months by which time it should be starting to germinate. Alternatively, it is possible that seed harvested 'green' (when it is fully developed but before it has dried on the plant) and sown immediately will germinate in the late winter. This method has not as yet(1988) been fully tested. Seed sown as soon as it is ripe in a cold frame sometimes germinates in spring though it may take 18 months. Stored seed can be sown as early in the year as possible and stratified for 6 weeks at 5°c. 

It may take 2 years to germinate. Prick out the seedlings into individual pots when they are large enough to handle. Plant out in the summer if the plants are more than 25cm tall, otherwise grow on in a cold frame for the winter and plant out in late spring. Cuttings of half-ripe wood with a heel, July in a shaded frame. Overwinter the plants in the frame and plant out in late spring. High percentage. Cuttings of mature wood of the current seasons growth. Select pencil thick shoots in early autumn that are about 20 - 25cm long and plant them in a sheltered position outdoors or in a cold frame. The cuttings can take 12 months to establish but a high percentage of them normally succeed. Division of suckers in the dormant season. Plant them out direct into their permanent positions.

Cultivation details
Succeeds in most soils, preferring a circumneutral soil and a sunny position. Prefers a slightly acid soil. Grows well in heavy clay soils. Dislikes water-logged soils. Grows well with alliums, parsley, mignonette and lupins. Garlic planted nearby can help protect the plant from disease and insect predation. Grows badly with boxwood. Hybridizes freely with other members of this genus. Produces its fruit abundantly in Britain. This plant is the floral emblem of Alberta. Plants in this genus are notably susceptible to honey fungus.